· COAL GAS B Y- PRODU CTS. I NTRODUCTI ON . THE gas which issues when a gas burner is turned on...

THE BY-PRODUCTS

COAL-GAS MANUFACTURE

K. R. IrANGE ; PH .D .

TRAN SLATED FROM THE GERMAN BY

CHAS. SALTER

WI TH TH I RTEEN I LL US TRATI ON S AND D I AGRAMS

LONDON

S C O T T,G R E E N W O O D S O N

8 BROADW AY,LUDGATE

,E C .

1 9 I 5

[ The sole r ig/Zn of tr ans la tion into E rig/£512 r ema in with

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D. VAN NOSTRAND COMPANYNEW YORK

TABLE OF CONTENTS

INTRODUCTION

CHAPTER I

PURIF ICATION OF COAL GAS

CHAPTER IICOKE

CHAPTER IIIRETORT GRAPH I TE

CHAPTER IVGAS TAR

C APTER VTHE GAS L IQ UOR

Test ingGas L i quorT r eating th e Gas L i quorTh e D ist i l lation of Gas L i quorWor king th e S til lPr epar ation of Concentr ated Gas LiquorPr eparat ion of Ammon iaL iquefied Ammon iaSu lph ate of Ammon ia

CHAPTER VITHE TREATMENT OF THE GAS -PURIFYING AGENTS

E l iminat ing th e Su l phu r by E xtract ionL ix iviat ing th e Pur i fy ingMateria lTr eat ing the L iquorTr eating th e E xt racted Mater ial

V

v i TABLE OF CONTENTS

CHAPTER VI I

TREATING THE CYANOGEN SLUDGE

CHAPTER VI I ITREATING THE CRUDE LIQ UORS

1 . Pr ec ip itation w ith I r on Salts2 . P rec i p itation with Ammon ium Salts3 . Pr ecip itat ion W ith Potassium Sa lts

CHAPTER I X

THE TREATMENT OF CRUDE AMMON IUM TH IOCYANATE ANDCUPROUS TH IOCYANATE

CHAPTER X

POTASS IUM FERRICYAN IDE

C APTER X I

THE CYANOGEN PIGMENTS

CHAPTER XI I

SULPH UR AND SULPH URIC ACID

INDEX

COAL GAS B Y -PRODU CTS .

I NTRODUCTI ON .

THE gas which issue s when a gas burner i s turnedon is not th e on ly product furnished by th e dry d istil lation of coal , th e crude gas , as it leaves th e r e

torts,contain ing substances th e combustion of which

has an unsalutary effect on the human organism,so

that these substances must be removed from th e gas

before i t reaches th e consumer . The bodies in quest ion ar e

,chiefly , sulphuretted hydrogen ,

hydrocyanicacid and ammon ia .

Th e distillation Of coal i s conducted at a very hightemperature and some of th e gaseous products thu sformed do not remain in th e state Of gas at the or

dinar y room temperature . Con sequently , a partialcondensation of th e gaseous mixture occurs on th e

way to the gasholder , Coal—tar and gas l iquor beingdeposited . The ir complete separation is effected bysuitable cooling , in order to preven t Obstruction inthe pipes . Naphthalene

,in particular

,tends to

Choke up the pipes to an unpleasan t extent in coldweather , by crystal lization . Th e substances to beregarded as the r aw material Of th e by-products inCoal-gas making ar e th e coke and graphite left in th e

retorts , and the tar, gas l iquor , sulphuretted hydro

gen and hydrocyanic acid in th e d isti llate . As coal

a, n \

.

OGALHAS B Y-PRODUCTS

gas there remain hydr ocarbons , carbon monoxide and

carbon dioxide .

Th e re lative proportion s of these various constituents dependp n the temperature , th e

/

ar r angemen t Of

th e retorts and the length Of th e gasifying period .

At present , coal i s usual ly distil led at 1100-1300° C .

With regard to the relative proportion s of th e constituents Of coal

,very extensive experimen ts were

carried on by Dr eh schmidt in 1904 with the exper i

mental plan t at the Berlin mun icipal gasworks , at

Tegel . Since this plant is con structed to scale and

model led on the l ines of practice , the experimentsfurnish an accurate i l lustration of the percentage composition Oi th e gasification products . Th e followingtable gives th e maximum and minimum value s inth e case Of sixty -eight kinds of coal and the gasification products Of same . Th e moisture con ten t ofth e r aw coal was 2 per cent . The percentage Ofgas

l iquor is confined to the amoun t Of water producedduring distillat ion . The gasifiable sulphur could notbe determined direct

,but was calculated from th e

difference between the original sulphur in th e coaland that found remain ing in the coke .

The experiments show that th e percen tage con ten tof cyanogen and ammon ia i s independent Of the

origin and composition Of the coal ; but that th esulphur

, on th e other hand , i s general ly more abundan t in English coals . Before going in to th e treatmen t of th e recovered substan ces , brief consideration

,

may be given to the gas works , to gain some idea ofhow the substances men tioned above ar e eliminatedfrom th e gas .

INTRODUCTION

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CHAPTER I .

PURIFICATION OF COAL GAS .

TH E crude coal gas passes from th e retorts throughupcast and trapped pipes into a mping - receiver (thehydraulic main ) in which th e heaviest condensationproducts Of the tar , and a portion of the gas l iquor ,begin to separate out . Next follows a tubular orannular apparatus in which the gas i s cooled , by air

,

to a temperature Of about 40°

C . (104°

E ) , and i sthus caused to part with the bulk of the containedwater

,part of the ammonia

,and most Of th e res idual

tar . The gas i s th en put through a process of wetpurification which remove s the bulk Of th e ammon ia

,

and part -Of th e sulphuretted hydrogen and cyanogen ,

by absorption . On th e coun ter-flow principle,the

gas i s introduced in to th e bottom of cylindricalvessel s

,down which water is allowed to flow from

above . I n order to presen t a large wetting surfaceto th e gas , superimposed gratings ar e laid on barsat in tervals in th e interior of th e cylinder

,or e l se

prismat ic bars ar e laid over one another cross:

wise . I n place Of these upright cylinders , orscrubbers , inclined cylinders ar e now sometime s

(4)

PURIFICATION OF COAL GAS 5

used . These ar e fi l led about one-third full of water ,a horizontal rotary shaft carrying bars with faggotsof wood bringing the gas into intimate con tact withthat l iquid . By th e aid Of a suction and pressure

apparatus , the gas i s de livered to the purifying boxesfor the dry treatment . These boxes ar e rectangularand ar e provided at th e upper rim with a groove inwhich the lid engages , a tight joint being made byfi lling th e groove with water . Th ese boxes also ar eprovided with gratings on which the purifying agen ti s loose ly spread . The gas enters the box at a suitable point

,flows through th e interior and issues at

the opposite side . TO ensure complete purification ,

several boxes ar e arranged in series . I n thi s caseal so th e counterflow system has been found sati sfactory , the fresh gas being brought in to contactwith th e purifying material which h as been mostused , and th e almost complete ly purified gas passing through fresh material . When th e purifyingmaterial i s no longer capable of taking up any moresulphuretted hydrogen

,it i s regenerated , th e iron

sulphide formed being reconverted into ferric hydr oxide by atmospheric oxygen and moisture , whilstsulphur separates out . Repeated tur n ing over witha shove l facilitates the process and prevents localheating through th e heat generated by th e reaction .

Th e material regenerated in this way i s used overagain , unti l final ly it has become so impregnatedwith sulphur that its value as an absorben t has sunkvery low , whereupon it i s put aside to be treated forth e recovery of its valuable con stituen ts . By th e

6 COAL GAS BY-PRODUCTS

above treatment the gas is freed from most of i tsin jurious con stituen ts

,and i s then passed on to the

gasholder,for distribution in the main s . Whilst the

reaction s in th e wet purification process ar e Simple,

those Of the processes in th e purifying boxes ar e Of

a complex nature,and have been the cause of much

divergence of Opin ion among experts .

I n th e wet proce ss,ammon ia

,sulphuretted hydro

gen and hydrocyan ic acid pass directly into solution .

A small portion Of th e sulphuretted hydrogen i soxidized by th e oxygen present , so that oxygen compounds of ammonia ar e found in th e gas liquor .Pfei

""

er detected th e fol lowing products in gas liquorfrom th e Magdeburg gasworks

Total ammonia 19 35 per cent

Comb ined ammon ia 0 642

Fr ee ammonia

I f th e combined ammonia be al located to the acidsabsorbed in th e gas l iquor , th e following values ar e

Obtained :

Ammon ium car bonateAmmon ium su lphydr ateAmmon ium th iosu lphat eAmmon ium su lphateAmmon ium th iocyanateAmmon ium fer r ocyan ide

I nformation as to th e d istribution of these con

stituents in th e different absorpt ion apparatus is

afforded by th e researches of Lunge and Cox

1 293 per cent

0086

01 78

0 1470034

PURIFICATION OF COAL GAS

5 g;m

02

A s s 5 332-3 mas s 3 5 5 5 .

Ammoma m 50 2 -51g 0 5 2 mp g 0 4: g 2 3 a,

"

G r ins. per gr , < 0 : a g‘ o fi gs g aw 9 -5 £ 5Litr e, as C ? 8

2 3 80

'

s 80 2 0 ? E

OE 8? as“

s d h 0 8 0 5 0 8 8 0 o fi o 0 5 8 3mt & “

o 2“ o 8 90 "

“O 8

Tota lPer centage of

stab le salts 59 56 18 4 2

Sp . gr . at

15 6°C. 10 11 10 12 1035 107 5 11 15 1-120 1-022 1-010

The amount Of these salts natural ly varies ac

cording to the origin Of the coal,th e sulphur com

pounds con taining a higher percentage Of th e

ammonia in the case Of coals high in sulphur . The

con struction and arrangement Of th e retorts al soaffect the ammonia content Of the gas l iquor . Thus ,Carpenter Obtained the values shown on n ext pagefor horizon tal , sloping , and vertical retorts respective ly .

Since the absorption of the hydrocyanic acid , inthe wet process as detai led below

,is e

'"

ected pr e

vious to the absorption of the ammonia in purifyingth e gas , it naturally produces changes in th e per

cen tage composition of the gas l iquor . On thispoint informat ion i s afiorded by th e va lues Obtainedin comparative experiments by Linder , which Show


<67:22 Ammon ia Grms per 53

53z is j 33 Litr e .

9

Gas Liquor 5873 “if ”305 gas 2 43

fr om Re gamg $3 n gtor ts '

513a; ga Readily (

ii-4 <5 4 H

cu a S E E Total . Decom Stab l e. o‘ o

o 5f“O(3 O (5 posab l e . O E" m

Hor izontal 3 13 34 68 3 84 O3 4

S loping tr ace 5 23 369 6 0 17

Ver tica l tr ace 13 28 13 86 0 50

that th e removal of cyanogen as a preliminarytreatmen t

,lowers the percentage Of cyanogen

,

hydrocyanic acid and ammon ia,but considerably

increases th e proportion Of sulphate . On ly smal lquan titie s of th e cyanogen compounds present inthe gas ar e

'

absorbed during the wet purification,

th e reason being that the gas con tains su“

cientcarbon d ioxide to preven t the formation of am

monium cyanide . Leybold found that 8 -02 per

cent of the total hydrocyanic acid was removed inthe cooling process , and 65 5 per cen t in the

scrubbers .Th e main Object of the dry treatment is the

removal Of sulphuretted hydrogen ; and i t is on lyof late years that importance has also been attachedto a thorough absorption Of the hydrocyanic acid as

we l l , on recogn izing th e latter as being an injuriousconsti tuent Of coal gas . At th e same time it con

sider ably improves th e value Of the spent purifyingmaterial s

,and he lps to recoup the cost of pur ifying

th e gas through the sale Of the e liminated constituents . The Older methods of freeing gas from


CONSTITUENTS OF GAS L IQ UOR : GEMS . PER LI TRE .

With ou t Re Wit h Removalmoval of th e of the

,

Cyanogen . Cyanogen .

Ammon ium fer r ocyan ideCh lor i de cal . as EZCl

Carbon dioxideSu lph ur etted hydrogenHydrocyan ic acidAmmon ia :

r eadily decomposab lestabletota lAl locat ion of th e Su l :ph ur

as su lph ide 72 8 per cen t 33 5 per cent

as su lphate per cent 23 9 per cent

as th iocyanate 234 per cent 22 4 per cent

as su lph i te and th iosu lph ate 3 1 per cen t 122 per cen t

sulphuretted hydrogen employed milk Of lime , thisbe ing afterwards replaced by dry quicklime . Thismethod

,however

,was abandoned as long ago as the

s ixties and i s now employed only in England . Th e

first e ffect Of quicklime is to absorb th e carbond ioxide in the gas , the carbonate thus formedthen combining with the sulphuretted hydrogen toform calcium sulphydrate . Th e hydrocyani c acid i schiefly retained in th e form of calcium th io cyanate .

Laming in troduced materials con tain ing ferric oxideas absorbents for sulphuretted hydrogen

,using an

artificial preparation which stil l contained some

lime . Later on,however

,it was found that th e

material could be regenerated by exposure to air,

even without addition Of lime . As already men

tioned,con siderable divergences of Opin ion prevai led


on the subject Of th e absorption processes ; but sincea discussion Of these views would be outside the

scope Of the p resent work , further reference in thisconnection may be confined to B er teslmann

’

s reviewOf th e question .

According to th e view of that authority,

“ th e

absorption of sulphuretted hydrogen by th e ferrichydroxide of the purifying material is largely accom

panied by th e formation Of iron sesquisulph ide . A

portion of th e ferric -hydroxide i s reduced by th e

conjoin t action Of sulphuretted hydrogen and am

mon ia,so that ferric sulphide i s formed , together

with free sulphur,th e exten t Of this reduction

varying directly with the amoun t Of ammon iapresen t .

Th e hydrocyan ic acid in the gas i s not absorbedby material s which do not contain ferrous oxide ,

the absorption not commencing un ti l th e hydroxidehas been reduced by sulphuretted hydrogen and

ammonia .

Regenerated material absorbs hydrocyanic ac id ,owing to th e formation of ferrous hydroxide in th e

regenerative process,which hydroxide i s not fully

converted into th e ferric condition . The cyanogenis contained in th e purifying material as ironcyanide compounds and ammon ium thiocyanate .

Thiocyanogen i s formed in th e purifier by theabsorpt ion of hydrocyan ic acid in presence Of oxygenand ammon ia

,and con sequen tly more thiocyanogen

is formed when air i s added to th e crude gas thanwhen such air is lacking . Moreover , th iocyanogen

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and an i l luminat ing gas . The ammonium salt isthen decomposed by passing th e mixture throughdilute sulphuric ac id ; and th e hydrocyan ic acid i sabsorbed by means Of caustic soda or potash .

Th e n ext Paten t dealing with the absorption Of

hydrocyan ic acid by the wet method is that of

Knublauch (Ger . Pat . This process isbased on th e absorption Of hydrocyan ic acid by a

liquid contain ing an iron sal t in solution ,toge ther

with alkalis and alkal ine earths . When thesesubstances ar e present in certain re lative proportions

,th e carbon dioxide and sulphuretted

hydrogen passing through along with th e gas ar e

absorbed to on ly a min imum exten t , and the

quan t ity of iron su lphide formed in th e Operat ionis in perfectly definite re lation to the potassiumferrocyanide and entirely independent of the carbondioxide and sulphuretted hydrogen traversing the

liquid . This mean s that,under certain condition s ,

i t is possible to absorb nearly th e whole of th ecyanogen

,without enriching the absorbent material

with carbon dioxide and sulphuretted hydrogen .

The Patent Specificat ion,which re lates to an

improved method Of . recovering cyanogen compounds , states that th e gases Obtained by th e drydisti llation Of coal

,coke

,brown coal

,bituminous

shale,peat or wood

,as al so blast-furnace gas , ar e

brought into intimate contact with a l iquid (wateror sal ine solution) contain ing one or more Of the

substances in group A (see below ) , together withone or more of those in group B ,

or e lse—given a


su"

Ciency Of ammonia in the gas—one or more of

th e group B substances .Group A. Alkalis , ammon ia (gas l iquor) , alkal ine

earths,magnesia and the carbonates of th e said

bases .Group B . I ron

,manganese and zinc

,as also the

native or artificially prepared oxides,hydroxides

,

and carbonates of these metal s .Th e proportions to be employed per molecule of

the cyanogen present in th e gas , ar e approximately1 molecule Of alkali

,alkaline earth (magnesia) or

the ir carbonates , with less than on e molecule Of th e

metal lic compounds mentioned under group B . I f

ores or metals be used , th e quantity should be increased in accordance with th eir lower activity

,the

amount of alkali,however

,be ing st ill approximately

1 molecule .

The Object Of this process was to absorb all thecyanogen in a soluble form but

,owing to the readiness

with wh ich iron oxidizes,this could not be e

“ °

ected

completely,smal l quant ities of Prussian Blue being

always found in the iron sulphide sludge . Th e

Knublauch process never made headway in p ractice ,

th e reason probably being that th e demand forcyanogen salts was then too small To thisinventor , however , belongs th e credit Of having , byhis careful researches

,pointed out th e way to

absorb cyanogen by the wet method . A few yearslater , W . Fou lis embodied a modification of th eprocess in his English Patent accordingto which the hydrocyanic acid is recovered

,in th e


form of potassium ferrocyanide,or th e correspond

ing sodium salt , by treating ammonia-free coal gaswith freshly prepared ferric carbonate

,he ld in

suspension in be l l scrubbers . This form Of scrubberwas afterwards replaced—in th e same inventor

’

sPatent —by scrubbers in which th e

charge was kept in motion by mechan ical devices ,an arrangemen t more suitable for s ludgy liquids .For carrying out th e process , 5 gal s . of a solutionof ferrous ch loride—contain ing about 15 lb . ofFe per gal lon—ar e treated wi th a solution Of 15 lb .

Of calcined soda in 30 gals . Of water . After stirring th e whole thorough ly

,the precipitate Of ferrous

carbonate i s al lowed to subside,the supernatan t

liquid be ing poured Off and th e deposit washed un ti lal l th e sodium chloride has been removed ; 2 7 lb .

Of cal cined soda,or 3 5 lb . Of potash

,ar e then added ,

the volume Of the suspension is made up to 40 gal s .

with water,

and the charge is placed in the

scrubber . A report Of th e result s Obtained with th eprocess , in practical use

,at the Hague gasworks

was published byRutten (“ Journa l O fGas L ighting ,

1902 ,vol . 80

,p . 8 79 ) who used ferrous su lphate

instead Of ferrous chloride,

and employed as ab

sorption vesse l a Kirkham scrubber,the first

chamber of which was Charged with heavy tar oilfor the purpose of retaining the naph thalene .

Whereas both Knublauch and Fou lis prescribed theremoval of ammon ia from th e gas before absorbingth e hydrocyan ic acid , the gas in th e Hague trial swas mere ly freed from tar before being passed


th rough th e absorbent Charge . When the firstchamber was found to be saturated with hydrocyanic acid

,it was emptied , and. th e liquid from the

second chamber was pumped into th e first one , thatfrom th e third into th e second , and so on

,th e

Operation be ing repeated as soon as the firstchamber became saturated again . The counterflowprinciple was thus Observed ; and i t was found thatth e absorption Of hydrocyan ic acid was pract ical lycomplete . I n the case Of a crude gas con taining ,on th e average , per 100 cubic cent imetres

°

H ydr ocyan ic acid 185 grams

Ammon ia 325

Car bon d iox ide 4000-6000

Sulphur etted hydr ogen 1500

8 5 per cent of ammonia and 3 7 -67 per cent ofcyanogen were found in the s ludge Of a slightlyoxidized preparation . Jor r issen and Rutten al sofound that

,in th e absence of carbon dioxide

,al l th e

cyanogen can be recovered in the soluble form,and

that th e presence Of ammonia does not lead to th eformation Of thiocyanate . I n this cyanogen sludge

,

th e cyanogen i s present as Prussian Blue and as

potass ium ferricyan ide . The fai lure Of Knublauch’

s

attempts to absorb the cyanogen merely as salts insoluble form is attributable to the presence Of carbondioxide , on which accoun t B ueb proceeded in such a

way as to prevent the formation Of soluble saltsentire ly , and to Obta in the cyanogen in the sludgeonly , wh ereas in th e previous methods both th e

s ludge and the solution required to be treated for


the preparation of cyanogen’

salts . B ueb’

s process

(Ger . Pat . 1124 5 9 ) is worked with a solution ofiron salts

,of such high concen tration that no ab

sorption of ammonia takes place,and the amount of

iron is very large in proportion to the ammonia .

Th e hydrocyanic acid is thrown down as insolubleammonium ferrocyanide . Th e absorbent liquid i sprepared from a coldsaturated solution of ferroussulphate

,containing about 280 grams of sulphate

per litre and th e apparatus consists of a horizon talcylinder the l iquid contents of which ar e kept inmotion by mechan ical stirrers . This cylinder is setup between the tar separator and the ammoniascrubbers

,and con sists of severa l chambers

,th e first

two of which ar e used for absorbing naphthalene bymeans of a charge of heavy tar oil containing up toabout 8 per cen t of benzol The next fourchambers ar e fi lled one - third ful l with the coldsaturated solution of ferrous sulphate . I n order topresen t a maximum wetting surface to the gas , a

shaft passing horizontal ly through the cylinder isprovided with wood faggots in the . naph thalenechambers and sheet metal disc s in the cyanogenabsorption chambers . The shaft i s set in rotationby a worm and worm-whee l gear . Th e gas passesfirst of al l through the chambers charged withheavy tar oil , where the naphthalene i s retained '

and from these it enters the cyanogen absorptionchambers . The scrubbing liquid does not flowthrough these chambers continuously , but is station

ary . After th e liquid in th e first chamber is


complete ly saturated with hydrocyan ic acid—whichtake s about nine hours in large plants—it i s run out ,the liquid from the second chamber be ing pumpedin in it s place

,whilst th e liqu id in each of the other

chambers is advanced a stage,and the final cham

ber i s recharged with fre sh liquid The me thod ofworking is th erefore exactly th e same as in the

Fou l is process . The absorption of th e cyanogen i sbased on the following reactions .

Th e ammon ia decompose s the sulphate intohydroxide

,sulph ate of ammonia be ing formed :

( 1 ) Feso, QNH32H 2O Fe (OH ) 2 (N I

-102804

Su lphuretted hydrogen acts on th e hvdroxide ,

ferro i s sulphide being formed

(2 ) Fe (OH )2 1128 FeS 211

20 .

I n presence of ammon ia’

and hydrocyan i c acid,

the fe rrous sulphide is converted into ferrous cyan ide ,

ammon ium ferricyan ide being al so formed .

(3 ) Fes QNH3

QH CN Pe (CN ) (NH 4 ) 2S .

(4 ) QFeS GNH,

GH CN

Both th ese cyanogen compounds ar e insolublein water and ar e precipitated as s ludge . I f, however , they ar e al lowed to remain in prolonged contact with th e l iquid

,they ar e gradual ly converted ,

by the further action of hydrocyanic acid,in to

soluble ammon ium ferrocyan ide,according to th e

equations


( 5 ) Fe (CN ) 2 4H CN 4NH (NH Fe (CN ) G

and

(6) 6NH 3 GH CN

As i s evident from these reaction s,the B ueb

process al so furn i shes smal l quantities of cyanogenin a soluble form in practice . The sludge obtain edis dark brown to black in colour and contain s an

amount of cyanogen equivalen t to 18 -20 per cen tof potassium ferrocyan ide” According to the r e

searches of Hand, Ost , and Kir ch ten ,

the in solublesalt has th e formula : Th e

ammon ia present in th e sludge i s partly combinedwith iron cyanide and partly as sulphate

,and

amoun ts to about 5 - 7 per cent . Owing to th e impossibility of en tirely exclud ing oxygen

,a smal l

quantity of th iocyanate i s also formed,according to

th e equation :

ZNH3

21128 0 (NH 4)2S 11

20 + S .

(NH 4) ,S S (NH 4Q2S2

(NH , ) 2S2 NH3

H ON (NHQCNS (NH 4) 2S .

The free sulph ur is deposited from the ferroussulphide and water in presence of air . Fe ld hasconfirmed that th e formation of thiocyanate takesplace chiefly in

_th e chamber nearest to th e gas

outlet , and that there is very l ittle further increasewhen th e l iquid is transferred to th e penultimatechamber .

A combined system of cyanogen absorption,anal



absorbed by a hot solution of bas ic magnesium salt .Th e cyanogen i s n ext absorbed in a cold

,neutral or

bas ic carbonate solution ,or by hydroxide s or oxides

of magnesium,zinc

,aluminium

,manganese or lead

,

the hydrocyanic acid be ing liberated from the solution by distillat ion

,and absorbed in the form of any

cyan ide . No practical experience with this processi s at presen t avai lable .

The last meth od of cyanide absorption by th ewet process that need be m en t ioned con sists inconverting it in to thiocyanogen . However

,since

th e th iocyanogen compounds ar e far less valuablethan those of cyanogen

,this method is of interes t

on ly to gasworks which have to deal with coals v eryhigh in sulphur

,for which reason it has found ap

plicat ion in some English gasworks . I t i s basedon th e conversion of the cyanogen into thiocyanogenby mean s of polysulphides in presence of ammonia .

With this obj ect the gas i s washed with an aqueoussuspension of flowers of su lphur ( 10 per cent byweight ) . The following reaction s take place :

4. s (NH QQSQ .

(NH4)282 NH

,H ON NH

4CNS

Up to 90 per cent of th e cyanogen is absorbedas thiocyanogen ; but the presence of large quantities of carbon dioxide i s said to have an adverseeffect . Paten ts for processes of this kind have beentaken out by : Smith , Gidde , Salomon and Albright

(Eng. Pat . Carpen ter (Eng. Pat .

and th e British Cyanides Co . Lim .

(Ger . Pat .


An attempt has been made in th e foregoing , togive an idea of th e mann er and the chemical condit ion in which the originat ing material s for th eby

-products of gas -making ar e obtained . Theseby_products ar e : coke

,retort graphite

, ammonia ,

sulphate of ammon ia,sulphur

,ferrocyanic acid and

thiocyani c ac id .

CHAPTER I I .

COKE.

COKE i s th e first product obtained in th e retorts as

th e distillation residue from coal . I n large gasworks

, the retorts ar e emptied by mechanical ap

pliances , and th e glowing coke i s removed by be ltconveyers

,which pass through water in order to

quench same . I n smal l works it i s whee led in

barrows to a large heap where the quenching isperformed .

Gas coke forms a porous mass , ranging from silvergrey to a dark colour . I t i s very brittle and hard .

I ts chemical composition has not yet been identified .

I t does not,however

,form ‘

a mixture of pure car

bon and'

ash constituents—th e non -volatile minera lconstituen ts of th e coal—but is a mixture ofhigh-molecular compounds of carbon with hydrogen

,

ni trogen,oxygen and sulphur . Apart from the ash

,

th e composition natural ly differs according to thekind of coal ; and it al so depends on the cokingtemperature employed

,th e proportion of carbon in

creasing with the temperature . The porosity depends on the meth od of disti llation , that is to say ,

on the position of th e retorts . Thus,as a rule

(22)

COKE 23

vertical retorts furn ish th e den sest coke , because inthese i t s inters together more , under the influenceof its own we ight . Th e range of percentage of th evarious con stituents of gas coke , referred to dry and

ash -free matter,ar e as fol lows :

Car bonH ydr ogenOxygenN itr ogen

Su lphu rH eating value

The ash content fluctuates considerably,

and

ranges be tween 8 -7 2 and 11 -60 per cen t . The

above figures ar e taken from a Table compiled byBun te from samples of coke from the gasworks of

B erlin,Hamburg

,Breslau and Mun ich

,in 189 7 .

Th e examinat ion of coke i s d irected to its fragility

,th e determination of the volatile constituen ts ,

sulphur , ash ,and

,above al l

,th e heating value .

The test for ascertain ing th e fragili ty of coke isapplied in th e fol lowing manner : One port ion of th esample 18 separated by sift ing , and th e remaind eris dropped from a certain height on to a paved floor

,

and then sifted again . Th e amoun t of the screenings gives an idea of th e fragil ity of the coke .

Th e determination of th e ash,volatilematters and

sulphur need not be gone into here,since i t does not

present any special features .

The heating value may be determined by mean sof empirical formulae or by accurate experimen talexamination . Dulong ascertain s th e heat ing value

per cen t.

7708 -8022 cal .


from the chemical composition by means of th eformula

H 8 10 290 (H 1was cw .

in which H represents th e heating value in calories

per kilogram ; C is th e percentage of carbon inth e substance ; H 1

the percentage of hydrogen ; C

the percentage of oxygen ,S that of sulphur

,and W

the percentage of moisture presen t , both originallyand as produced by the combustion of th e sample .

Th e recognized method of determin ing heat ingvalues i s by means of the calorimeter , which is a

stee l bomb fi l led with oxygen under pressure .

Th e substance under examination is powdered , andcompressed into a tablet

,in which an iron wire , of

known carbon con tent,or one of platinum ,

i s em

bedded at th e same time . This wire i s rai sed toincandescence by th e aid of an e lectric current

,and

thus ignites the tablet which has been placed inside th e bomb . The heat thus liberated i s tran smitted to water in which th e bomb is immersed :and th e rise in th e temperature of th e water formsa measure of th e heat ing value of th e substance .

Th e water is kept in con stan t motion to ensure a

uniform distribution of the heat and the whole ap

paratus i s placed in a second vesse l containing water ,in order to protect it from th e influence of externa lheat . However

,s ince th e heat i s tran smitted to al l

parts of th e apparatus and not mere ly to th e wateralone ,

it is necessary to take in to consideration th e“ water value , as regards heat , of such parts . I f

COKE 25

th e water value of th e vessel be taken as X,and the

we ighed quantity of water be represented by Y,the

correction for radiation—according to th e formula ofOstwald—be ing set down as Z ,

th e in itial watertemperature as T

Iand th e maximum temperature of

th e water during the experiment as T2, then the

heating value,expressed as heat units (calories ) , will

be : Cal Y (X Y) (T2 TI

Z1) . From this

result there must be deducted th e heat generatedby the iron wire and th e n itrogen ; and since the

heating value i s referred to 1 kilo . of substance , th isvalue must be recalculated accordingly . Moreover

,

th e evaporation value of the water of combustionmust be deducted , for which purpose th e quan t ityof th e water of combustion must be determinedwhich can be e

° °

ected in the same experimen t , thebomb be ing con structed in such a way that th e contents can be complete ly emptied out and collectedafter the combust ion process . The water producedi s retained by a calcium chloride tube

,and th e carbon

dioxide by a potash apparatus arranged in successionto said tube . With th is object th e bomb is heated to105 -110

°

C . ,and

,after the pressure has become

equalized,dried air is passed through it for a short

time . The increase in weight of th e calcium chloridetube gives the weight of the water of combustionformed and for every kilogram of water of combustion

,606-6 cal . must be deducted from th e heating

value found by the formula .

The coke coming from the retorts is not homo

geneous in character , and is in lumps of di'"

er ent

26 COAL GAS :

BY-PRODUCTS

sizes . I n order to obtain a product of un iform ap

pear ance , th e large lumps ar e broken ,e ither by hand

or,more generally , in coke-breaking machines after

the style of that illustrated in Fig.1 . This machine

cons ists of a shaft provided with interchangeableteeth or cutters to wh ich the coke i s fed down an

inclined plate,which al so forms anabutment . Th e

broken coke is passed over mechan ically Operatedscreens of di er ent mesh , and i s thus classified at

once in to various sizes . The coke xfines ( fragments be low {p inch diameter ) can be worked up ina briquetting machine

,

The ash from th e fue l used in heat ing the re tortsalso con tains unconsumed par ticles of coke

,which can

be separated by hand , and con stitute the so-calledcoke breeze

,which forms an inferior

,cheap

grade of coke,of about one - th ird th e value of gas

coke .

There i s no need to dilate upon th e u se of coke asa heating agent

,but a good deal i s con sumed by the

gasworks themselves as fue l , particularly for charging th e producers ,I n th e gasworks of large towns the consumption of

gas varie s considerably at different times of the day ,

but increases very quickly at short in terval s towardsevening

,and th is increased consumption cannot be

met at once by the retorts alone . I t may , however ,be dealt with quickly by mixing th e coal gas withwater gas , the output of which can be regulated moreeasily

,Another important factor in the case of water

gas i s th e amount of floor space required , it being


28 COAL GAS B Y-PRODUCTS

Water gas i s made by pass ing steam throughglowing coke ; but though the process dates backabout a century

,i t is only within th e last few de

cades that a usable product has been obtainable .

I f th e charge of coke be heated to about 500°

C . ,

hydrogen and carbon dioxide ar e formed when th e

steam is blown in whereas if the temperature of

th e coke be raised above 1000°

C . ,th e carbon dioxide

formed is reduced .to monoxide in passing through

th e upper layers of glowing coke . The re ar e, con se

quen tly,two processes for making water gas ; the

carbon monoxide process,which furn ishes a fue l gas ,

and the carbon dioxide process .

Thus , at 500°

C . ,the reaction i s

C 2HZO = 2H

2CO

Whilst at 1000° C . it i s :

C + CC 22H

22CC 2H

2.

I n practice th e proces s is carried out on the following general l ines . Coke i s ignited in a retort and

raised to incandescence by means of a bottom blast .Th e air i s then shut off

,and steam is forced through

th e glowing coke,by which it i s decomposed in to

hydrogen and oxygen . So soon as the temperatureagain fal l s below or the coke i s raisedto incandescence once more by restarting the blast .These two Operat ions ar e known respectively as

blowing and gas ifyingSchafer gives the fo l lowing as the percen tage (by

volume ) of a water gas

COKE 29

Hydr ogenCar bon monox ideCar bon d ioxi deN itr ogenOxygen

Th e heat of combustion o f such a water gas

amounts to about 2500 ca l . and its h eating value isabout 12 per cent lower than that of coal gas .

CHAPTER in“

.

RETORT GRAPH I TE.

RETORT graphite or retort residue is formed by thedecomposition of the hydrocarbons produced in th edistil lation of coal in the retorts , a portion of the

gases being decomposed into the ir constituent e le

ments by the h igh temperature . The carbon formedin this way is al so deposited on the fir ebr ick wal ls ,and furn i shes a hard mass which resemble s graphiteand will even give out sparks when struck by a pieceof stee l . This graphite i s a very bad conductor ofheat

,and therefore has to be taken out of the retorts at

interval s of four or fiv e months . The thickness Of thedeposit is somet ime s considerable ,

that from Englishcoals be ing not infrequently 25 3 ins . th ick The

mass is cleared away ei ther by purely mechanicalmeans or by burning

,the latter being generally pr e

ferred,because th e extreme hardness of th e deposit

renders the material Of the retorts l iable to in jurywhen mechan ical means ar e employed . To burnout the graphite

,half-moon bricks ar e placed in the

hot,empty retorts

,so as to form troughs , the open

ings in which ar e closed,together with the retort

heads,whilst the cap of the upcast pipe i s Opened .

(30)

RETORT GRAPH I TE 31

The air flowing through the retorts then burns thedeposit and loosens its hold on the walls , which

Operation takes from four to sixteen hours . When

cold th e loosened graphite can be completely removedby mechan ical means .The specific gravity of retort graphite varies be

tween 1 -7 2 and 2 8 5 according to the pressur ewhich has prevailed in the retorts . Th e degree ofhardness also varies considerably . The ash conten t

“

i s about 2 -5 per cen t .Bunsen proposed to u se retort graphite for carbon

e lectrodes for e lectrical purposes,and thus opened

up a large market for the article . I n fact practica lly al l carbon e lectrodes and rods ar e made of

'

r etor t

graphite . The r aw material,however

,is not per

fectly homogeneous , and the shape of th e retorts isadverse to the production of any but comparativelysmal l plates and rods . On this account

,and because

the direct treatmen t of the r aw material would giverise to a good deal of waste

,the crude graphite i s

first hand-picked and cleaned,and i s then ground

down to a coarse powder . This is next worked upinto a plastic mass

,along with lampblack and coal

tar,in a mixer , and from this mass the carbon rods

ar e shaped in hydraulic presses under a pressur e ofseveral hundred atmospheres

, th e plate s being treatedin a similar manner . Th e re sulting mass

,however

,

has not yet attained its ful l strength ,which is im

parted by baking in c ircular kiln s similar to those usedin brickmaking

,The heat of the kiln decomposes the

coal tar,and the result ing graph it i c carbon binds


the grain s of th e retort graphite toge ther . Th e

product is used for th e carbon rods of ar c lamps ,chiefly on account of its very low combustibil ity ,

Most of the works engaged in the manu facture ofe lectric carbon s ar e situated in th e district roundNuremberg

,though the largest firm

,Gebr . Siemen s

Co .,i s in Berlin .

CHAPTER IV

GAS TAR .

THE third product met with between th e re tort andthe gas holder and h aving to be extracted from the

gas , i s tar . This tar i s deposited in three chiefplaces the hydraulic main ,

th e air condenser and thewater-cooled condenser , a portion of the gas l iquoral so separating out at th e same time . On thisaccoun t

,the gas tar and gas l iquor , together with

that from th e scrubbers,ar e col lected in one pit

,

Where their difler ent den s ity causes them to separate in to two layers , the specifical ly heavier tar

being at th e bottom . By mean s of a siphon,which

reaches down to th e bottom of th e pit,th e tar i s

drawn 0 from th e supernatan t l iquor and i s thenpumped up into a h igh leve l tank .

A full description of the treatment of this tar i sbeyond th e scope of th e presen t work and i t needon ly be men tioned that th e entire dyestu industryemploys gas tar as th e r aw material for the preparat ionof al l th e crude products of that industry . Al l thatwill be dealt with here i s th e direct utilization of the

crude tar,and i t s f ractional d ist il lation in to light ,

medium and heavy oil s , anthracene Oil and pitch .

(38) 3


The yield of tar Obtained in gasworks depends onth e origin and character of th e coal , and ranges (seeTable be low ) between 4 and 8 per cent , coals rich inoxygen usually furnishing th e highest tar output .Th e following data were compiled by Bun te as the

result of a large number of experiments :

O rigin of Coa l . Retor t Temperatur e .

Per centage Of Per centage OfTar . Gas Liquor .

Wesphalia 1360

Saar di str ict 1205-12900C .

B oh emia 1240-1350°C .

Zwickau 1180-1240°C .

B oh em ian cannel 1180-1850°C .

Gas tar i s.

a thick,deep-black greasy liquid

,but is

not a homogeneous substance,being a mixture of

highly divergen t hydrocarbon compounds . I n ad

dition to water it contains hydrocarbons of themethan e , e thylene and acetylene series ; naph thy

lenes ; terpenes ; naphthenes ; aromatic hydr ocarbons of th e benzol

,naphthalene and an thracene

homologue series ; phenols ; aromatic acids and

sulphur compounds ; bas ic and non-basic aromaticnitro -compounds and free carbon .

Kr amer h as found samples of German gas tar tocontain

B enzol and its homologues , Cnq 6 per cent .

Phenol and its homo logues , Ca n 70151Pyr idin and ch inol in bases

, Ca n 7N

Niphthal ene, CnH 2n 12 03 )



Temperatur e . From Ve r t ical Retor ts . From Slant ingRetor ts .

per cent per cent

O-100°C . 8 8 of oil , 5 7 of water 1 O of oil

, 08 5 of water

100-170°C . 1 °2

170-230°C . 13 5

230-270°C . 7 3 7 5

Over 270° C . 29 3

Res i due 34 °1 58 13

According to th e use for which it i s intended,the

tar is examined for water con ten t,percentage of

ash ,heating value

,specific gravity and carbon con

tent . Gas tar itself i s not a homogeneous substance ,

a Whole series of bodies separating out , in accordance with their specific gravity , especially on prolonged standing .

For this reason , it is essential to employ greatcare in obtaining a good average sample for thepurpose of judging the value of a tar . The bestmethod of sampling is to mix the tar in the vesse lby blowing air through it , and then taking samplesfrom different

places . Ahrens and Senger r ecom

mend , as an e cien t tar sampl ing device , a tubewhich is long enough to reach to th e bottom of th etar vessel , and i s traversed by a rod provided on itslower end with a con ical or flat valve member

,so

that th e sampler can be closed by a pul l on the rod .

I n taking samples , the tube ,in th e Open condition

,

i s worked slowly down as far as the bottom of th evesse l

,and i s then closed at its lower end by pull ing

on the rod . I n this way a complete sample of theseveral layers of tar in th e ve ssel i s obtained . By

GAS TAR 37

repeating the Operation in differen t parts of thevesse l an average sample i s Obtained .

For determining the percentage of water , Mai

wald recommends dist illing 100 grms . of th e tar in

a copper still,capable of holding 200 grms . and con

nected to a L iebig conden ser,50 grms . of benzol

being added to th e tar to prevent i t from frothing upand boiling over

,By the time the stil l temperature

attains 190°

C . al l th e water wil l have passed over .

The disti llate i s collected in a measuring cylinder ,in which th e layer of oil separates from th e water , sothat the percentage amoun t of the latter can be readoff direct . Merchantable tar should not containmore than 4 per cent of water ; and if found tohave more than this amount , an al lowance should beclaimed on account of th e unnecessari ly increasedcost of carriage .

According to Senger,500 grms . should be -dist illed

in a 1 l itre copper still,without addit ion of benzol , the

frothing of the tar being prevented by the application of heat from above

,by means of a ring burner

arranged under th e upper rim of th e still . Con

ducted in this way th e operation requires no supervis ion , and is completed in about three or four hours .I n the Maiwald method th e disti llation is finished inhalf an hour .Th e heating value i s determin ed by mean s of

the Berthe lot bomb,in th e same way as for coal .

According to Al lner,i t i s advisable to soak th e tar

up in cel lulose cubes,in order to obtain comple te

combustion of th e carbon , the heat of combustion of


the added material be ing de termined beforehand and

deducted f1om the result furn ished by the calculation . Berte l smann

,however

,has found no di culty

in effecting th e direct combustion of the tar .

Th e specific gravity is determin ed by the methodof Lunge . A smal l we ighing glass i s used as

pyknometer,and a notch

,about 2 mm . wide and of

th e same depth,i s fi led in th e edge . Th e fol lowing

Weighings have to be performedThe tare weight of th e vesse l a

Th e we ight of the vessel fi lled with water at 1 5 °

C . b ;

The weight of th e ves se l fi l led about two- thirdsfull of tar 0

The weight of the vesse l now fi l led up complete lywith water d .

c —a

b + c

Before making this determination,i t i s necessary ,

of course,that th e tar sh ould be freed from water .

This can be effec ted by leaving th e tar to stand ina covered glass beaker for about twenty -four hoursat 40

°

C . ,under which condi tion s th e tar and

' waterseparate from each other . The supernatan t wateris then poured ofl

,the final traces being soaked up

with fi lter paper .

I n determin ing th e value of c , the vesse l shouldbe al lowed to stand in hot water for some considerable t ime

,to expel al l air bubbles from th e tar .

For determin ing the carbon con tent , Kohler pr e

Then

GAS TAR 39

scribes heating 10 grms . of th e tar with a mixture of25 grms . each Of glacial acet ic acid and toluol forsome time

,and then passing the whole through a

tared fi lter,the residue being washed with benz ol

until th e washings ar e free from colouring matter .

Th e carbon rema ins on th e fi lter and i s determinedbyw eighing .

Kramer and Spilker warm 1 part of tar with 3 ofan iline

,and pour the mixture on to a plate of unglazed

earthenware,wh ich absorbs the l iquid constituents of

the tar . The residual carbon is then tran sferred toa tared watch glass by means of a spatula and

weighed .

For the determination of th e various fractions intar

,Kramer and Spilker recommend a method

adopted directly from practical working on the largescale

,5 kilos . of the tar under examination being

placed in a cast-iron stil l,holding about 8 kilos

,and

dist illed in a partia l vacuum,the fractions being

col lected at defin ite intervals of time .

Th e ash conten t i s ascertained by warming 1 grm .

of tar in a platinum dish,then ign iting it , and when

the flame has subsided,heating th e residue in a

mu e until of constant weight . Th e ash se ldomexceeds about 00 5 grm .

As already mentioned, th e tar collected in th e tar

tanks sti ll contains a large amount of water,from which

it must be separated . According to th e method Of theDeutsche Con tinen tal Gas Gesel lschaft (Ger . Pat .

th e mixed tar and water is allowedto flow down an incline of 4 5 °

in a th in stra tum .

40 COAL GAS BY PRODUCTS

During th i s operation the tar and water separate ,th e tar col lecting in a pit at the bottom of th e slope ,whilst the water floats on th e surface . Schlosser

’ star separator is based on the same principle , the tar

being al l owed to flow over the edge of a high_ leveltank on t o a vertical corrugated plate

,below which

is a collecting tank in which the tar and water formseparate strata .

Anoth er method,frequently employed in large

gasworks and tar disti lleries,’

consists in th e application of centrifugal for ce l Burmei ster and Wainproposed to u se a centrifugal tar separator constructed on the same principle as th e milk separator .The drum is run at a speed of about 2000 r evolu

tions per minute ,and th e tar

,which i s fed into it as

a continuous stream,at a temperature of about 30

40° C . (86-104 ° F . ) separates from the water , whichrises to the top

,ins ide the tar , and i s retained in the

central space of th e drum by a partition,over which

the tar flows outward , the two liquid s being thusforced apart .One very simple method con sis ts in merely warm

ing the tar , in which case the temperature should notexceed 50°

C . ( 122° order to preven t l oss . I n

thi s state of increased fluidity a separation of the tarand water takes p lace automatically .

According to KlOnne (Ger . Pat .

tar can be freed from water by forcing it betweenrollers

,which ar e heated if necessary

,th i s treatment

freeing the imprisoned par ticles of water from the

adherent tar by pressure and friction .

GAS TAR 41

The Weil method (Ger . Pat . 21 7 65 9 and 218 7 80/1908 ) is performed in a partial vacuum . Th e tar

flows,as a continuous current , round a system of

pipes heated by waste gases . To prevent loss ofreadily volati le constituents , a condenser and washerfor the ir absorption ar e arranged in th e rear of the

vacuum pump .

I n a large number of systems th e device for r e

moving the water from the tar i s placed in directconnection with th e distil lation apparatus . A methodof this kind is that patented by the Rutger swerk e

A . G . (Ger . Pat . in which , by th eapplication of heat from above downwards , the floating water is got rid of first , th en that emulsified withthe tar

,and final ly th e chemically combined water .

Th e flue gases from the retorts ar e utilized as th e

heating agen t .The crude tar Obtained in th is way is used for

paint ing cast- iron articles,for making lampblack and

for r oofing-fel t . For applicat ion to metal surfaces

the tar i s made fluid by h eat,and then laid on th e

metal d irect,producing a lustrous and durable black

coating . This paint i s used on cas t- iron pipes intended to be exposed to corrosive vapours

,for ex

ample in chemical works . Kuhlmann also r ecom

mends gas tar as an acid -resisting pain t for stoneand brickwork ; but i t is not much used as a preservative for wood . One Of the mo st importan t directapplications of gas tar i s in the manufacture of roofing fel t . This is a very simple process , the millboard or fe lt be ing boiled in water-free tar or passed


continuously through hot tar solutions,whilst th e

surplus tar i s removed by pre ssing the material between rollers . I t is more economical to carry onthe work in closed cylinders

,instead of open pans ,

in order that the readily volatile constituents may be .

recovered by condensation . The crude tar may al sobe replaced by a mixture of tar pitch and heavy Oil

,

in which case th e roofing fe lt wi l l have to be fr e

quen tly recoated with th e same preparation duringthe first few years it is in u se .

Crude gas tar i s al so used for making lampblackbut a better product can be obta ined from the heavyOil . Of late years , tar has al so found advantageousemploymen t for dressing the surface of highways , inorder to render th em dustless and more durable .

Crude tar,from which the constituents boiling up

to 150°

C . have been distilled is made into artificial stone (B orrite stone ) with dried and crushedgravel

,furnishing a product characterized by great

hardness and strength .

The possibili ty of producing an il luminating gasby passing coal tar through r ed -hot pipes has not

found any practical applicat ion ; but , on the otherhand

,this tar is uti l ized as fuel

,h aving a heating

value of about 8 5 00 cal . Th e tar flows through a

nozzle to the burner and i s forced in to the combu s

tion chamber by a mixture of steam and air .

As already men tioned in the introductory chapter ,

gas tar is l ikewise used for absorbing gases ; and i t‘

also serve s to absorb naph thalene in naph thalene

and cyanogen washers .


44 COAL GAS BY—PRODUCTS

product,th e heavy oil

,comes over up to 300°

C . ,

and,in addition to naphthalene

,consis ts main ly of

creosote Oi ls . Anthracene oil , th e final distil late,

comes over at temperatures up to 400°

C . ,and

contains crude an thracene,which is solid at the

ordinary temperature . Th e fi ltrate from th i s deposit i s redistil led and furnishes an additionalquantity of crude anthracene , together with carbol ineum

,which latter is used as a preservative for

timber . Th e pitch formmg th e residue in the sti l l ,i s a product of varying consistence and i s composedof carbon compounds of unknown composition

,

mixed with carbon .

Th e apparatus used for tar dist il l ing varies consider ably in appearance

,but not greatly in principle .

A distinction may be drawn between three mainsystems of disti llation with direct fi r e heat or flu egases ; with indirect steam ; and vacuum distillation . Recently

,continuous dist illation has al so

come into favour .The water-free tar i s disti l led in iron stills , pr e

fer ably of wrought iron , which material i s moreeasily workable than cast iron and i s al so able towithstand greater fluctuations of temperature . The

more general u se of cast iron is , moreover , precludedowing to the narrow limits of size possible with thismaterial ; though wrought iron is more liable tosuffer from the heat . I n order to protect th e stillfrom direct contact with the heating flame

,a pro

tective casing is provided under the s ti l l bottom,so

that on ly th e hot gase s come in contact with th e

GAS TAR 45

apparatus , which is , therefore , to some extent,in a

kind of air bath . The flues must be arranged insuch a manner that

,during the whole of the dis

til lation process , down to the pitch—which , i t istrue

,occupies about two -thirds the total volume of

the tan—th e heating gases only come in contactwith those parts of the sti l l which ar e fi lled withliquid .

Tar st i lls d iffer considerably in shape , bothvertical cyl inders

,as high as they ar e wide ,

and

horizontal cyl inders,being used . I n th e case of

upright cylinders th e bottom is domed (con cave)and th e upper end i s of similar shape

,this latter

being provided with an outlet for the liberatedgases . Th e

'

reason for using a domed bottom in

stead of aflat one i s that th e former is able to givebetter

’

under the influence of th e high and consider ably fluctuating temperature , whereas a flatbottom would soon get out of shape and make the

complete removal of th e pitch from th e still a

di" '

icu lt matter . Very often th e sti ll i s made inone piece

,inwhich case th e dome at th e top is pro

vided with a manhole for charging and clean ing outthe stil l . I n another form Of still the whole domeis detachable

,and the flanged joint s have to be r e

packed every time a fresh charged is distil led . Th e

best packing material i s asbestos . I n th e case ofhorizontal st il ls

,th e quest ion of distortion does not

h ave to be con sidered . A cock for drawing off th e

pitch is provided at th e deepest point of th e sti ll ,which is usual ly set on the brickwork so "’

as to have

46 COAL GAS BY PRODUCTS

a slight tilt . I nternal ly , th e still i s provided withstirring mechanism—adapted to th e shape of th e

sti ll— in order to facilitate uniform heating of thel iquid

,and also to prevent the charge burning on to

the stil l wal ls ; but these stirrers ar e not set towork un ti l th e higher distillation temperatures ar e

reached and th e residual charge has become verythick . A better method of keeping th e charge inmotion is by blowing in dry

,superheated steam ,

because this facil itates d ist illation at th e same time .

I n place of vertical stills , th e horizontal pattern isused

, especial ly in Scotland,the cylinders being

about 21 ft . in length and 8 ft . in diameter . The

stil l i s protected from direct contact with th e fir e

by an arch,th e flame passing through about twen ty

open ings in th e side s into flues which surround th ecylinder up to about its middle l ine . The stirrin gmechanism used consi sts of a shaft carrying horizontal r ods , on th e ends of which ar e attached sh ortchain s which scrape along th e bottom of th e still

,

in alternate posit ions,so that one chain scrapes

along a part which has been left un touched by thepreceding one . I n large works a stil l charge isabout 20 ton s

,but in smal ler works

,12 tcn st il ls

ar e used . Though th e larger s izes ar e th e moreeconomical in working

,it i s not desirable to go above

a capacity of 18 22 tons,s ince th i s quantity can be

finished o in about twe lve to fourteen hours,whereas

larger charges require n ight sh ifts . Th e heavy oi land anthracene oil ar e mostly disti lled by the aid ofsteam and a partial vacuum .

GAS TAR 47

I n al l the foregoing sti ll s th e tar must first befreed from water before distilling ; but latterlymethods have arisen in which the heat producedduring distillat ion i s utilized for removing th e waterfrom the crude tar at th e same t ime . Thus ,ReSpier drys th e tar in a column stil l

,of exactly

the same type as that for disti lling ammonia l iquorand mounted on th e cover of th e dehydrating

retort . Th e tar is r un into th e column through an

intermediate member s ituated between th e threelower and th e two upper chambers . The gaseousdist illates

,water and light oil issue through a pipe

connection mounted on th e cover , and pass away toa condenser . I n addition to this continuous . dehy

dr ating retort , ar e three stills for the separation ofmedium ,

heavy and anthracene oil respectively .

Th e method of working is as follows : I n startingOperat ions , crude tar i s slowly heated to about200

°

C . in th e dehydrating retort ; and th e disen

gaged gases flow th rough th e column . Crude tar

enters through a lateral pipe and i s heated by th eexhaust gases so that the bulk of i ts contained waterand light Oil ar e expel led , this tar then pass ing in toth e retort

,where th e final traces of this fraction

ar e distilled o”

. Th e dehydrated tar i s drawn O

at a rate corresponding to th e rate of feed,into a

storage tank,whence it i s passed into one of the

other retorts,for fractional distil lation into medium

,

heavy and anthracene Oil . Th e d ist illation of thesefraction s i s carried on in cacao

,and proceeds in a

very simple and rapid manner . Th e dehydrating


retort dries su"°

cient tar daily for two or three 18ton stil ls

,and the whole Operation i s performed in

about ten to twe lve hours,

I n another method,according to Rispler , th e gases

issuing from th e stil l ar e cooled by crude tar,the

heat thus transferred serving at the same t ime tofree the crude tar from water and l ight oil . The

apparatus is arranged in th e fol lowing manner : A

complete ly closed , rectangular iron tank is fitted upwith a coil , composed of straight pipes with shortbends , which coi l i s traversed by th e sti l l gases .Over this coil is a pipe ben t to th e same shape

,but

perforated ; and through th is pipe the crude tar flowsin a thin stream on to the heated coil

,and parts

with its water and l ight oil , which escape to the con

denser through a connection in th e cover of th e tank .

The dehydrated tar , on the other hand,collects in

th e bottom and run s 0 through a connection to thesti ll . Th e mouth of this outlet i s closed by a be l lseal , to preven t any vapours be ing carried along by

the tar . The medium and heavy Oi ls ar e distil led by

fir e heat : but in distill ing O th e an thracene oil, a

partial vacuum is used , and superheated steam isforced through th e mass .Th e prevention of the risk of fi r e in tar distilling

is th e subject of a process paten ted by Opitz and

Klotz (Ger . Pat . in which superheated water is employed as heat tran smitter . An

endles s coil is arranged so that one portion i s situ

ated in a heating stove and th e remainder inside th es till . The hot water ascends through the coil , gives

GAS TAR 49

up its heat in the s til l and flows back , in a cooledstate ,

to the heater . Un less the heater is underneath the stil l a pump has to be connected up withthe coil so as to keep th e water in proper circulationand util i ze i ts heat effectually , For complete distillation it i s necessary that the water should be

rai sed to a temperature of 400°

C .

,a result which

i s poss ible of attainment , s ince,by increasing th e

pressure,the crit ical temperature of water can be

raised without converting it in to steam . With th isobject th e coil , which is made of special s tee l tubing ,must be tested to stand a pressure of 1000 atmospheres and by this means th e water can be heatedto 400

°

C .

,which is sufficien tly high for the distilla

tion of al l th e tar fraction s . By provid ing sui tablegauges and safety appliances , any desired temperatureup to th e above maximum can be produced and

automatically main tained . I n consequence of th eadvantageous manner in which th e tran sferen ce ofheat i s accomplished , this process i s economical inoperation ; and by th e separation of th e h eatingch amber from th e disti llation chamber th e risk offir e i s considerably lessened .

For the last stage of d isti l lation ,th e recovery of

creosote Oil , a vacuum (up to 1 5 mm . mercury gauge )i s used with great succes s . At th e same time

,steam

is introduced into the still,to preven t th e conten ts

from burn ing on to th e walls . The emp loyment ofth e vacuum makes th e process work more regularly

,

and ,in particular

,prevents obstruction Of th e con

den ser .


Continuous fractional distillation ,in vacu o ,

has

been considerably improved by Krey , who arrangestwo rece ivers behind the condenser

,with in terposi

tion of a bulb provided with a th ree-way cock and

air -tight be l l seal with gauge glasses . Both receiversar e connected to th e air -pump

,and ar e also provided

wi th gauge glasse s to enable th e progress of th e distil lation to be observed . Di stillation is conductedwithout vacuum until th e creosote oil stage i s reached .

By setting th e three-way co’

ck accordingly,th e frac

tions can be collected separately . After each fractionhas been collected , th e receiver must , of course , beemptied into a vesse l underneath . When the

vacuum is employed,th e two rece ivers must be

brought to the same pressure before revers ing thecock—a result which can be con trolled by means ofthe pressure gauge .

Of late years con t inuous distil lation has °madegreat progress . I n th i s system

,a continuous supply

of fresh tar i s in troduced and th e corresponding

quantitv of pitch is removed . Numerous proposal shave been made in this connection .

H irzel (Ger . Pat . uses a columnstill of similar pattern to that employed in di stil l ingammon ia . The various cel ls ar e heated to 15 5 -160

°

C . by a coil through which superheated steam undera pressure of 6-65 atmospheres is passed . Th e tar

i s screened,to free i t from solid fragments , and i s

then fed into th e top of the column ,whilst th e soft

pitch run s out at th e lower end into a montejus ap

paratus . Th e distil late escapes through an Opening



by producer gas or by means of an oi l burner , in orderto obtain a con stant temperature . The preheated tarflows through th is stil l at a temperature Of about300

°

C .,passing thence to a scrubber wh ich i s heated

to th e same temperature and in to which superheatedsteam is blown in order to extract th e volat ile constitu ents from th e tar . The residue collecting inth e bottom of the scrubber con si sts entire ly of pitch .

The d istillate i s then fractionated by cooling it instages

,and the various fraction s ar e col lected separ

ately .

The on ly other systems which need be ment ionedhere ar e : th e Wernecke process (Ger . Pat .

in which the tar i s allowed to flow over a

number of annular troughs,arranged in steps in a

hopper-shaped vesse l,in order to Obtain more com

plete utilisation of th e heat and th e Bocke lmann and

Sachse vacuum proces s (Ger . Pat .

CHAPTER V

TH E GAS LI QUOR .

THE gas liquor consist s of the con stituen ts whichcollect in the form of an aqueous liquid

,together

with th e tar , in the hydraulic main and condensers,

and as th e tar - free dr ainings from th e ammoma

washer . Th e liquor Obtained by condensation,as

mentioned in the preceding chapter,i s separated from

th e tar in the tar pit , and i s r un into a collecting

pit with th e washing wa ter .

Gas liquor i s ye llowish to deep orange in colour .

I n addition to ammonia , i t smel l s of sulphurettedhydrogen and tar . Chemical ly speaking

, gas liquorconsists of ammon ia ,

ammonium salts and volatileconstituents of tar , especial ly pyridin and phenol s .The ammon ium sal ts may be divided into twogroups according to th e re lat ive difficulty ex

per ienced in decomposing them . To the readilydecomposable salts belong ; ammon ium sulphide

,

ammonium cyan ide ,ammon ium sulphydrate and th e

three forms of ammon ium carbonate . The morestable salts a r e : ammon ium chloride

,sulphate

,sul

phite ,thiosulphate

,thiocarbonate and ferrocyan ide .

(53)

5 4 COAL GAS BY-PRODUCTS

I t is not advisable to store gas l iquor very long ,because , as L indner has shown

,in these circum

stances the proportion Of th e more stable sal tsincreases . I n such case -the consum ption of lime

al so increases,thus adding to th e cost of pro

duction .

TE STING GAS L IQUOR .

Th e most valuable constituent of gas liquor I S

th e ammon ia . Attempts to recover th e cyanogencompounds have not proved successful in practice

,

owing to th e smal l proportion present,

e spec ial lywhen the cyanogen washing process has been carriedout beforehand . Before proceeding to recover th eammonia it i s necessary to know both how much i spresent in th e free state and how much is combined as stable salts ; and it is to ascertain thesedata that the examination of the liquor is chieflydirected . The amount of the stable salt-s indicatesthe quan tity of l ime that must be added for theirdecomposition . There i s no need to go in to theexamination for the acids with which th e ammon iai s combined

,these being unimportant and non

essential .The total ammon ia 1s determined by disti l lation

in presence of l ime . Caustic soda should not be

used for this purpose,because th is reagen t also

liberate s as ammonia the nitrogen of the cyan idesand thiocyanates presen t

,and thus gives results in

exce ss of the truth .

TH E GAS L I QUOR 55

The distillate i s cooled , and then col lected in acidof known strength , th e exces s of acid being afterwards t itrated with equal ly strong caustic soda .

Th e percentage of ammonia i s obtained from th e

di°

er en ce between the original volume of the acidand the excess as found by the t itration

,1 c .c . of

normal acid corresponding to grm . ofammon ia .

To determine th e ammonia i n combinat ion as

unstable salts , that i s to say salts which split up at

100°

C . into ammonia and free acid, th e same

apparatus is used as in th e total ammonia determinat ion ; but a correspondingly larger vo lume oftest liquor i s taken and no milk of lime is added .

To determine the fixed ammonia,th e residue

from this last di st il lation may be diluted with waterand redistilled after adding milk of lime ; but inmany cases i t i s su

”'

icient to cal culate the fixedammonia from th e difference between th e total andthat in unstable combination .

Th e amount of active substance (CaO ) in the

lime i s ascertained by rubbing down an averagesample , and placing a we ighed quan tity ( 70 grms . )in boi ling distilled water . After st irring th e mixture thoroughly and al lowing th e l iquid to cool

,th e

volume is made up to 1000 c .c . ,and an aliquot part

(20 c .c . ) of th e wel l- shaken liquid is treated wi thtwo to th ree drops of ph enolph thale in and titratedwith normal sulphuric acid unti l th e r ed colorationdisappears . For the proportions given above ,

1 c . c .

of normal ac id corresponds to 2 per cent of active l ime .


TREATING TH E GAS L IQUOR .

Th e gas l iquor from the pit or tank contain s1 -3 per cen t Of ammonia . As this quantity is toosmal l to make the carriage of th e crude l iquor to adistance profitable ,

th e l iquor must be concentrated,

no mat ter for what purpose it i s intended . I t isth erefore customary in gasworks to concen trate thel iquor to a strength of 10 per cent or 25 per cent ofammonia

,or e l se to convert the whole of th e

ammonia into sulphate ; I n some large works,

strong ammon ia is produced , but in'

the maj or I ty ofcases the concentrated liquor is sold to firms whomake a special feature of treating this material .The s implest way to concen trate the ammonia

,

and one which dispen ses with d istil lation,is to

convert it into sulphate of ammon I a ; but thisprocess is mostly confined to small works

,where the

quantity of gas-liquor to be dealt with is not large .

Commerc ial sulphuric acid (66°

B é. strength ) orwaste acid is diluted by runn ing it through a siphon

,

as a thin stream in to gas liquor in a wooden vat .

This d ilute ac1d is then added to th e gas liquor inthe pit until th e mixture just turn s blue l itmuspaper r ed . Since sulphuretted hydrogen i s liberatedin this operation

,the work should be carried on

out of doors,a cowl be ing placed over th e pit, to

carry off th e poisonous fumes . Th e sulphate ofammonia l iquor thus Obtained is concentrated bymean s of the heat of th e flue gases from the retortfires

,a number of long iron pans

,l ined with lead ,

THE GAS LI Q UOR 57

being placed in theflue and charged with th e liquor,

which evaporate s until th e salt crystal lize s out .The sulphate crystal s ar e separated from the

mother liquor by mean s of a centrifugal separatorThe product i s an in ferior grade of

sulphate of ammon ia,though con tain ing about

20 per cen t of ammon ia,the colour being a dirty

dark grey from th e presence of tarry matters derivedfrom the gas l iquor .

THE D I ST ILLATION OF GAs L IQUOR .

Th e process almost exclusive ly u sed for concentr ating gas liquor is one of distil lation . As alreadymentioned th e l iquor contain s stable ammoniumsalts in add ition to free ammon ia and easily decomposable salts . The principle of the treatmen t i s todistil the ammonia and un stable sal t s o first

,by

warming the l iquor to th e boiling point of water .When this h as been done

,the stable salts ar e

decomposed with lime,and th e ammon ia set free is

recovered by dist illation . The reason for not adding the lime until th is second stage i s because ,

inthis way ,

the l ime is ut il ized to th e best advantagefor liberating ammonia from th e more stable sal ts ;whereas i f it were added before the first distil lationa large proportion would be consumed in combiningwith the carbon dioxide—a considerable quan ti ty ofwhich i s con tained in the gas l iquor and is expe l ledat th e same time as the free ammon ia—withoutproducing any corresponding yield of ammonia .


At one time any Old boiler was con sidered goodenough for th e first d istillation of gas l iquor . The

boiler was charged'

with l iquor and fired until al l

the volatile ammon ia had been driven off, afterwhich it was fi l led up again and the operationrepeated

,un til the remain ing l iquor had become

sufficien tly concen trated in fixed salts . On th isstage being reached

, the l ime was added,and th e

fixed ammonia d ist il led off.

This method was improved by arranging a

number of boilers s ide by side,and utilizing the

flue gases ‘

fr om the first one to heat the others .Th e disti lled vapours passed through the wholeseries of boilers in succession and thus becameenrich ed with ammonia . When al l th e read ilydecomposable ammon ia had been expel led in thisway ,

the.whole of the residual l iquor was pumped

into the first boiler of th e series , and there freedfrom th e ammon I a in th e stable salts after additionof th e calculated amount of lime needed for theirdecomposition .

This in termittent method is now practical ly discontinued in favour of continuous disti llation . The

apparatus constructed by Franke (Bremen ) for thispurpose con si sts of a still , divided into two compartments (approximate ratio 3 2 ) by a horizontal part ition . From the lower compartment a pipe forcarrying O th e ammonia vapours ascends th roughth e upper compartment

,and leads thence to th e

condenser and concentrated liquor tank . Both com

par tments of th e stil l ar e fitted with pressure gauges ,



Th e plant i s arranged in such a way that the l imeis not added un til al l the volat ile ammonia has beendriven o

”

. The steam used for heating th e apparatus is derived e ither from th e gas l iquor itself ore lse from a steam boiler . I t is employed

,in the

first place,for expe lling th e ammon ia liberated by

th e lime treatment ; then for mixing th e l ime chargewith water ; and final ly for driving 0 the freeammonia in th e gas l iquor , after which , laden withthe whole of th e ammonia from the gas li quor , itpasses to th e condenser .

‘

Th e heat l iberated duringcondensation serve s for preheating fresh quantities of

gas l iquor , for wh ich purpose the heat of th e spent

gas liquor —efflu ent—can also be utilized .

Th e continuous dist il lation of th e ammonia l iquoris based on the same principle which led Sava lle todevise th e column stil l for rectifying a lcohol . Th e

whole sys tem of the d istillation of gas liquor i s basedon three phases : expuls ion of the volatile ammon iaaddition of lime ; expulsion of th e ammonia combined as stable salts .This subdivision of the working process necessarily

implies a corresponding subdivision in the arrangement of th e column still . Th e three parts of th eapparatus ar e d isposed in such a manner that the

gas l iquor from a high-leve l tank traverses them in

succession . Both the upper and lower parts of thecolumn ar e divided into a number of superimposedcel l s

,whilst the middle portion is occupied by the

l ime mixer,which in the newest pattern s consists

of on ly a single ce ll . Th e gas liquor is led away

THE GAS LI QUOR 61

through tubular connections wh ich project a shortdistance above the floor of each cel l , so that a cer taindepth of the l iquor remains in each

,wh ilst th e sur

plus overflows into th e cel l next below . Each t ubei s long enough to dip below th e level of th e liquor ineach case ; and the tubes ar e arranged so that th el iquor traverses the cel ls in a z ig - zag course . Th e

steam which carries 0 th e ammon ia vapour passesupward from one cel l to another through perforationsarranged in the cel l bottoms and extending upwardthrough same in the form of short trunco- con ica ltubes which ar e long enough to project above th e

leve l of th e gas liquor and ar e surmounted by loosecaps supported by tripods resting on the ce l l floor .These caps dip be low the level of the gas liquor and

ar e provided with notches . I n passing from one

ce l l to another th e steam is compelled to make itsway through the l iquor in the upper ce l l , and as itdoes this by bubbling through each of th e notchesprovided in the caps , i t comes into intimate contactwith th e l iquor and become s enriched with ammonia .

Th e steam enters the ap paratus by the bottom cel land leaves it at the top one

,whilst th e warmed gas

l iquor travels in the Opposite direction,and parts with

th e whole of its ammon ia before issuing from the

bottom cell . The coun terflo’

w principle i s thus amply made use of in thi s arrangement

,th e hot fresh

steam coming into con tact with th e warm liquorwhich is poor in ammonia

,and taking up from th e

latter mere ly the fixed ammon ia which has just beenl iberated by th e l ime

,whilst th e steam that is fully


laden with ammon ia comes in contact with the fresh

gas liquor .

A few types of this kind of apparatus will now bedescribed .

, Fig. 2 represen ts a column stil l made by th e

Berlin-Anhal t Maschinenbau Aktiengese l lschaft . I t

i s built up of a number of flanged cast-iron rings,

superimposed on a pan which is provided with a

mping bottom ,th e whole be ing surmounted by a

cover . Th e steam and ammonia escape through A.

The ce l l bottoms already men t ioned ar e mountedon the internal flanges of the rings . Th e ce l l s ar e

provided with Openings,for cleaning purposes

,and

the whole interior is accessible,so that th e whole stil l

can be cleaned out without having to be taken apart .Th e preheated gas l iquor enters the top cell througha lateral feed pipe , B ,

and flows downwards from ce l lto ce l l

,meeting a current of steam on its way . The

course taken by the steam is indicated by the l ightcoloured arrows

,and that of the gas liquor by the

black ones . As the steam flows through th e crudel iquor at the loose caps it gradual ly rai ses th e sameto boiling

,so that , in th e . upper part of the apparatus

,

the volat ile ammon ia and the other gases pass intothe steam . The l ime i s added in the third ce l l frombottom

,in wh ich section th e tubes and caps ar e

made higher,so as to provide fer th e increased

volume of l iquor due to the addition of the milk of

l ime . Th e deeper immersion of the caps causes thel iquor to be kept in active movemen t by the steam .

The milk of lime,in slight excess , i s in troduced

THE GAS L I QUOR 63

through a lateral pipe C ,and mixed with the water .

I n th e two bottom ce l l s th e fixed ammon ia i s ex

F I G . 2 .—Co lumn st i l l . A—A : steam and ammon ia gas ; B

ammon iacal l iquor ; C mi lk of l ime ; D steam ; E to

spent l ime pit .

tracted from the gas liquor . The effluent, whichshould con tain on ly about per cen t of ammonia ,


i ssues from the apparatus through a se lfladjustingdraw-Off valve , g, which consists of a movable floatmade of sheet-iron , faced with lead , and carries the

cone valve on an iron rod . Th e float i s housed in a

cast- iron casing and i s subjected to the same steampressure as the rest of th e lower portion of the stillso that the water leve l at which th e valve Open sremains constant . The steam admiss ion pipe D isprovided with a pressure gauge

,a throttle valve and

a safety valve . Th e working steam pressure of the

apparatus is on ly1 1 4- 1 lb . ,

and th e safe ty valve i sset to blow 0 should that pr essu1 e be exceeded .

Th e effluent gas l iquor has a temperature of 212 °

F . ,

and 1s used for preheating the fresh l iquor in an

apparatus of the kind shown in Fig. 3,which i s

made by the same firm as the st il l . This i s of thetubular pattern ,

and the tube s ar e traversed fromabove downwards

,by th e hot e ffluent l iquor from

the sti ll , whilst th e fresh gas l iquor flows upwardthrough the cylinder

,and is thereby warmed to about

60 70°

C . ( 140 1 5 8°

F . ) before en tering th e columnstill . The admission of th e gas liquor is adjustedby a feed regu lator whilst th e supply of lime to th es till is controlled by a hand -pump or an automaticsteam pump .

Th e °Koppers s ti ll differs from th e one justdescribed

,both external ly and in ternal ly . I t con

si sts Of two portion s and only the volatile ammon iai s expel led , and th e mixing of th e l ime and gas

l iquor eM

ected ,in th e main column . Th e vessel

for mixing the milk of lime con sists of a single,

THE GAS LI QUOR 65

funnel- shaped chamber . The gas l iquor , deprived ofits volatile ammon ia,

en ters the mixing vesse l , alongwith th e milk of lime

,at the lowest poin t and at

F I G . 3 .-Tubu lar pr eh eater .

a point about hal f -way up the side of th e vesse lth e mixture run s off through a pipe in to an inde

pendent auxiliary column ,in which th e fixed

ammon ia is expel led . The escaping gases pass underneath the lowermost ce ll into th e mixing vessel . Th e

5


Openings in th e ce l ls , for th e passage of th e mixedsteam and gases , con sist of two long , narrow slits ,with loose caps of corresponding shape ; and thosein th e various cell s ar e arranged crosswise withrelation to those above and below . Di stil lationproceeds in th e mann er already described . Th e

separation of th e two stages of th e process has th eadvantage that th e auxiliary column can be cleanedwithout taking apart the whole of th e apparatus .The gaseous mixture issuing from th e column

contains a large proportion of steam ,toge ther with

ammonia ,sulphuretted hydrogen and carbon dioxide .

A wate r -cooled condenser , for concen trating th e

ammon ia ,i s mounted over th e column . The gas

liquor may al so be utilized for condensing . Th e

conden sed steam run s back into th e top ce l l of thesti ll . A reflux condenser of this kind is illustratedin Fig. 4 ,

in which the pipe A i s shown at rightangles to it s r eal

‘

position .

Th e gas is suing from the sti ll is mostly con

taminated with carbon dioxide and sulphuretted hydrogen . I f strong ammonia liquor were produced

,

th e carbonates would be liable to deposit in the

condenser and choke it , so that continuous workingcould only be obtained at the cost of very carefulsupervision . On leaving th e apparatus , the gasesar e pumped to their further destination . Any ob

struction in th e conden ser would set up increasedpressure in the still

,on th e one hand , and on th e

other a vacuum would be produced between thereand the pump . I t follows therefore that any such



deposition of salts would upset the whole seriesOf operations . Consequently , the concentrated gasl iquor must be freed from carbon dioxide beforeentering th e conden ser .Two principal methods have been proposed for

el iminating th e carbon dioxide from th e st ill gases .E ither th e carbon dioxide is absorbed by passingth e e nent gases from th e stil l through milk oflime

,or else u se is made of th e fact—wh ich will be

more fully explained later on—that th e gas liquorgives 0

"

carbon dioxide and su lphuretted hydrogenwh en warmed , whereas th e ammonia is retained .

Th e fi r st named prin ciple i s embodied In a carbondioxide separator , manufactured by the BerlinAnhal tischer Maschinenbau A. G . and il lustrated inFig. 5 .

This separator con sists of a cylindrical cast-ironvesse l , provided" with a conical bottom . Th e coveris provided with two open ings , of which the one inth e centre i s traversed by a pipe (T) which extendsnearly to th e bottom of th e vesse l

,where it i s

flared and notched . Through this pipe,at B

,th e e u

ent gases from th e column stil l en ter th e separator .The pipe i tself 1s surrounded by a number of platesmping at an angle to the horizon tal . Th e milk oflime 1s introduced from th e bottom (D) and flows awaythrough a lateral pipe (C ) hal f-way up th e vesse l . The

gas , freed from carbon dioxide , i ssues from th e

purifier through th e second pipe (A) in the cover . Th e

plates ar e arranged in such a way that the gas i scompe lled to describe a zig-zag course through the

TH E GAS LI QUOR 69

liquid. The milk of lime run s in to th e lime vesse l

of the column still , and i s there freed from th e

FI G . 5 .-Carbon -dioxide separ ator . A pur ified ammon ia gas

B ammon ia gas and CO C to sti l l D m i lk of l ime .

ammon ia i t has absorbed , thereafter serving toliberate the fixed ammon ia . The purified gas i sthen forwarded to th e conden ser .Th e separation of th e carbon dioxide by warming


th e gas liquor is based on th e following con sideration s Ammon ium sulphide and ammon ium carbonatebelong to th e most readily decomposable class ofsalt s , that i s to say they ar e decomposed by heatinto ammon ia and carbon dioxide

,or sulphuretted

hydrogen , respective ly . Now ,warm water has a

greater capaci ty for absorbing ammonia than i t hasfor carbon dioxide and sulphuretted hydrogen

,so

that if a solution of ammon ium sulphide or am

monium carbonate be warmed,i t becomes enriched

in ammon ia at th e expense of the sulphurettedhydrogen and carbon dioxide . E xperimen ts performed by Berte lsmann with gas liquor in a Feldmann column still showed that gas l iquor ceasesto absorb carbon dioxide when th e temperaturereaches 96

°

C . (205° F . )—see th e subjoined Table ,

in which the conten t of ammon ia,carbon dioxide

and sulphure tted hydrogen i s set down as 100. The

column stil l was composed of eleven cel ls ; and duringth e experimen t

,determinat ions were made of the

temperature in each cell,and al so of th e amoun ts of

ammon ia ,carbon d ioxide and sulphuretted hydrogen

in th e l iquid .

I n th e first five cel ls , in which th e temperaturerose to 93 °

C . , th e gas con ten t in th e water increasescon tinual ly

,th e ascending vapour giving up a

portion of the gases to the water again . I n th e

sixth cell,in which th e temperature attain s 96

°

C . ,

th e percen tage of carbon dioxide dimin i shes by one

half, and that of the sulphure tted fal ls by more than5 0 per cen t , whereas th e water stil l con tain s 1 70

THE GAS LI QUOR 71

per cen t of ammonia . Up to th e n inth cel l th etemperature rises to 9 7

°

C .,and whilst practically

th e whole of th e carbon dioxide has been expel led,

the ammon ia con ten t still amoun ts to 26 per cent .

Gas Content of the Water in Percentages ofO r igina l Amount .

Water Sample Temperatur efrom I ntake of OC .

Su lphur ette dAmmon ia. Car bon Dioxide .

H ydr ogen.

Hence,i f th e crude gas liquor be kept at thi s

temperature before i t i s admitted to th e columnstill

,a l iquor very low in carbon dioxide will be

Obtained . Th e Fe ldmann -Pin tsch separator i s basedon th is principle

,and con sists of a cast—iron cylinder

divided in to two parts . Th e gas l iquor , preheatedby th e e uent from th e column still

,i s in troduced

in to the lower part of th e apparatus and i s heatedby a steam coil to 88 9 5 °

C . ,which causes i t to

give 0M

carbon diox1de , sul phu r etted hydrogen and

al so ammon ia . Th e liberated gases pass in to th eupper part of th e separator , where they come incon tact wi th a cur rent of cold gas liquor , whichabsorbs th e ammonia complete ly , leaving th e carbon


dioxide and sulphuretted hydrogen to escape in toth e open air .

WORK ING THE STILL .

Starting th e apparatus for the continuous distil lation of th e gas liquor is a very simp le operation ,

all that is necessary beforehand be ing to employ theusual precautions to see that none of the apparatusis leaky . Heating up should be effected slowly

,and

it is not unti l the entire con ten t s of th e still ar eproperly warmed through that the fir e should be

quickened,to rai se th e l iquid to boiling . When th e

con tents ar e drawn off,the fir e should be ex

tinguished .

I f milk of lime be used from th e start,the liquid

should be stirred up from time to time,to prevent

th e l ime burning on to the metal,s ince

,in addition

to th e loss of heat , th i s would give rise to th e usualdangers of boiler Incrustat ion .

Th e con tinuous column still s ar e heated by directsteam . Before starting

,th e still shou ld be warmed

up in the dry state,the water of condensation from

the heating steam collecting in th e bottom of thecel ls . The admission of steam is gradually in

creased , and at the end of about two hours , thepressure should attain 1 7

12-3 lb . per square inch . The

gas l iquor is then admitted , and the pressure is

main tained by con trolling th e supply of steam . As

soon as th e er'

uent water begin s to drain Off,th e

milk of lime i s added ; and the temperature i s

TH E GAS LI QUOR 73

raised,by admitting more steam , un ti l no more

volatile ammonia can be detected in the ce ll abovethe lime mixing vesse l . Th e inflow of milk of limei s then regulated in such a manner that th e e

M

uen twater i s free from combined ammonia as we l l .Th i s cond ition can be ascertained by testing a

sample of the effluent with a l i ttle fresh lime,under

which conditions no smel l of ammon ia should benoticeable . After the admission of the steam , gas

l iquor and milk of lime has been properly adjusted,

care must be taken to see that the supply of eachremains constant throughout th e whole of the

distillat ion process , th e effluen t liquor being testedfrom time to t ime to make sure that everything isin order . I f the steam pressure be too high ,

the

gas liquor i s l iable to be forced into the gas dehverypipe . To test whether this i s th e case , a hole . i sbored in th e ammon ia pipe

,and . if th e steam which

then e scapes con tains mo1stur e—wh ich may be

ascertained by holding the hand in th e e scapingcurren t , whereupon any moisture presen t will makethe hand wet—th e supply of steam must be r e

duced .

I n the course of distillation the temperature willfal l un less th e supply of steam be increased

,owing

to the wal ls and bottom of the cel ls becomingincrusted with lime . For thi s reason th e columnshould be cleaned out

,by means of th e manholes ,

at th e end of every month or two .

One of th e most troublesome obstructions to theWorking of the still i s caused by tar passing into


the column ; but this drawback can be prevented bycareful supervision of th e pumps and the ammonialiquor pits . I f

,notwithstanding

,any considerable

quan tity of tar finds its way in ,about th e on ly

thing that can be done i s to dismoun t the apparatusen tirely and clean i t out .Th e con sumption of fuel depends on th e nature of

the fue l and th e con struction of the still . Withth e Feldmann-Pintsch apparatus , 4 cwt . of steamwill be required

'

for th e disti llation of 220 gals . of

gas l iquor , so that , given an evaporative power of43 ton s of coal wil l be needed in treatinggal s . of gas l iquor .

PREPARATION OF CONCENTRATED GAs L IQUOR .

Although a method of Obtaining 10 per cen t gasl iquor has long been known , a higher concen trationi s generally desired , and for this purpose a con

tinuou s process is exclusive ly employed .

As a rule,two grades of concentrated liquor ar e

produced : a weak l iquor containing 16-20 per cen tof ammonia

,and a stronger l iquor with 18 -25 per cent .

The weaker liquor has a den sity of 15 -18°

Bé. ,

and con tains a large proportion of ammon ia in

combination,chiefly as carbonate . I t i s prepared

without th e employment Of'

a carbon -dioxide separator . Th e manufacturing process may be i llustratedby reference to th e plan t made for this purposeby th e Julius P intsch A. G . (Ger . Pat . and

illustrated in Fig. 6 .

Th e crude l iquor runs from a high - leve l tank to



THE GAS LI QUOR 77

Th e steam enters th e lower chamber , 6, flowsthrough th e cap

-covered Open ings in th e bottom ofthe several ce lls

, and becomes saturated with am

mon ia, ammonium carbonate and smal l quantities

of ammonium sulphide . Th e ammoniacal vapoursar e conden sed in a conden ser , m,

and ar e deliveredto the storage vesse l , p . This vessel i s emptied bycompressed air , furn i shed by th e compressor , g.

This plant will produce a l iquor containing up to18 per cen t of ammonia,

assuming th e crude l iquorto have an average content of 20 per cent of combined ammonia .

I n order to obtain the stronger grade of ammoniacal l iquor (up to 6

°

Bé. strength) , it i s necessary tofree the gas liquor from carbon dioxide . As has

already been seen , this el imination of carbon d ioxidecan be effected in two principal ways . One of these—th e warming of the gas liquor—forms th e basis ofthe apparatus illustrated in Fig. 7 and embodyingth e Fe ldmann-Pin tsch system . I t d iffers from the

apparatus just described , for th e production of weakammonia l iquor , by contain ing a carbon-dioxideseparator , t, and a reflux conden ser

,33, mounted on

the column still . Clarified water alone i s used forcondensing the waste bases in s .

The crude l iquor flows from th e bac ock tankinto th e ammonia absorber

,r,of th e carbon dioxide

separator , t, whence it i s passed through th e pr e

heater , to be warmed by th e eM

uent water fromth e column still . Th e preheated liquor is nextheated to 88 -9 5

°

C . in the heating chamber , 8 , of th e


THE GAs LI QUOR 79

separator , t,by a steam coil , and parts with its

carbon dioxide . Any ammonia carried off at th e

same time is reabsorbed by the crude l iquor in r .

The liquor freed from carbon dioxide i s disti lled in

the column still , OZ. I n order to concentrate the

ammon iacal vapours , a portion of the steam is condensed in th e reflux conden ser , on, mounted on the

stil l . The further course of the process is identicalwith that given in connection with the preparation ofthe weaker grade of liquor .To prepare concentrated ammonia l iquor by r e

moving the carbon dioxide with l ime,the separator

i llustrated in Fig. 5 is employed . Th e gas liquorflows from th e high- leve l tank through a cel lularcondenser of the kind shown in Fig. 8

,where it is

preheated,and at the same time the sti ll gases ar e

condensed . The preheated liquor is distil led in the

column still, and th e gases from the latter ar e freed

from steam by th e reflux condenser,from which they

pass into th e carbon dioxide separator,in which

both the carbon-dioxide and th e sulphuretted hydro

gen ar e absorbed . The outflowing gase s ar e

condensed in the cellular conden ser and conveyed tothe storage vessel . The milk of lime used forpur ifying th e gases is r un into the l ime mixer of th estil l

, and there serves to expel the combined am

monia .

The concentrated ammon ia l iquor resemb les thecrude gas l iquor in appearance

,and

,l ike the latter

,

darkens in colour on standing . I ts value i s asoertained by a simple titrat ion ,

10 c .c . be ing diluted to


FI G . 8 .—Cel lu lar condenser . A cr ude l iquor to st i l l ; B

cr ude l i quor fr om tan k .

TH E GAS L IQUOR 81

1000 c .c . and an al iquot part be ing treated with an

excess of normal sulphuric acid . After boiling for a

short time the excess of sulphuric acid is titratedback with normal caust ic soda

,methyl orange being

used as indicator .

Th e concentrated l iquor is not,in itsel f

,a com

mer cial article,but forms th e raw material for the

manufacture of ammon ia preparations , and i s therefore a semi -manufactured product .

PREPARATION OF AMMON IA .

Th e most valuable products recoverable from gas

l iquor ar e aqueous ammonia and l iquefied ammon ia ,the

former being a chemically pure product obtained byabsorbing ammon ia in distil led water . I t i s r e

covered direct from the gas l iquor , without th e assistance of any other chemical agents , such as acids orsalts

,and differs from the crude gas liquor in bein g

free from any contamination with carbon dioxide ,

sulphuret ted hydrogen or organic (empyreumatic )substances . I n conn ection with the preparation of

aqueous ammonia,Pfe iffer ofMagdeburg has rendered

valuable service . I t i s prepared , e ith er by the intermittent process in boil ing pan s

,or by th e con tinu

ous process in column stills . The gases from th e

pans or still s ar e freed from con tained acids by milkof lime and ar e then dried , the dried gases beingfi ltered through wood charcoal (and also throughvase line oil i f necessary ) to e liminate organic substances

,chemical ly pure gaseous ammon ia being


finally left . The furth er treatment of this gas can

be carried out in two ways . For th e production ofaqueous ammon ia it is passed in to distilled water ,whilst for making liquefied ammon ia it is put througha compressor .The intermittent process of preparing aqueous

ammonia i s carried on in the following manner :The still is charged half full with the crude liquor

and s lowly heated,the gases l iberated during this

stage be ing returned to the crude liquor tank . Whenthe liquor has reached distillation temperature (100

°

a calculated quantity of milk of l ime i s added at

once . The gases disengaged ar e passed into a highreflux condenser

,two ce l ls

,provided with loose caps ,

be ing interpo sed between the st il l and conden ser , inorder to prevent any l ime from be ing carried O

M

withthe gases . Th e addition of th e milk of lime beforedistillation causes practical ly th e whole of th e car

bon dioxide and sulphuretted hydrogen to be retainedin th e sti ll . The high reflux condenser condensesthe whole of th e steam

,which then flows back into

the still , carrying with it a por tion of th e ammoniaand th e final traces of carbon dioxide and sulphurettedhydrogen . The gas , dried in this way ,

is next passedthrough several cyl inders charged with wood charcoal , in which the empyreumatic substances ar e ab

sorbed . The final traces of carbon dioxide and

sulphuretted hydrogen ar e extracted with causticsoda, leaving the gaseous ammonia chemically pure .

To prepare aqueous ammonia,thi s gas i s introduced

into a cyl inder con taining dis til led water , the ab



requires to be carefully con tro lled,th e gases being

subjected to constant examination,for the presen ce

of sulphuretted hydrogen,after th e wash ing w i th

caustic soda .

I t i s on ly of late years that th e preparation ofaqueous ammon ia by th e continuous process hasbeen carried on with success . Th e Be r lin -Anhal tischeMasch inenbau A. G . , in collaboration with Grunebe rg , Tieftrunk and Buhe

, was th e first to d evise a

process of th i s kind on th e large scale, W I th which

it Was found practicable,in an Upper Si lesian works ,

to treat nearly 1800 gal l s . of gas l iquor in twentyfour hours .From that time onwards

,th e continuous process

has developed progressive ly . Th e plant now suppl iedby the above firm is based main ly on th e paten tedcarbon -dioxide separator and the grouping of th e

apparatus in such a way that , throughout the process ,th e milk of lime flows in th e opposit e direction tothat taken by the ammoniacal gases .

The working of th e process i s checked by test ingthe effluent ; and so long as th e latter con tain s an

excess of lime,it is evident that such exces s i s a l so

present through out th e process . Th e ammon iacalgases issuing from th e s ti ll ar e passed through a r e

flux condenser which e l iminates al l but a slight traceof steam from th e gas . Th e latter still containscarbon dioxide ,

sulphuret ted hydrogen and empyr eu

matic substances , the first two of wh ich ar e com

p letely removed by passing th e gas through a seriesof th ree milk-of- l ime vessel s (Fig. such as ar e

TH E GAs L I QUOR 85

used in concentrating th e crude gas l iquor , and in

which the milk of lime flows in the opposite direct ionto that of the gas and runs O

M

into th e stil l . Th e

gas passes through two condensers and a coke fi l ter,

F I G . 9 .—L ime wash er .

after which the bulk O f th e ch ief Organic impuritiesi s removed by an oil washer

,and th e remain ing im

puri ties Of al l kinds by charcoal fi l ters . Th e gas issuing from the last named is pure ammon ia

,and i s


passed into distil led water in a cooling apparatuswhich enables aqueous ammon ia of any desired con

cen tration to be obtained .

Th e carbon dioxide. and sulphuretted hydrogen can

also be e l iminated by th e application Of heat and a

Fe ldmann-Pintsch plant for this purpose i s il lustrated ,diagrammatical ly , in Fig. 10. The column sti lldifler s from that already described in that the milkOf- l ime mixer is abolished

,the l ime reagent be ing

applied prior to th e distillation process . Up to th estage Of i ssuing from the heating chamber of th ecarbon -dioxide separator , the course taken by thecrude liquor is exactly the same as in the preparationOf concen trated gas liquor ; and there i s also no need

,

in this case ,to warm th e gas liquor before i t en ters

the heating chamber . Th e liquor is passed alternately in to two mixing vesse ls , f ,

which ar e chargedwith the n ecessary amoun t Of milk of lime by mean sof a steam syphon ,

i t be ing th e intention that th el ime shall combin e with the acid s of both th e fixedand more volati le ammon ia sal ts , the latter of whichar e presen t in smal ler quan tity , and thus furn i shperfectly pure ammon ia gas . The arrangemen t ofthe plan t enables th e mixture of milk Of lime and

gas l iquor to be in troduced in to th e still whilst stil l hot .Th e pre liminary e l imination of th e carbon dioxideand sulphuretted hydrogen by heat enables up to 90

per c en t of the con sumption Of quicklime to besaved , if the operation s be accurate ly performed . Bymean s of the steam pump , 9 (shown in th e Figure as

situated between the two mixers , f ) , the power Of


which is al so utilized for stirring the contents ofthe mixers

,th e mixture is pumped in to the

column sti ll, d ,where the distillation i s carried on in

th e known manner . Th e reflux condenser , x ,retain s

n early the whole Of th e water vapour carried overwith th e gases . The dried gas passes through th e

safety device , It , in to the washer, i, which is chargedwith caustic -soda lye ,

which absorbs the residualtraces Of Carbon dioxide and sulphuretted hydrogenpresen t . I n th e gas i s cooled in order to removethe heat acquired in Wood charcoal or boneblack , in lumps about th e s ize Of peas

,i s employed

in two cylinders, O , for the purpose of absorbing th e

empyreumatic constituen ts . T h e purified gas i sabsorbed by distilled water in th e two absorptionves se ls

, p ,which can be connected up alternately

,

th e heat liberated by the absorption process beingremoved by mean s of a water coil .The requisite distilled water is recovered , in the

heating chamber 3,Of the carbon -dioxide separator t

,

th is water be ing distil led in q , freed from mechanicaladmixtures of iron by fi ltration through sand and

charcoal in y , and col lected in u . This apparatusenables techn ically pure aqueous ammon ia . that isto say , a water-white product free from chlorine , tobe Obtained . For preparing th e chemically purearticle

,the absorption vesse l s must be of earthenware

,

and the purifying agen ts must be renewed at morefrequen t interval s .

TH E GAS LI QUOR 89

L IQUEF IED AMMON IA .

Th e h ighe st -grade product obtainable from gas

l iquor is liquefied ammon ia . I t i s prepared in exactlyth e same way as ch emically pure aqueous ammon ia ,

up to th e absorption stage ,th i s latter Operation be

ing replaced by compressing th e gas in to the l iquidcondition

, after having passed it over quicklime inorder to make certain that th e gas i s perfectly dry .

For th e purpose of compen sating th e fluctuation s inpressure between the sti l l and the compressor , the

gas i s usually stored in a gasholder provided with an

oil seal . According to th e practice recen tly adoptedby the Pin tsch Company , th e gas i s conveyed directfrom the st ill to th e compressor , and any con siderablefluctuation s in the pressure ar e avoided by mean s ofseveral closed storage vessel s

,provided with suitable

pressure gauges .

The dried gas sti ll always con tains impurities , suchas pyridin

,methyl alcohol

,benzol and organ i c sub

stances . These ar e removed by repeated compression and r e -evaporation of th e ammon ia

,th e

impurities remain ing behind in th e liquid condition .

There i s nothing essen tial ly differen t between th e

manufacture Of l iquefied ammon ia and that of liquefiedgases ; and th erefore there i s no need to go in to detai l on th e subject . The liquefication i s entire ly on

a par with that of carbon dioxide and sulphur dioxide .

At 10°

C .,th e vapour ten sion of ammon ia i s about

6% atmospheres and any pressure exceeding this


value liquefies th e gas , at said temperature ,I n th e

compressor, th e thoroughly cooled gas i s subjected to

a pressure of 8 atmospheres . The nearly colourle s sl iquid is forced by the pressure in th e compressorthrough an Oil separator and a stee l cooling coi l , in tothe usual stee l flasks met with in commerce . I n

charging these flasks, an al lowance of about 5 8 cub .

in ches should be made for each 1 lb . Of ammon ia ,

under which condition s the fi lled flasks may be ex

posed to any temperature up to 65°

C . (149°

F . )without exceeding the pressure they have been testedto stand (14 20 lb . per sq . in ch ) .

Th e chief u se of liquefied ammon ia i s in refrigeratingmachines (L inde ice machines) . I n consequenceOf th e handy nature of th e stee l flasks , and the factthat th e ammonia is 99 -100 per cent pure ,

l iquefiedammon ia is now used in stead Of aqueous ammonia .

I t forms a water-white aqueous liquid,having a high

refractive index , and has th e sp . gr . 06 362 at zeroC . , the boil ing-poin t under normal pres sur e being

C .

SULPHATE OF AMMON IA .

Sulphate of ammonia is the product most usual lyObtained from gas l iquor , because , in con trast to concentrated gas liquor , i t is an article Of direct commer cial value , and i s also more conven ient to store .

I t i s prepared by passing the gases from th e columnsti ll in to dilute sulphuric acid , ammon ium bisulphate ,

which i s readily soluble in water,being formed



lead- lined separator , in wh ich paral lel surfaces ar e

arranged in such a manner as to compe l the gase s totraverse a zig-zag course . I f n ecessary

,th e effluen t

gases ar e r e-washed wi th sulphuric acid .

This type of plan t enables sulphate of ammoniato be produced by th e intermittent process

,at least

two absorption vats be ing provided , so that whenth e ch arge in one I s saturated , th e other can be

connected up,and vice versa

,without interrupting

th e distil lation of th e ammonia .

A Pintsch plan t for the in termittent productionof sulphate of ammon ia i s i llustrated in Fig. 11 .

The arrangemen t for d istill ing the gas l iquor issimilar to that used in making concentrated gasl iquor

, except that , whereas in that case th e crudeliquor is warmed up by th e gases escaping from th e

column still,the same e

”

ect is produced here byth e spent gases from the absorption vats ( saturators )

p ,in O . Th e gases from th e sti l l ar e admitted

,

under a l eaden bel l , in to the saturator . The smallamoun t Of ammon ia not taken up by th e sulphuricacid in th e saturators passes

, along with steam ,

carbon dioxide and sulphuretted hydrogen ,I n to th e

acid receiver , g,to re tain the ammonia ,

which comesover more particularly toward the end of th e saturation process in p . Th e acid receiver

, g (see Fig. 12)—Pin tsch ’

s Ger . Pat .—consists of . a closed

vessel , l Ined throughout with lead , and providedwith an in ternal vertical partition . The secondor discharge chamber con tain s a number of mpingbaffles , which prevent any of the sulphuric acid


from being carried away by the e'

nent gases . The

rece iver is fi lled,to about a quar ter of its height

,

with dilute sulphuric acid . The ammon iacal gasesfrom th e saturator ar e obliged to pass undern eathth e partition in order to reach the second chamber

FI G . 12 . Ac id r eceiver for sulphate of ammon ia p lant . Awaste gas con ta in ing ammon ia ; K waste gas fr ee from ammon ia ; U lye ; W su lphur ic acid .

and in this way th e whole of their ammonia i s combined by th e acid . Wh en th e charge in the one

saturator has been neutralized by th e ammon ia inthe gases , the latter coming from th e stil l ar e

diverted in to the second saturator . The sulphate of



escapes with the waste gases . On this accoun t,

therefore, Rosenkranz allows the exhaust gases to

e scape during the first stage,but when th e second

stage i s reached,diverts these gases into a fresh

saturator which is charged with fresh acid . As

soon as saturation in the first saturator is complete ,i t i s d isconnected and replaced by the second one .

F I G . 13 .—Z impe l doubl e be l l wash er .

The salt in th e first saturator is taken out, and the

apparatus is r echarged with fresh acid , to be readyfor the exhaust gases from th e other saturator to bepassed through it when the proper moment arrives .

The acid charge Of th e saturators should h ave a

density of about 4 2°

Bé. , under which conditions

THE GAS LI QUOR 97

the sulphate of ammonia i s deposited as largecrystals wh en th e saturation stage i s reached ; and

the resulting product is of a high degree of purity .

I t has mostly a greyish or ye llowish tinge , wh ich ,however , i s not objected to in commerce

,whereas

if th e sal t i s Of a blue shade ,i t must be sold at a

loss, although the blue colour—which is due to

Prussian blue from th e cyanogen impurities—i squite harmless when th e salt i s used as a fertil i zer .A blue tinge al so appears when local super saturation of the acid has occurred ; and for some unex

plained reason ,the salt Obtained from imperfectly

saturated liquor turn s blue in drain ing . Sulphateof ammon ia is sold on th e basi s of i ts ammon iacontent on ly

,this amoun ting as a rule to 24 -5 per

cent . Th e following Table give s th e solubili ty ofsulphate of ammon ia per 100 parts of water

, at

various temperatures

at 0°C . par ts at 60

°C. par ts

10°

70°

20° 80

°

30°

90°

40°

8160 100

50°

Th e manufacture of sulphate of ammon ia in

saturators , as described above,en tai ls stoppages for

the purpose of emptying th e apparatus and r e

charging it with fresh acid ; but th e process may be

carried on in a con tinuous manner by mean s Of th esame plant , by in troducing both th e mother l iquorand acid in the form Of con tinuous thin s treams .

Th e acid , however , must not be so s trong as in th e

in termitten t process , the stren gth employed being

7


32°

B é. The crystallized sal t is scraped out at interval s , or el se i s tran sported , by mechan ical mean s , alongwith th e mother liquor

,to a centri fugal machine ,

where the two ar e separated , the mother l iquor be ingr un back in to th e saturators .Latterly

,a number of gasworks have taken up

the manufacture Of by-products ; and

,so far as the

manufacture of sulphate of ammonia i s concerned ,the problem may be regarded as solved .

Th e two me thods Of B u r kheiser and Fe ld enablesulphate of ammon ia to be produced simultaneouslywith the purification of th e gas , thus rendering theOperation independen t Of the sulphuric acid manufacturer .The idea'

of combin ing th e sulphuretted hydrogenand ammon ia in such a manner as to form sul phateof ammon ia

,dates back as far as the fifties of the

last century,though no practical solution of the problem was effected . Th e attempts were al l wreckedin th e endeavour to convert th e sulphite in to sulphate ,and con sequen tly trials were made for util izing thesulphite as a ferti lizer . This step was rightly character ized by Fe ld as merely an emergency remedy .

The B u rkheiser process is described I n GermanPaten ts and

This inven tor oxidizes th e irori sulphide Of th e gas

purifying agent to sulphurous acid by a curren t ofair , and absorbs the product in a neutral solution ofammon ium sulphite

, ammon ium bisulphite be ingformed . The ammon ia of th e gas l iquor is distilledin a column sti ll

,and i s re turned , in a dried state , to

the crude coal gas before th e sulphuretted hydrogen



through scrubber I I , where i t encounters a flow

Pu

' r

m

of ammonium sulphite liquor,which absorbs the

dioxide and becomes bisulphite ,in which condition

i t i s r un through scrubber I and arrests th e

residual ammon ia in th e coal gas . The resultingsemi-neutral liquor passes to the saturators , where

the bulk of th e ammonia of the coal gas i s absorbed ,neutral sulphite Of ammon ia be ing formed . Thissalt , being very sparingly soluble ,

i s deposited for

the most part , and the residual n eutral motherliquor is used again for absorbing sulphur dioxide inscrubber I I . The deposi ted salt , about 60 per cen t Ofwh ich is already oxidized in to sulphate Of ammon ia ,

i s cen trifugalized,dried and completely oxidized in a

conveyor stove .

This stove con sists chiefly Of a horizon tal drum,

provided at one side with a charging hOpper for th eadm1ss10n of the mixture of sulph ite and sulphate

,

another open ing , for the discharge of the complete lyoxidized salt

,being provided at th e other side .

I nside the drum is a worm conveyor which tran sports the sal t from th e charging end to th e de livery end

,whilst a curren t of air traverses th e drum

in th e Opposite direction . For half i ts length ,

measured from the charging end,the drum is cooled

,

whilst the oth er half i s h eated . When th e mixedsal t enters the heated end of th e drum

,the sulphi te

Of ammon ia i s decomposed in to ammon ia and

sulphur dioxide,and is carried back by th e curren t

Of air—which partial ly oxidizes it at th e same time

in to th e cooled end of the drum,where it recon

den ses and i s moved onward again ,together with

the mixed salt,in to th e heated end of the drum ,

and

i

so on . Th e salt discharged from the drum isperfectly free from sulphite .

Of course , th e whole purifying plan t i s arranged insuch a way that the H 2

8 purifiers can be connectedand disconnected , according as they ar e regeneratedor exhausted . A smal l amount of sulphur trioxidei s formed along with the dioxide I n th e purifiersand comb ines with the ferric oxide to form sulphate .

As soon as any con siderable accumulation of this sulphate collects in th e purifying agent i t is extractedby lixiviation .

The oxidation in th e conveyor stove seems,how

ever,to be not quite complete

,or e l se a considerable

amoun t of sulphur dioxide i s carried away by th ecurren t of a ir and lost , for , according to a morerecen t process (Ger . Pat . B urkh eiser

does away with th e supplementary oxidation process ,and converts th e sulphur dioxide in to trioxidedirect

,by in terposing between th e purifier and

scrubber a contact mass of platinum or ferric oxide ,as in sulphuric acid making . I n other respects theprocedure i s the same

,except that sulphate l iquors

replace the sulphite liquors .

The B urkh eiser process h as emerged beyond theexperimen tal s tage and is already in use at the

Tege l gasworks , Berlin , and at several other gaswo rks and by

-product cokeries in Germany , e tc .

(Aachen , Hamburg and L iege) .

Whereas,in the B u rkh eiser process , th e trans

formation in to sulphate i s effected directly , by th e

aid Of atmospheric oxygen ,Feld employs poly



sulphate of ammon ia and sulphur being formed,

toge ther with some ammon ium th iosulphate . The

deposited sulphur is burned off as sulphur dioxide

and serves for regen erating th e absorbent liquidfrom th e thiosulphate (reaction

(5) 2NH3

°HzO (NHQ QSO,

(1111928 203 S .

(c) (N I—I4) 2S4O6 2+ 8H S 8H

2O + (NH )WS O 5 8 .

(d) (NH H) S Oi (NHH) S 2 (NH 4) 2S2O3 + S .

When the liquor i s su I ciently enriched withsulphate of ammon ia , a portion of it i s worked up

for - the recovery of sulphate ,by treating it with

sulphur dioxide and heat,thus converting the

polythionate in to sulphate , accompan ied with deposition Of granular sulphur

(NH4) 2S4O6 (hot) SO

228 .

The sulphur is separated from the l iquor , whichi s then concen trated to allow the sulphate of am

mon ia to crystallize out . The mother liquor , sulphurdioxide and sulphur ar e used over again in th e manufactur ing process .

Th e on ly direct oxidation occurring throughoutthe whole process i s th e combustion of the sulphurto sulphur dioxide

,th e further oxidation of the

thiosulphate to sulphate being based on a reactionof displacement between the thiosulphate and sulphurdioxide ,

accompan ied by th e deposit ion of sulphur .Th e Feld process has enabled a wet purification

for washing out the sulphuretted hydrogen to be

introduced in addition to purifying the coal gas and

producing sulphate of ammon ia .

CHAPTER VI .

THE TREATMENT OF TH E GAS -PURI FYI NG AGENTS .

THE spent purifying agen t s contain ,as valuable

con stituen ts : ammon ia ,cyanogen

,sulphur

,sul

phur ic acid and thiocyanogen,th e cyanogen be ing

perhaps the most valuable at al l . This substance i spresent in the spen t mass in the form Of compoundsOf still unknown composition . Th e percentage Of

cyanogen varies con siderably according to the originof the mass

, and i t i s therefore importan t , in connection with th e sale of spent gas purifying agents

,

to have a good method for th e determination of thecyanogen . Con sequen tly

,the divergen t character

and chemical composition of the purifying agen tshave l ed to the e laboration of a whole serie s ofmethods of determination

,th e most customary Of

which wil l now be briefly described . I n valuing thearticle it is importan t that both buyer and

'

sel ler

should agree on th e method of determination to beemployed , since otherwise it will be di

M

icu lt forconcordant results to be Obtained .

On e Of the O ldest methods for th e determinationOf ferrocyanogen i s that introduced by Z u lkowskyin 18 83 (D ingler , NO . 24 9

,p . I t was origin

(105 )


al ly intended for application to ferrocyanide melts,

but was afterwards used also for determin ingcyanogen in gas—purifying agen ts .

Th e mass i s extracted with caustic potash, th e

fi ltrate being then acidified with sulphuric acid,and

the cyanogen determined by titration with zincsulphate solution of known strength . Th e end

point of th e t itration i s ascertained with ferricchloride solution -as indicator .L eybold and Moldenhauer ( “ Journal fur Gas

beleuchtung ,”1899 , p . 15 5 ) ascertain the percentage

of ferrocyanogen by , determin ing the combined ironvolumetrically . The mass i s treated with causticpotash in th e warm ,

and is then made up to a

definite volume . An aliquot part Of th e fi l trate i sconcentrated , and i s evaporated with sulphuric acidand calcined

,to e liminate th e cyanogen . Th e

residue i s taken up with a little sulphuric acid inwater

,and the iron is determined in th e solution

,

with potassium permanganate ,in known manner ,

after reduction with zinc .

De Koningh Z eitsch r ift fur angewandte Chemie,

189 8,p . 463 ) evaporates the alkaline extract to

dryness and e liminates the cyanogen by fusion withsodium carbonate and saltp etre

,th e iron being

de termined , gravimetrical ly,

I n the melt . Th e

determination of the cyanogen in gas-purifying

agents by est imating the iron in the alkaline ex

tract has also been proposed by others ; but sincethis extrac t con tains other iron in addition to thatin combination with cyanogen , the ferrocyanogen



also be effected in a porcelain mortar , the l iquidbeing stirred

,at th e prescribed times

,with th e

pestle . At th e end Of th e sixteen hours,the thorough

ly triturated mixture i s rin sed in to a 25 0- c .c . flask ,

which is then fil led up with distilled water,to 5 c . c .

above the mark (to allow for the space occupied byth e solids) . The flask is then shaken up wel l . andth e con ten ts passed through a dry fi lter . Owingto the presence of impurities

,main ly Of an organ ic

character,the potassium ferrocyanide cannot be

determined direct by titrating th e fi ltrate,but th e

extrac t must first be r e -

pur ified by precipitating th ecyanogen as Prussian blue . Th e ferric chloridesolution used for thi s precipitation con tains 60 grms .

Of FezCl

6 per litre

, along with 200 c . c . Of cen centrated hydrochloric acid . One hundred c .c . of th ealkal ine extract ar e r un (with stirring) in to 25 c .c .

Of the ferric solution,which has been warmed to

80°

C . Th e ferrocyan ide i s thrown down as Prussian blue

,which is fi ltered through a folded fil ter in

a hot-water funn e l , this latter being kept coveredup and the solution warmed before each portioni s poured in . Th e precipi tate i s washed two orthree times with hot water

,and i s then stirred

up well,in a glass beaker

,along with 20 c .c . of

10 per cent caustic potash , in order to decom

pose al l th e Prussian blue,this process being assisted

by a careful,gen tle warming . When al l the blue i s

decomposed,th e con ten ts of the beaker ar e rin sed

into a 250- c .c . flask,which is then fi l led up to th e

mark Any sulphure tted hydrogen present i s pr e

TREATMENT OF THE GAS-PUR IFY ING AGENTS 109

cipitated by the addition of 1 grm . Of freshly pr epared lead carbonate . After a thorough shaking

,

the l iquid is passed through a folded fi lter , and an

al iquot part of same,in acid solution , i s titrated

with copper sulphate,ferric chloride being used as

indicator .The copper reagent i s prepared as follows : 12

13 grms . of pure Oopper su lphate ar e dissolved in 1

li tre of water , and th e solution is standardized with

,a 0-4 per cen t solution Of pure potassium ferrocyan ide . With th i s object , 50 c .c . of this lattersolution ar e treated , in a beaker , with 5 c .c . Of dilutesulphuric acid Copper sulphate so lution i sn ext al lowed to r un in from a burette un ti l th e application of a strip Of test paper no longer reveal sth e formation of Prussian blue . This test paper i sprepared by allowing one drop of th e test liquid tofal l on to a strip Of absorben t paper ( free from iron ) ,and then letting one drop Of ferric chloride fal lon the paper so that th e edges Of th e two liqu id s

’

coalesce . I n presence Of potassium ferrocyan ide , ablue coloration is produced at th e plan e Of con tact .Since copper ferrocyan ide also reacts with ferricchloride

,care must be taken to see that th e ferric

chloride solution comes in con tact with th e testliquid only .

Anoth er method of ascertain ing th e end poin t ofth e reaction con sist s in filtering 0 1 c .c . Of th e testliquid

, after each application of the copper solution,

and addin g ferric chloride solution t o the fil trate . I f

no blue coloration appears after th e solution has


been observed on wh i te paper for half a minute , thenthe reaction is complete .

A sharp distinction must be made between thesetwo methods of determin ing the end poin t

,the r e

sultingvalues not being iden tical . I n both cases i ti s desirable to repeat the titration ,

adding,in a single

dose, a slightly smaller quan tity of the Oopper solution

than was con sumed in th e first test, and ascertain

ing th e end poin t in the same way as before . I n

these circumstances th e differen ce between'

th e two .

methods i s reduced ; but in any even t the fi ltrationmethod gives higher values than the other . The

standardized copper-sulphate solution ,prepared as

above , corresponds to grm . of

K,Ee (cN ) s o .

I n order to calculate the results to cyanogen compounds other than potassium ferrocyan ide

,the

values Obtained must be multiplied by the followingfactors :

For Cyanogen CN 03696

H ydr ocyan ic ac id,H CN 0 3839

H ydr ofer r ocyan ic acid , H 4Fe (CN )G 05 118

Pr uss ian b lue,Fe 7 (CN )18 06 792.

Dr eschmidt found that the un favourable influenceexerted on the ti tration by the r e- solution of thePrussian blue cannot be avoided en tirely ; and h e

therefore propose s to determine the ferrocyan ide in

th e spen t purifying agen t by mean s Of mercuricoxide . When cyanogen compounds ar e boiled alongwith mercuric oxide , soluble mercuric cyan ide i sformed but since th e pu rifying agen t also con tain s



mark , and after being we ll mixed,the liquid is

fi ltered through a dry fi lter . Of th e fi l trate,100 c .c .

ar e run in to a 400- c .c . flask contain ing 40 c .c . Of

decinormal si lver solut ion and 30 c .c . of a 10 per

cent solution of n i tric acid ( free from chlorine ) . The

cyanogen ,thrown down as si lver cyan ide ,

i s collectedtogether by shaking , and th e flask i s fi l led up to th emark . Th e con ten ts ar e next fi ltered again througha dry fi lter

,and the exce ss Of si lver nitrate in 200 c .c .

of th e fi ltrate i s ti trated back with -normalthiocyanate solution , by the Volhard method

,in pr e

sence of ferric sulphate as indicator . The dif'

erencebetween the number Of c .c . of thiocyanate solutionconsumed and th e 40 c .c . of s ilver nitrate solutiontaken gives th e consumption of decinormal s i lversolution per 1 grm . of air -dry purifying material .One c . c . of decinormal silver solution corres

ponds to °

grm. Of CN ,

0007042 grm . Of K4Fe (CN )6 3H zO ,

0004782 grm . ofFe 7 (ON )18.

A quick method which gives values on ly slightlyhigher than those of Knublauch and Dr eschmidt has

been worked out by Witzeck ,in con sequence of an

exhaustive examination of Fe ld’ s method Of deter

mining cyanogen . According to his proposal , 2 grms .

of th e gas-purifying material s ar e triturated for

about five minutes in a porce lain mortar with 1 c . c.

of a solut ion of ferrous sulphate (containing 27 8 grms .

Of ferrous sulphate per l itre ) and 5 c .c . Of causticsoda (320 grms . per l itre) . I nto this mixture , 30 c .c .

TREATMENT OF THE GAS-PUR IFYING AGENTS 113

of magnesium chloride solution (600 grin s . of MgC l2per l itre) ar e r un by degrees with con tinued stirring

,th e

,

whole being swilled with a large volume

Of hot water into a 200 c .c . retort . I n presence of

30 c . c . of sulphuric acid (of four times the normalstrength ) , th e liberated hydrocyan ic acid i s d istil led over , th e distilla te being collected in 2 -norma lcaustic soda and titrated with decin ormal si lver n itratesolution in presence Of 5 c . c . of i

-normal potassiumiodide solution . One c . c . of dec inormal s i lver solution corresponds to 00 09 5 6 grm . Of Prussian blue .

Th e selling value Of the spen t purifying materialdepends on i ts cyanogen con ten t

,though the amoun t

Of th e other utilizable substan ces presen t must alsobe determined

,for manufacturing reason s . Th e de

termination of the sulphur , sulphuric acid,thio

cyanogen and ammon ia does not differ essen tial lyfrom the methods generally used for th ese substan ces

,

and therefore n eed not be gone in to in de tai l here .

I n determin ing th e sulphur by extracting th e air

dry material with carbon disulphide in the Soxhletapparatus

,the sulphur con ten t can be ascertained

direct,from th e loss in weigh t of th e flask after th e

expulsion of th e so lven t . Gas purifying materials,

however , always con tain smal l quantities of organ icsubstances

,which pass into solution during the ex

traction process . Un less very accurate results ar e

required , i t will be suffi cien t to suffuse th e residuewith e th er , and to pour off th e organ ic substancesthus dissolved along with th ose from t he sulphur . For

accurate determination s , the sulphur must be con

8


verted in to sulphuric acid,by oxidation with potas

sium chlorate or fuming . n i tric acid , and determinedas barium sulphate .

Th e products recovered from the spen t purifyingmaterial ar e : cyanogen

'

compounds,thiocyanogen

compounds,ammon ia and sulphur , or sulphuric acid .

Th e ammonia i s almost en tirely in a state of combination .

The preparation Of cyanogen compounds from th e

spen t purifying materials i s not altogether amongthe simplest of Operations . The large content ofsulphur

,which

,on accoun t of i ts low market value ,

cannot be extracted at a profi t , has to be carriedthrough the wh ole process as bal last , and

,in th e

basic dissociation Of th e materials,favours th e forma

tion Of thiocyanogen—Of course at the expen se of thecyanogen . I n spite

,however

,of th e fact that th e

extraction of sulphur is prescribed in many processes ,it is seldom carried out in practice .

A large number Of methods have been proposedfor th e recovery of th e cyanogen compounds , on lya few of which

,however

,have been adopted into

practice . The most important and th e one a lmostexclusive ly in u se at present is that described inKunheim and Z immermann

’ s German Patent83 . Th e sp en t purifying material i s first l ixiviatedwith water

,to extract the soluble ammon ia salts ,

and is then dried in th e air . The sulphur i srec overed by extraction with carbon disulphide ,

and the residual mass i s in timate ly mixed withgroun d caustic lime and warmed to 40-100

°

C .



ferric hydroxide . The Pruss ian blue is then extractedwith concen trated hydroch loric acid and i s throwndown

,in a pure state , on d ilution with water .

Anoth er poss ible method Of treat ing spent purifying material s consists in converting the cyanogencompounds into thiocyanogen compounds

,with quick

l ime (Marrasses , Ger . Pat . or'

with bary ta or

barium sulphide (HOlbling) , under pres sure . Since ,

however , th e demand for thiocyanogen compoundsis far smal ler than that for cyanogen compounds

,

and can,in fact

,be met by th e compounds already

presen t in th e spen t purifying material s,there i s no

need to go in to th e detail s Of these processes .For th e treatmen t of Spen t purifying material s

there i s a choice Of three systems :

1 . E xtracting th e sulphur with carbon disulphide .

and then treating th e material further as under 2and 3 .

2 . The material i s first freed from th e solubleammon ium thiocyanate and sulphate by lixiviation ,

and th e residue i s dissociated with lime or alkali s .3 . Th e materia l i s treated direct with lime or

alkalis,so as to Obtain cyanogen

,thiocyanogen ,

and

sulphuric acid in the same extract .I n 2 and 3

,th e sulphur con tent (about 30-40 per

cent) of th e material i s carried , as ballast , rightthrough th e process . I t would

,therefore

,from the

ideal standpoin t , be preferable to extract the sulphurfirst ; but in Spite of th e attractiveness of th e idea ,

th e pre liminary extraction of th e sulphur is rare lycarried out

,th e Operation requiring very careful

TREATMENT OF THE GAS-PUR IFYI NG AGENTS 117

supervision , owing to th e high fir e ri sk and in juriousaction of th e solvent (carbon dioxide ) on th e humanorgan i sm .

EL IM INATING THE SULPHUR BY EXTRACTION .

The air -dry spen t purifying material i s first groundin a disin tegrator , so as to pass through a 4 -m .m .

sieve . Th e apparatus used for extracting the sulphur consists of the extr actor , the conden ser , a sti l l ,a tank for th e solven t and a trap for th e separationof water . The cylindrical extractor i s prov ided witha perforated fal se bottom covered with a fi lter cloth

,

on which th e purifying material is spread so as to fi l lthe vesse l

,be ing introduced through a manhole for

this purpose . Th e material i s then covered overwith another fi lter cloth and th e manhole i s closed .

Th e carbon disulphide in the stil l.

is vaporized bymean s of a steam coi l and admitted in to the chargedextractor

,where mos t of i t condenses

,drain ing down

through th e charge and extracting the sulphur , afterwhich it is run through a second pipe back to thestil l . Th e uncondensed carbon disulphide passesaway to the condenser

,where i t condenses in a

water-cooled worm and collects in a rece iver,whence

i t can be led O to th e still as required . Al l the

connections ar e provided with valves . I n conductingthe distillation , a quantity of solven t equal to th eamoun t conden sed in the conden ser i s r un from th e

Storage tank in to th e still . The extraction i s con

tinned un ti l a sample of th e carbon disulphide ,taken

from between the extractor and th e st ill,no longer


leaves any sulphur behind on evapor ation f After al lth e sulphur has been extracted , th e valves ar e set

SO that al l the carbon disulphide vapour coming fromthe st ill passes in to the condenser

,whils t at th e

same time th e supply from th e storage tank to th estil l i s cut Off. I n th i s way the sulphur is freed fromthe solven t , and is drawn 0 wh en mel ted . Steam I S

then blown through th e extraction residue , in order toexpel th e carbon disulphide complete ly .

Th e residual material i s treated,for th e extraction

of th e ammonium sal ts,in exactly the same way as

when th e sulphur is left in .

L IX I V IATING THE PUR IFYING MATER IAL .

I n th e cou rse Of treatment for recovering thecyanogen compounds

,th e usual practice now i s to

extract th e material with water first,the method of

extraction in an apparatus fitted with stirrers,for th e

purpose of Obtain ing a concen trated liquor whichcan be worked up for thiocyanogen compounds , hav:

ing been en tire ly abandon ed in favour of fil terboxes in which the material i s lixiviated systematically . Th e usual dimen sion s Of th e fi lter boxe s ar e

7 feet by 6 feet by 3 feet,and th e holding capaci ty is

about 3 ton s . Th e boxes ar e of iron,or preferably

wood,the bottom be ing of six to seven baulks , ar

ranged at un iform in tervals and provided on th e

upper face with V-shaped grooves,2 inches deep and

6 in ches apart , to allow the liquid to drain away nuimpeded . On the bottom , and at righ t angles tothe timbers , i s a grating of laths (about 15 inches



prin cip le . After leaching th e con tents Of th e firstbox

, th e liquid passes in to the second and there becomes enriched by extracting further quan tities ofsoluble salts

,and so on un t il th e end box is reached .

I n this way the box con tain ing the most exhaustedmaterial rece ives th e fresh water

,whilst th e freshly

charged box is first extracted with th e most coneentrated l iquor

,th e succeeding extractions be ing effected

with progressively weaker liquors , un til , final ly , freshwater comes into action on the n early spen t charge .

As a rule ,eight boxes ar e connected together to form

a battery , so that the material in each is extractede ight times .Assuming

,in the first place

,that al l the boxes ar e

charged with fresh spent material . Fresh water isadmitted in to box NO . 1 ,

and left to stand for abouttwen ty hours

,th e l iquor being then r un Off in to a

collecting basin,and tran sferred thence to box NO . 2

by a pump or in jector . Owing to the fact that acertain quan tity of water is retained by the materialin the first box

,a corresponding amount of fr esh water

must be supplied to NO . 2 . Box NO . 1 i s rechargedwith fresh water . At th e end Of twen ty hours th eliquor from box 2 i s r un Off in to a col lecting basin

,

and at th e same time that from NO . 1 i s dischargedinto another basin . The two liquid s ar e transferredto boxes NOS . 3 and 2 respective ly , and NO . 1 i s r e

charged with fresh water . These Operation s ar e

repeated un ti l the first liquor is discharged from the

e igh th box . NO . 1 box is now disconnected and r e

ceives a fresh charge of spen t pur ifying material ,

TREATMENT OF TH E GAS-PURI FYI NG AGENTS 121

th e l iquor from box 8 i s admitted in to box 1 , and

al l th e other l iquors ar e advanced a stage to corre

spond . Th e l iquor discharged from box 1 after a

further s'

ojourn of twen ty hours therein is almostcomplete ly saturated with soluble salts . I t has a

den sity Of 12-14°

Bé.

,and i s run O

M

in to a collectingtank for further treatmen t

,whilst box NO . 2 now r e

ceives a charge of fresh water . By proceeding inthis way a charge Of liquor can be drawn Off into thecollecting tank each day ,

and one unit of th e batterymust be recharged . With a battery Of th is kind ,24 tons of spent purifying material can be leachedin a week .

TREATING THE L IQUOR .

Th e valuable contents of th e l iquor from th e l ixiviation of th e spen t purifying material consi st Of

ammonium thiocyanate and sulphate . Th e liquorcan be treated direct in a column still of th e kindalready described

,thus recovering the bulk of th e

ammonia contained in the Spen t purifying material .I f

,however , i t be desired to prepare thiocyanates from

th e l iquor , this latter is concentrated in evaporatingpans , and th e two salts ar e separated by fractionalcrystall ization . The sulphate of ammonia i s depositedfirst , and th e bul k of th e thiocyanate is afterwardsrecovered by further concentration and crystallization .

N e ither of th e salts i s as yet in a marketable con

dition . Th e sulphate i s freed from ammon ia in a

column stil l and i s then obtained in a pure state ,whilst th e thiocyanate i s purified by recrystall ization .

The thiocyanate can also be recovered from the

122 COAL GAS B Y—PRODUCTS

mother liquor Of the sulphate of ammon ia,as cuprous

thiocyanate , by treatmen t with copper sulphate and

sulphurous acid , and is squeezed in the fi lter press .Further particulars on th e treatment of th e crudesalt and th e copper salt wil l be given later .

TREATING TH E EXTRAOTED MATER IAL .

The l ixiviated puri fying material i s next subjectedto' further treatmen t for th e recovery Of cyanogen

,

which is present in th e form of in soluble fer r ocyanide . Treatment wi th alkalis or l ime converts it intothe soluble alkali or calcium ferrocyan ide compound .

The tran sformation takes place in th e cold,but is

acce lerated and rendered more complete by warming .

I n practice ,of course

,lime alone —or perhaps soda

i s used as the dissociating agent,th e other alkalis

be ing too expen sive . Th e process i s carried on

ei ther in vessel s provided with mechanical stirrersor in fi lter boxes .At the first glance

,th e former method would seem

th e more suitable ,th e Object being attained more

quickly by constant stirring , wh i l st at th e same timea smaller excess of reagen t i s su

'

icient . This treatment , however . resul ts in a portion of the materialbeing converted into a fine Sludge

,which cannot be

separated in to liquor and res idue ,e ither by settling

or by suction fi lters , fi lter presses being necessary .

Moreover , th e homogeneity of the material i s destroyed

,nearly 7

171 be ing still in

‘

the condition ofcoarse granule s and in th ese circumstances th efi l ter press i s very liable to be choked up . To pr e



To start th e apparatus , th e cylinder is charged witha corresponding quan tity of weak l iquor, and the

stirrers ar e set in motion,the material to be treated

being then in troduced through the manhole,and

th e steam turned on . The dissociation takes two tothree hours , according to th e quan tity treated . At

this stage th e mas s i s diluted with weak liquor,the

stirrers ar e stopped,and the whole is left at rest for

about half an hour,to allow th e coarser material to

settle down . The Sludge i s next drawn O into a

fi lter press by a siphon , which extends down to th eleve l Of th e coarse material ; and in th i s pre ss th ematerial i s washed un ti l th e washings no longer exb ibit any traces of cyanogen . A sufficien t quan t ityOf the weak liquor to dissociate a fresh charge i s introduced into the cylinder

,and a fresh quantity of

spent purifying material i s t reated . When,in this

way , a u icient amoun t of coarse materia l has ao

cumu lat

s

ed in the cylinder i t i s drawn 0'

throughth e cock and completely extracted in the fi lter press .The various liquors ar e collected in a tank . According to the dissociating agent used , they containsodium ferrocyan ide or calcium ferrocyanide .

B Ossner , in his work on th e utilization of spen t

gas purifying material s,reports on a number Of ex

per iments made in th e dissociation of the materialwith lime and soda

,th emethod adopted being similar

to that described above . Th e lime was used in th eform Of slaked l ime contain ing about 50 per cen t ofCaO

,11 parts Of CaO being added to every 100

parts of matei ial in order to provide for the insol

TREATMENT OF THE GAS-PUR IFYING AGENTS 125

uble sulphate s in th e lixiviated mass . The actualconsumption of lime ranged from one and a half tothree times the theoretical quan tity . At th e ordinarytemperature

, although a threefold quan tity of lime was

used,the dissociation amounted to on ly 66 per cent ,

corresponding to th e formula K4Fe (CN ) 6 3H z

O butwas increased to 80 per cen t cn rais ing th e temperature to 5 5 C . ( 13 1

°

Further rises in temperaturegreatly facil itated th e formation Of th iocyanogencompounds

,a l l the requisite compon en ts Of which

( lime , cyanogen and sulphur) ar e presen t in th e

material . To increase the dissoc iation at the tem

peratur e mentioned, a mixture of l ime and Soda was

added towards the end of the Operat ion ,the addition

of lime being natural ly reduced accordingly ; and in

thi s way th e dissoc iation was increased to 96 per

cent . Th e addition Of soda converts the calcium

ferrocyan ide into Na2 6 ;CaFe (CN ) but a s u cien t

amount Of soda must be u sed to dissociate th e

ferrocyanogen as wel l . A very important factor influencing the success Of the treatmen t is not to workwi th very large charges ,

As already men tioned,the stirring process has

now been superseded by th e fi l ter -box method,

because it enables a dissociation of 8 7 per cen t tobe Obtained with lime alone

,without th e u se Of

complicated apparatus . Th e fi lter boxes ar e Of

exactly th e same pattern as those used for lixiv iating th e spen t purifying material ; and th e processi s carried out in just th e same way . After th eOperation , the material i s left to drain for several


days in th e boxes,and i s then spread out to dry on

a cemen t or asphal ted floor and turned over fr equen tly with a Shovel . As soon as i t no longer“ bal ls wh en squeezed , i t i s air -dry , whereupon a

definite quan tity of powdered lime i s strewn over it ,and th e two ar e thorough ly mixed with the shovel .Th e amoun t of lime thus added is equal to th equan tity of potassium ferrocyanide presen t . Th e

mixture is screen ed in a 4 mm . sieve , and th e

residual lumps ar e al so crushed and screened . Th ismixture is again placed in th e fi lter boxes , su

M

icient

water being added to cover th e mass . The leaching process i s precisely th e same as in th e originall ixiviation in th e fi lter -box bat tery . Th e resultingliquor has a density Of 12 -14

°

B é. and contain s120 gu ns . of K

4Fe (CN ) 6 . 3H

zO per l itre . I rre

spective of th e original con ten t of potassium ferrocyanide

, per cent of that salt is left behindin the residue ,

the percen tage referring to th e ma s sin th e condition in which it was , as regardsmoisture , previous to th e addition of th e lime .

With th e fi lter -box method th e cyanogen Obtainedin th e l iquor is in the form of calcium ferrocyan ideexclusive ly . The further treatmen t of th e liquorwill be described later , in connection with that ofth e l iquor Obtained from the cyanogen sludge .

The third system of treatment , by di s sociationwithout previous lixiviation

,i s applied when the

spent purifying material is very low in Soluble am

monium salt s ; and the operation is carried on inclosed fi lter boxes

,in order to prevent inconvenien ce


CHAPTER VI I .

TREAT I NG THE CYANOGEN SLUDGE.

TH IS operation is comparatively simple , since one

has on ly to deal with substances of known composition

,and the work is rendered easier by th e

absence of sulphur .Up to th e presen t , only th e meth ods of Fou lis

and B ueb have to be considered in the absorption ofcyanogen by the wet proce ss in the course of gaspurification .

Accord ing to the Fou lis method,the washing

liquor con tains Prussian blue , potassium fer r ofer r i

cyanide and ammon ium fer ro fer r icyan ide , togetherwith soluble cyanogen compounds . The sludge i ssqueezed in th e fi lter press

,and th e ammon ia in th e

clear filtrate is expe lled in a column still . Th e

residual l iquor from the latter con tain s calciumferrocyanide in solution The residue from th e

filter is d issociated with caustic lime in an apparatusfi tted with stirrers , and th e resulting clear liquor isun ited with that from th e column sti ll

,to be treated

for recovering ferrocyan ide salt s . According to theB ue

'

b method , th e soluble portion of th e sludge con

( 128)

TREATI NG THE CYANOGEN SLUDGE 129

t t ins ammonium ferrocyanide , whilst the insolubleportion corresponds to the formul a

2NH4 (CN ) Fe (CN ) 2 (Hand) ,

or (Fe ld) .

The cyanogen Of th e soluble ammon ium ferrocyan ide is converted into the insoluble form by boiling the sludge in closed iron vessel s

,fitted wi th

condensing apparatus . I n this process all the freeammonia i s liberated , and is worked up in th e

manner already described . The s ludge is nextsqueezed in fi lter presses

,and the sulphate of am

monia con tained in th e filtrate i s worked up as such,

Whils t the p ress cakes ar e dissociated with lime in a

sti rrer apparatus , the resulting calcium ferrocyanidel iquor being subjected to further treatmen t .

CHAPTER VI I I .

TREATI NG TH E CRUDE LI QUORS .

THE crude l iquors from th e dissociation processcontain a variable mixture Of sal ine matters , according to th e previous treatmen t Of th e material .When the prel iminary lixiviat ion has been omitted ,the material will contain calcium thiocyanate and

gypsum,in addition to the cyanogen compounds

,

whereas i f dissociated with caustic soda and lime ,the hydroferrocyanic acid will be in combinationwith calcium ,

sodium , and some times ammonium °

as wel l . I rrespective of the prel iminary treatment ,this acid must be separated from the other constituents of the l iquor , by precipi tation or crystal lizat ion

,three sys tems being available

1 . Precipitation with iron salts , as a blue pr ecipitate which varies in composition and i s commonlytermed “ blue ”

.

2 . Precip itation , as a double calcium-ammoniumsal t , by means of ammonium salts . "

3 . Precipitation , with potassium chloride,

as a

double,calcium-potass ium salt .

(130)



and the resulting pulsating action Of the pump isliable to tear the filter cloths

,so that the use of a

pressure vessel is preferable . The washing,too

,i s

a protracted Operation and i s always attended withloss . The resulting pres s cakes , wh ich containabout 30 per cent of K4

Fe (CN) . SH2O ar e decom

posed with caustic potash Or soda,in a stirrer

apparatus,the reaction be ing expressed by the

equations :

Na2FeFe (CN)

6+ 2NaOH Na

4Fe (CN ) 6+ Fe (OH )

Fe2Fe (CN ) 4NaOH Na

4) 6Fe (CN 2Fe (OH )

2

Th e prec ipitated ferrous hydroxide presents th eunwe lcome feature of cau sing di cu lties in respectOf sett ling down and fi ltration , and necessitates r e

course to the fi l ter press again,in which connection

th e protracted washing Of the press cakes —which ,moreover , yield a very weak liquor—is highly inconv enien t, the further concentration of the liquor taking up much time and pat ience . For thesereasons the method is now seldom used

,unless i t be

desired to extract further smal l quantities of cyanogenfrom th e spent l iquors .The Kunhe im and Z immermann proc ess accom

plish es th e same Obj ect in a much simpler and

quicker way . I n presence of alkal i or ammoniumsal ts , in the warm ,

calc ium ferrocyanide furnishes insoluble double salts , according to the equations

aNH,Oi

Ca2Fe (CN ) 6 2K01 = OAOI

,

TREATI NG THE ORUDE LI QUORS

2 . PRE C IP ITATION W ITH AMMON IUM SALTS .

Th e reagent con sists of a solution Of ammoniumchloride

,which

,according to the character of the pr e

l iminary dissociation proces s , i s e ither added p er 36,

or el se the l iquor from the fi lter boxes is manipu latedin Such a way that it contains su

“

cient ammon ia tocarry out th e reaction . This lat ter will general ly bethe case when th e spent purifying material hasnot been lixiviated before dissociation . I n these circumstances , su

M

icient hydrochloric acid i s added toneutral ize th e ammon ia

,but if th e material has been

previously l ixiviated , a suM

cient amoun t of un lixiviatedmaterial i s added , for the dissociation treatment , tointroduce sufficient ammon ia to precipitate th e

double salt from th e whole of the crude l iquor . The

precipitation is effected in apparatus provided withmechan ical s tirrers . Th e liquor is heated by directs team

,and the prec ipitation of the double sal t begins

when th e temperature reaches 7 5 °

C . When th e deposition is completed

,the steam is turn ed Off and

the stirrers ar e stopped,the clear liquor being drawn

OM

when th e sal t has s ettled down . This latter i srepeatedly washed with water

,by decantat ion

,and is

final ly put through the fi l ter press . I t may occasional ly be profitable to precipi tate th e cyanogen ,

present in the washings and mother l iquor , in th e

form of “ blue ”. The precipitated doub le sal t

i s a white substance with a bluish tinge , and i t may

e ither be reconverted in to th e calcium sal t,or e lse

transformed direct in to potassium ferrocyan ide . I n

134 COAL GAs Biz-PRODUCTS

th e case of very good double salt , a marketable ar ticlecan be produced direct ; but in other cases th e cal«

cium sal t has to be prepared as the intermediateproduct . For this purpose a suitable quan tity ofl ime is added to the solution of th e double salt , ina stirrer apparatus of the kind already described , theliberated ammonia being worked up into one or otherof the preparations referred to earlier . The reactioncorresponds to th e equation :

CaO Ca2Fe (CN) 6 2NH 3

H20 .

When al l the ammonia has been driven O the r e

su l ting l iquor is concen trated to 20-21°

Bé. and putaside to crystall ize

,the black sludge formed during con

centration being removed in a fi lter press . Th e

calcium ferrocyan i de i s treated in exactly th e sameway as the crude liquor precipitated with potassiumchloride . As already sta ted , the ammonium doublesal t can be converted direct in to potassium ferrocyanide

,for which purpose a corresponding quantity

Of potassium carbonate i s placed in the s tirrer ap

paratu s,together with th e requisite amount Of l ime .

Th e reaction corresponds to th e equation :

CaO 2K2CO

3

K4Fe (CN

6) 2CaCO3 H2O 2NH

3.

After th e expulsion Of the ammonia ,th e l iquor is con

centrated to 3 1° Bé. ,filtered and set to crystal lize .

3 . PREC IP ITATION W ITH POTASS IUM SALTS .

The best method Of Obtaining good salts from th e

crude liquors is through the potassium double salt .



sium ferrocyanide by boiling it with potassium car

bonate,in accordance with th e reaction :

CaK,Fe (CN ) 6 K

,OO3 K

,Fe (CN ) 6

After the calcium carbonate has sett led down , theclear liquor (density 27

°

B C.) i s concentrated to 303 1

°

B C. in iron pans,and i s then set to crystal l ize ,

whils t stil l hot , in pans , about 4&feet deep and 3

fee t across,which ar e lagged with wood to prevent

loss of heat . Across the top of each pan a numberOf rods ar e laid

,to which ar e attached Strings lead

ing nearly to th e bottom of th e vesse l . The crystalscollect in clusters on these strings . Th e pan s mustbe kept free from vibration during the crystal lizingprocess , which takes about a fortnight to comple te .

The crystal s ar e broken up and whizzed , th e motherliquor being returned to the crystallizing pans un til i ti s so rich in potassium sulphate that this salt beginsto crystallize

‘

Ou t first,whereupon th e liquors ar e

placed"

aside and concentrated separately . The r e

su lting crystal s stil l contain about 60-80 per cent ofK,Ee (CN) 6 SH

,O .

CHAPTER IX .

TH E TREATMENT OF CRUDE AMMON I UM TH I OCY

ANATE AND CUPROUS TH I OCYANATE.

THE crude ammon ium thiocyanate Obtained in th e

l ixiviat ion of Spen t purifying material i s dis solved inwater , and the heavy metal s ar e thrown down , as

sulph ides , by means Of barium sulphide , th e sulphuricacid present precipitating th e barium at the same

time . The addition of barium sulphide i s continueduntil th e fi l trate no longer gives a precipitate w iththe same reagen t . Th e mixture i s squeezed in th e

fi lter press , after which th e l iquor is concen trated to20-25

°

Bé. and left to crystal l ize . Th e re sultingsalt is not a marketable commodity

,but has to be

recrystal lized . This is done by dissolving it,throw

ing down any heavy me tals , sti l l presen t , with am

monium sulphide,drawing O

M

th e clear liquor andconcentrating it to 18 -20

°

Bé. Th e crystals separating out as the solution cool s ar e removed from th e

mother l iquor,whizzed and dried . Th e product i s a

pure,wh i te ammon ium sal t .

I n connexion with th e lixiviation Of the purifyingmaterials i t has been men tioned that the thiocyanogen in th e l iquor can al so be thrown down by

(137)


copper sulphate . This product , cuprous thiocyanate ,serves as th e raw material for other thiocyanates .Treated with barium sulphide solution in a stirrerapparatus , i t i s decomposed as follows

2CuCNS B aS B a (CNS) 2 CazS .

Th e Copper sulphide i s separated by pressing,

Whilst the barium thiocyanate l iquor is passedthrough a charcoal fi lter , concen trated to about 60

°

Bé.,and placed in iron pan s to crystal lize . Th e

sal t is separated from the mother liquor by whizzing ,and forms a marketable product .To prepare potassium thiocyanate , th e purified

barium thiocyanate solution is treated with a corresponding amoun t Of potassium sulphate , separatedfrom the precipitated barium sulphate by pressing ,and the liquor is concen trated to about 40

°- B e.

The salt Obtained on crystal l ization is purified byrecrystallizing .


COAL GAs BY-PRODUCTS

current of washed chlorine is passed through a cold10 per cen t solution un ti l th e whole of the ferrocyan ide has been oxidized . Th e end point of th edecomposition must be carefully watched for , ordi ffi culties wil l occur during crystallization . I f th e

oxidation be insufficient,the resulting salt wil l be con

taminated with ferrocyanide ; whilst if carried toofar

,Prus sian green will be formed

,which adheres

to the product with equal tenacity . When oxidationis complete

,the solution is concen trated to 27

°

B é

(hot) , and put aside to crystallize , an Operation takingabout five days . Th e mothe r liquor is furtherconcen trated to 29

°

B e. (hot ) . The crystal s fromth e mother l iquor ar e con taminated with potassium chloride; and this sal t serves for con centratinga newly oxidized patch . A number of motherliquors from th e second crystallization ar e concen

trated unti l th e potassium chloride separates out ,the bulk of this salt being washed out of the crystalswith cold water . I n this method of working

,a yield

of 88 -90 per cent is Obtained .

The oxidation of potassium ferrocyanide by meansOf peroxides was in troduced into practice bySchOnbein . When the ferrocyan ide i s treated , at

boil ing temperature,with lead peroxide

,i t is oxi

dized , lead oxide and caustic potash be ing alsoformed . These two compounds ar e converted intocarbonates by the introduction of carbon dioxide , thelead carbonate being precipitated . Th e potassiumferricyanide and potassium carbonate can be easilyseparated by fractional crystal li zation . The lead

POTASSI UM FERRI CYAN I DE

carbonate is reconverted into the peroxide,by mean s

of bleaching powder .A modification of this p rocess has been brought

forward by Kassner,who replaces the lead p eroxide

by calcium plumbate and carbon dioxide . Th e de

composition proceeds ac cording to the equation :

2K4Fe (CN ) Ca

2PbO

,4CO

Z

2CaCO3

PbCO3 wo

g.

The potassium carbonate left in solution is utilizedby oxidiz ing an equivalent amount of ferrocyan idewithout addition of carbon dioxide ,

and adding theproduct to this Solution , whereupon potassium ferricyanide and calcium carbonate ar e formed . Th e

latter settles down , and the clear supernatant liquor

is Siphoned O and concen trated to crystall izationpoint . Since th e calc ium plumbate i s prepared bycalcin ing lead oxide and calcium carbonate

,it serves

to some extent as a carrier of atmospheric oxygen .

Th e method which is probably most widely usedat presen t for preparing ferricyanide i s that ofOxidation by e lectrolysis . I n th e e lectroly sis Of

water , the oxygen is separated at th e anode , and

the hydrogen at th e cathode and i t i s th is nascen toxygen which is util ized for oxidiz ing potassiumferrocyanide . The reactions ar e expressed by thefollowing equations

Hzo H

2O .

O 2K3Fe (CN ) 6 ‘ 1‘ K2

0

K20 H

2O 2KOH .

2K4Fe (CN ) 6 2H

20 2K

3FC (CN ) 6 2KC l—1 + H 2’


The potassium ferricyanide i s deposited , in a purestate , on the anode

,the yield amounting to 9 5 per

cent and over . A number Of patents ar e based onthis process (Buschweiler , Petrie , Dubosq ,The electrolysis is suspended as soon as all the

ferrocyanide has been oxidized , a condition whichis recognized by the circumstance that th e l iquor nolonger decolorizes potassium permanganate solution .

According to the process of the Deutsche Goldund Silber scheideanstalt (Ger . Pat . a mixture of potassium ferrocyanide and calcium ferrocyanide is oxidized . The u se of calc ium salts , inaddition to potassium salts , in the decomposit ionscorresponding to the reaction , is s tated to ensurea purer product be ing Obtained

,since the whole

of th e potassium combines with th e fer‘

ricyanic acid ,and any lime that may be left behind in solutioncan be completely precipitated with carbon dioxide .

The reactions ar e expressed by the equations

3K4Fe (CN ) 6 Ca

2Fe (CN ) 6 C

2

4K3Fe (CN ) 6 2CaO ; 2CaO 2CC

22CaCO

3.

The u se of ammonium and sodium persulphatesfor oxidat ion is dealt with in Beck ’s German Patents

and the reaction corresponding toth e equation :

2K4Fe (CN ) 6 (

‘

NH s,o82K

3Fe (CN )6 2 (NH 4)KSO4

The potassium ferrocyanide , which is dissolvedin water is oxidized with ammonium per

sulphate at 60°

C 270 parts by we ight of ammo

4h


CHAPTER XI .

TH E CYANOGEN PiGMENTs .

THE cyanogen pigmen ts con sist of complex compounds Of iron salts

i

and hydr ofer r i or hydr ofer r ocyan ic acid . Th e chief represen tatives of th e series ,which ar e met with in commerce as Prussian blue

,

Berlin blue , and Pari s blue,have the formula

,

Chem ical ly speaking,they ar e identical , d iffering

only in their degree of purity . Paris blue is th epurest form . I t has an intense ly blue colour and

a peculiar Coppery metall i c lustre . Th e othermembers : Prussian blue , Berl in blue and mineralblue

, ar e prepared from less pure salts and,in

addition to contain ing such impurities as gypsumand carbonate , ar e adulterated with variable proportions of alumina,

chalk,starch and even heavy

spar . These substances naturally render th e colourcorrespondingly paler , and also impair the bronzelustre .

There ar e two methods of making Paris blue . I n

the on e , a solution of pure potassium ferrocyanidei s treated with ferric salts , thus forming a precipitateof pure Paris blue ; whilst in the other , the pr e

(144)

THE CYANOGEN PI GMENTS 145

cipitation i s e"

ected with ferrous salts,which ar e

cheaper , and th e pale blue to dirty green precipitatei s oxid ized afterwards . The former method natural lyfurn i shes the purer product .A solution of ferric n i trate i s added to one of

potassium ferrocyanide un til a sample no longergives any further precipitate with th e n i tratesolution . The ferri- ferrocyan id

‘

e thus formed se

parates as a completely in soluble substan ce and

settles down . Th e supernatan t l iquid i s siphonedo

”

,and the prec ipitate is wash ed with water

,by

decantation , un til all the potassium chloride has

been extracted . I t i s n ext pressed,while still moist

,

cut up in to cubes and dried . The firs t stage ofdrying is conducted at air temperature or up to30

°

C . (86°

and i t i s only when the productis air -dry that th e drying is fin ished off at 100

°

C

(212°

whereupon the copper-r ed (“ bron ze

metallic lustre,characteristic of th e pure article ,

develops .I n the preparation with ferrous salts

,fol lowed by

oxidation , ferrous sulphate i s employed in practice .

The following may be given as the most suitableproportion s : ferrous sulphate 9 parts by weight ;sulphuric acid (60

°

Bé.) 15 parts (dissolved in 100

parts of water) potassium ferrocyan ide (yell ow prussiate) , 10 parts , dissolved in 100 parts of water .

The addition of sulphuric acid is in tended topreven t th e precipitation of iron carbonate by thecarbonic acid in th e water . Th e two solution s ar epoured in to a wooden vat

,on ly a sl ight excess of

10


the ferrous salt being presen t . Th e l iquid shouldbe kept con stan tly s tirred during th e pouringprocess . Th e resulting white precipitate , whichalways has a slight bluish tint due to small quanti=

ties of ferric sal t , is oxidized with 20 parts of nitricacid added in small quantities at a time ,steam being admitted simultaneously . Th e heatingis continued unti l ‘ no more nitrous fumes can be

observed . I n this way the precipitate i s oxidizedin a very short time . The Paris blue i s allowed tosubside and

, after th e clear supernatant l iquid hasbeen drawn off

,i s washed with water . Th e sub

sequen t treatment of th e precipitate is identical withthat described above .

H och st’

aLtter employs bleaching powder and hydrochloric acid as the oxidiz ing agent . I n thesecircumstances h e has to start with ferrous chlor ide ,and dispen se with the u se of sulphuric acid

,since

otherwi se th e fin ished product would be contamin

ated with gypsum . Any oxidizing agen t can be

used for turn ing th e white precipitate blue , man

ganese chloride being a highly suitable means .After separation from the solution

,th e precipitate

is treated with a solut ion of manganese chloride inexcess ; and as soon as the colour of the productattain s its maximum inten sity

, the oxidation iscomplete .

Berlin blue differs from Paris blue sole ly byreason of impurities

,in consequence of which it i s

inferior in “ bronze I n stead of working withpure salts

,a crude salt , such as that obtained in


148 GOAL GAS BY-PRODUCTS

proportion s being given by Brucke : Potassiumferrocyanide 21 70 parts , dissolved in partsof water and treated gradual ly with a solution of100 parts of ferric chloride in 1000 of water ,Th e iron solution is mixed with twice i ts volume ofa saturated solution of Glauber salt (sodium sulphate) . The resulting precipitate i s fi ltered off, andi s washed with water so long as th e washingsexhibit a bluish tinge . The residue is then dried

,

and i s sold in th e form of powder . This blue,

which is . chemically the same as Berl in blue,i s

comple tely soluble in water .Guignet uti l izes the solubili ty of Berlin blue in

oxal ic acid , for preparing a soluble blue . A saturated solution of oxal ic acid i s shaken up with a largeexcess of Berlin blue in paste form , and filtered

,

th e solution be ing then left to itsel f for two months,

durin g which interval th e dissolved Berlin bluegradually settles down , leaving the solution as c learas water . Th e blue obtained in this way is al sosoluble in water . I n addition to oxalic acid , tartaricacid and molybdic acid have thefaculty of d issolvingBerlin blue .

Apart from Berlin blue and its varieties , men

tion may be made of th e copper salt of potassiumferrocyanide , which i s of a brown colour , and is met

with in commerce as

'

Hatche t brown . I t i s pr epared by precipitating a solution of potassium ferrocyan ide with copper sulphate , the shade of th e

product varying in accordance with the excess ofcopper sulphate used .

CHAPTER XI I .

SULPHUR AND SULPHURI C ACI D .

I F i t be desired to recover sulphur , as such,from

th e spent gas -purifying materials,this is preferably

efiected before th e said material s ar e treated for thepreparation of cyanogen compounds . The mannerof extracting th e sulphur has already been dealtwith

,carbon disulphide being the only solvent u sed .

Th e process is exactly Similar to that used in theextraction of fat from bones , and there i s thereforeno need to go into further details .I n the main , the sulphur from spent purifying

material is transformed in to sulphuric acid byroasting , th e material treated in this way being , ofcourse

,such as has previously been freed from the

other valuable constituents . The lixiviated and

dissociated material chiefly con tain s ferric hydroxideor oxide

,ferrous hydroxide , sulphur and lime ( from

the dissociation treatmen t) , in addition to th e substances ( sawdust , etc .) required for loosening th ematerial and facil itating the passage of th e gas to bepurified . I n th e roasting process

, the ferric oxideremains behind , and th e sulphur is l iberated as

sulphur dioxide . Th e roasting furnaces do not

(149)


differ essen tial ly from those used for pyrites and

other sulphur ore s . The entire process of makingsul phuric acid from spent gas-purifying materialsdoes not entai l th e u se of any typical specialappliances , and therefore i t is su

'

icient here merelyto mention that sulphuric acid , al so

,is one of the

by-products of the manufacture of coal gas .

F IN IS .


152

B urme iste r Wa in on separ at ingwater from gas tar , 40.

CALC IUM fer rocyanide , 122 , 125 ,129, 134-6.

Calor imeter , 24 , 25 .

Cannel coal , yie ld of tar , 34.

Car bon ,in coal , 3 .

coke , 23 .

determination of , in gas tar ,

37 -9.

d ioxide , absorption of, by gas

l iquor , 70.

e l iminating in ammon iamanufactur e , 86-8 .

from gas l iquor , 7 1 .

in water gas , 29 .

separ ator , 68 -72 , 7 7 -9 .

monoxide in water gas , 29 .

Carbonaceous matter in gas tar , 35 .

Carpenter ’ s gas pur i fying pr ocess ,20.

Ch lor ine for oxid iz ing fer rocyanide , 139.

Coals,chem ical compos ition of , 3 .

Coke , 23 -9 .

br eaker , 26, 27 .

br eeze,26.

chem ica l compos ition of, 23 .

fragi l i ty of, 23 .

h eating value of , 23 -5 .

phys ical proper ties of,23 .

yield of, fr om coal , 3 .

Column sti l ls for gas l iquor , 606.

Condenser ( atmosph er ic ) ,l iquor from , 7 .

cel lu lar , 79 , 80.

r efiux , 66, 67 .

Copper -potass iumide , 148 .

Copper r eagent for determin ingfer rocyanogen , 109 .

Creosote o i ls in gas tar , 44 , 49 .

Cuprous th iocyanate ,t reatment

of, 137 , 138 .

gas

f e r r o c y a n

COAL GAS BY-PRODUCTS

DEUTSCHE Continental Gas Gese l lschaft method of separatingwater from gas tar , 39, 40.

Gold Silber scheide Anstaltfer r icyan ide process , 142 .

Disti l lation plant , exper imenta l , 2 .

temperatur e of coal , 2 .

Donat Ornstein’

s Pr uss ian bluepr ocess , 115 .

Bor r ite stone fr om gas tar , 42 .

Drehschmidt on determ ination offer r ocyanogen , 110, 111 .

Du long’

s calor ific value formu la ,

24 .

E LECTRODES , r etor t graph ite , 31 ,32 .

E lectrolytic pr eparation of fer r icyan ide , 141 , 142 .

Engl ish coals , compos it ion of,3 .

gas tar fr om ,35 , 43 .

FE LD’S gas pur ification process , 19 ,20.

su lpha te of ammon ia pr ocess ,102-4 .

Fe ldmann-Pintsch ammon ia plant,86-8 .

gas l iquor separator , 71 , 74 ,7 7 -9 .

Fe r r ic oxide as gas pur ifier , 9 , 10,

13 .

Fer r ocyan ides , r ecovery of,114

29 , 141, 142 .

Fer rocyanogen , determination of,

105 -13 .

Cyanogen in coa l gas , 3 .

compounds , pr epar ing fr omspent pur i fying mater ials ,114 -27 .

r emoval of, 7 -21.

sludge , 15 -8 .

tr eating, 128 -9 .

r ecovery of, 116, 122-6.

pigments , 144-8 .

I NDEX

Ferr ous ch lor ide as gas pur ifier14 .

salts as gas pur ifier s , 19 .

su lphate as pur i fying agent ,16, 17 .

Foulis method of tr eating cyan

ogen s ludge ,128 .

-process of hydrocyan ic acidr ecovery, 13 , 14 .

Fr anke’

s gas l iquor sti l l , 58 , 59 .

GAS , crude , compos i tion of,15 .

i lluminat ing, from gas tar , 42 .

l iquor , 53, 104 .

absorpt ion of carbon dioxideby , 70.

ammon ia in , 54 , 55 .

composit ion of, 6-9, 5 3 .

concentrated , 74-81 .

concentrat ing, 5 6, 57 .

distil lat ion of, 5 7 -74 .

from r etor t s , compos it ionof, 7 , 8 .

preh eater for , 65 .

separator s for , 74-81 .

test ing, 5 4-5 .

y ield of, 3 .

pur ificat ion of, 4 -21 .

pur ify ing agents , su lphur ic acidfrom ,

140, 150. S ee

a lsoPur ify ingMater ials .

tr eatment of, 105 -27 .

value of spent , 113 .

tar , 33-52 .

ar tificial stone from, 42 .

as paint, 41 .

compos ition of, 34 , 36.

distil l ing, 43-52.

fr actionating,39 .

i l lum inat ing gas from ,42.

influence of r etor ts on , 35 ,36.

oi ls in , 35 , 36, 43 .

pitch in , 35 , 43, 44 .

phys ical proper ties , 34 , 35 .

sampling, 36.

153

HATCHE’

I‘ br own ,

148 .

Heat ing value of cok e , 23-5 .

gas tar , 37 .

water gas , 29 .

H ir zel’

s gas tar stil l , 50, 5 1 .

Hoch statter’s Par i s blue process ,

146.

Hydr au l ic main ,4 .

gas , l i quor from, 7 .

Hydrocyanic ac id in crude gas , 15 .

r emoval of, 7 -21 .

Hydrogen , in coal,3 .

cok e,23 .

water gas , 29 .

IRON salts , tr eating waste l iquorwith , 131 , 132 .

th ionate pr ocess for su lphate ofammon ia

,103.

KASSNER’

S process for oxidi z ingfer rocyan ide , 141 .

Klonne method of separat ingwater from gas tar , 40.

Knoblauch pr ocess of cyanogen r e

covery ,12

,13 .

determining fer rocyanogen , 107 .

Koh ler on test ing gas tar , 38 , 39 .

Koningh ,De, process for determin

ing fer r ocyanogen ,106.

Kopper ’

s gas l iquor st i l l , 64 -6.

Kramer Spi lker on testing gastar , 39 .

Kr ey’s tar di stil lation process , 50.

$6

Gas tar , separatingwater from, 39

41.

specific gravi ty of, 38 .

testing, 36-39 .

yield from gas tar , 35 .

per ton of coal , 3 .

Gr aph ite , r etor t , 30-2 .

Gruneberg, T ieftrunk Bube ’

s

ammon ia plant,84-6.

Guignet’

s soluble blue , 148 .

154

Kunh eim Z immermann’s fer ro

cyan ide process , 114 ,115 .

process for t reat ing waste

l iquor , 132 .

LAMI NG’S pu r i fy ingmater ial , 9.

Lennard’s tar d ist i l ling process ,

5 1, 52.

Leybold Moldenhauer processfor determin ing ferrocyanogen ,

106.

Lime , m i lk of, in tr eat ing gas

l i quor , 5 7 , 5 8 , 60-5 , 72, 73.

for pur i fyinggas , 8 , 9 .

testing, 5 5 .

washer for ammon ia plant , 84 ,85 .

L i quor , waste treatment of, 130

7 .

Lix iviation plant for spent pur i fyingmater ials, 118 , 121.

MAGNES IUM salts as gas pur ifier s20.

COAL GAS BY-PRODUCTS

Mar rasses’

th iocyanogen pr ocess ,116.

NAPHTHALENE in coal tar,34 , 43 .

N itrogen in coal , 3 .

coke , 23.

water gas , 29.

O I L in gas tar , 35 , 36, 43 .

h eavy in gas tar , 35 , 43 .

l igh t in gas tar , 35 , 43 .

med ium in gas tar , 35 , 43.

‘Opitz Klotz gas tar sti l l , 49 .

O xygen ,in coal , 3 .

coke , 23 .

water gas , 29 .

PAINT , gas tar , 41 .

Par is b lue , 144-6.

RE SPI ER’S gas tar st i l l , 47 .

Rispl er on disti l l ing gas tar , 48 .

Roofing fe lt, gas tar , 41 , 42 .

Rosenk ranz ammon ia absorber ,96.

Per oxides for oxid iz ing fer rocyan Rutger swerk e method of separ atide , 140, 141 . ing water from gas tar , 41 .

Per sulphates for oxidiz ing fer rocyan ide , 142 .

Ph enol in coal tar , 34 , 43 .

Pintsch concentr ator for gas l iquor ,7 4-81 .

process for l i quefied ammonia ,89 , 90.

su lphate of ammon ia plant , 926.

Pi tch in gas tar , 35 , 43 , 44 .

Polysu lph ides as gas pur ifier s, 20.

Polythionate process for su lphateof ammon ia , 103-4 .

Potass ium fer r icyan ide , p repar at ion of, 139-43 .

fer rocyan i de , conver t ing intofer r icyan ide , 139-143.

r ecovery of, 114 , 115 , 125 ,

126, 134 , 136.

sa lts , tr eat ing waste l iqour

with , 134-6.

th iocyanate , pr eparat ion of,138 .

Pruss ian b lue , 107 , 109, 110,144

8 .

in cyanogen S ludge , 15 .

pr eparation of , 131 , 132 .

r ecovery of, 115 .

gr een , 140.

Pur ification , gas , 4-21 .

dry process , 5 -12 .

wet pr oces s , 4 -8 .

Pur i fy ing boxes , 5 .

mater ials , 9-21 .

absorbent capacity of,11 .

r egenerating, 5 , 9 . See a lso

Gas Pur ifyingAgents.

Pyr id in in coal tar , 34 .


S H A L E O I L S A N D T R

W . SCH E ITHAUER.

TRANSLATED FROM TH E GERMAN .

Demy 8vo . 7 5 I llustrat ions . 200 Pages.

Pr ice 8 3 . 6d . net (Post Fr ee , 8s . I od . Home ; gs . Ab road) .CAS H W ITH ORDE R

Contents of this Wor k sent Post F r ee

on appl ication to the Publ isher s

SCOTT ,GREENWOOD SON ,

s BROADWAY,LUDGATE

,LONDON ,

E C.

Adhes i ve sAgr icu l tur a l C hemis t ryAir , Indus tr ia l Use ofAlcoho l , Indus tr ia lAlum and its S u l pha tesAmmon iaAn i l ine Co lour sAn ima l Fa tsAnt i-co r r os ive Pa intsA r ch i tec tu r e , Te rms in 22

A r ch i tec tur a l Po tte r y 12

A r t ific ia l Per fumes

Ba lsamsB leach ingAgents , etc .

Bone P r oduc tsBookb ind ingB r ick-mak ingBur n ish ing B rassCa r pe t Ya rn Pr int ingCase inCe l lu lo idCement

Ce ram ic BooksC har coa lC hemica l 8

C hemica l E s says 8

C hemica l Rea ents 8C hemica lW o r s 8

C lays 12Coa l Dus t F i r ing 18

C oa l Gas By-Pr oduc ts 9

Co l l ie r y Recove r y 18

Co lour Ma tch ingy (Text i le) 16C o lou r Rec ipes 3Co lou r Theo r y 16C omb ing Mach ines 17C ompound ingO i ls , e tc 6C ondens ingAppar atus 18

C osme t ics 7

Co t ton Dye ing 16

C o t ton S p inn ing 17

Co tton Was te 17

Damask Weaving 15

Dampnes s in Bui ld ings 22Deco r ato r s ’ Books 4

Deco r a t ive Text i les 15Denta l Me ta l lurgy 18

Dis infect ion 9

D r ie r s 5

D rugs 23

Dr yingO i ls 5

Dry ingw i th Air , e tc. 10

Dye ingMa r b le , e tc . 23

Dye ing Fabr ics 16

Dyer s ’ Mate r ia ls 16Dye-s tufl

'

s 16E d i b le Fats and O i ls 7E lect r ic Lamp Deve lop

ment 21E lect r ic W i r ing 21E lec tr ic i ty in Co l l ier ies 18

Eme ry 24

E name l l ingMo n

e ta l 13

E name ls 13E nginee r ing Handbooks 19, 20

PU BLI SHED BY

SCOTT , GREENWOOD8 BROADWAV LU DGATE. LON DON

INDEX TO SUB JECTS .

PAGE

E ngraving 24

E ssent ia l O i ls 7

E vaporat ingAppa r a tus 18

E xte rna l P lumb ing 21

Fa ts 6, 7

Fau l ts in Woo l len Goods 15F lax S p inn ing 17

Food and D r ugs 23

Fr u it Pr eser ving 23

Gas F i r ing 18

G lass -mak ing Rec ipes 13

G las s Pa int ing 13

Glue-mak ingand 8

G lyce r ine 7

G r ease s 6

Gutta Per cha 11

H a t Manufac tur ing 15

Hemp S p inn ing 17

H isto r y of S taffs Po tte r ies 12Hops 22

H o t-wa te r S upp l y 21

India 11

Ind ia-r ubbe r S ubs t i tu tes 5

Inks 3 , 4 , 5 , 10

Insec t ic ides,e tc . 22

I r on-co r r os ionI r on, S c ience o f 18

Japanning 21

Jute S p inn ing 17

Lace -Mak ing 14

Lacq ue r ing 21

Lake P igments

Le ad 10

Le athe r-wo r k ingMate r’

ls 6 11

Lino leum 5

Li thogr aph ic Inks 5 23

Li thogr aphy 23

Lub r icantsManu r es 8 , 9

Meat Pr ese r vmg 23

M ed icated Soaps 7

Me ta l Po l ish ing Soaps 7

M ine r a l P igments 3

M ine ral Waxe s 6

M ine Vent i lat ion 18

M in ing, E lec t r ic ity 18N eed lewo r k 14

O il and Co lou r Rec ipes 3

O il Bo i l ing 5

O il Me r chants ’ Manua l 6

O i ls 5 , 6, 7

O zone , Indus tr ia l Use 10

Pa int Manufactur e 3

Pa int Mate r ials 3

Pa int -mate r ia l Tes t ing 4

Pa int M i x ing 3 4

Pape r -M i l l C hemis tr y 13

Pe tro leum 6

P igments 3 9

P lumbe r s ’ Books 21

Po t te r y C lays 12

Po tte r y Deco r a t ing 11

Po t te r y Manufactur e 11 12Po tte r y Mar ks 12

Powe r - loomWeavingP r ese rved FoodsP r inte r s ’ Ready Reckone rPr int ing Inks 3 ,Rec ipes 3

Re s insRing S p inn ing Fr ame

Risks o f O ccupat ionsRi ve t ing C h ina , e tc.

S chee le ’

s E s saysS ea l ingWaxesS ha le O i ls and Ta r sS hee t Me ta l Wo r k ingS hoe Po l is he sS i lk Dye ingS i lk Th r ow ing, e tc

Smoke P r event ionS oap Powde r sS p inn ingS p i r i t Va rn i she sS ta in ingMa r b le , and B onS ta in-r emovmgSoapsS tand a r d C lo thsS team D r y ingS tee l Ha r de n ingS ugar Techno logySwe e tmea ts

Ta l lowTechn ica l S choo l s , Lis tTe r r a-co tta

Te s t ing Pa int Mate r ia lsText i le Co lou r M i x ingTex t i le Des ignText i le Fab r ics 13 , 14

Text i le F i br e sTe xt i le Ma te r ia l sT imbe rTo i le t S oapmak ingVa r n is hesVege tab le Fa ts and O i lsVege tab le Pr ese r vingWa r p S iz ingWas te U t i l i s at ionWa te r , Indus t r ia l Use 10

Wate r -pr oofing Fab r icsWaxe sWeavingCa lcu la t ionsWh i te Lead and Z inc W h l lW i r ing Ca lcu la t ionsWood Dis t i l la t ionWood E xt r actsWoo d Was te U t i l isat ionWood-Dye ingWoo l Dye ingWoo l len GoodsWor sted S p inn ingWo ven Fab r icsWr i t ing InksX-Ray Wo r kYa rn S iz ingYarn Numbe r ing and Tes t

ing 14

Z inc Wh i te Pa ints

FULLPARTICULARS OF CONTENTS

Of the B ook s mentioned in th is ABRIDGED CATALOGUEw il l be found in th e fol low ing Cata logues of

C URRENT TECHNICAL B OOKS.

LI ST I .

Ar t is ts ’

Co lour s—Bone Pr oducts—Butter and Margar ine Manufacture -Case inCements—C hem ica l Wor ks (Des ign ing and E r ect ion)—C hem is t r y (Agr icu l tur al , Industr ia l , Pr act ica l and Theo r et ica l)—Co lou r M i x ing—Co lour Manufactur e—Compound ingO i ls—Decor a t ing—D r ie r s—D r ying O i ls—D r ysa l te r y—Eme r y—E s sent ia l O i ls Fa ts(An ima l , Vegetable , E d i ble) Ge lat ines Glue s G r eases Gums Inks LeadLeathe r Lub r icants O i l s O il C r ush ing Pa ints Pa int Mauufactu r ing Pa intMate r ia l Tes t ing—Pe r fumes—Pe tr o leum—Pharmacy—Rec ipes (Pa int , O il and Co lour )Res ins—S ea l ing Waxe s—S hoe Po l ishes S oap Manufac tur e S o lvents S p i r i tVar n is he s—Va r n is hes—Wh ite Lead—Wo r kshop Wr ink le s .

LI ST I I .

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Des ign ing, Dye ing,Weaving, F in ish ing)

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Ar c h i tectur a l Te rms—B rasswa r e (B r onz ing, Bu r n i s h ing, Dipp ing, Lacq ue r ing)Br ickmak ing—Bu i ld ing—Cement Wo r k—C e r amic Indus t r ies—Ch ina—C oal -dust F i r ing—Co l l ie r y Books—Concr e te—Condens ingAppa r a tus—Denta l Me ta l lurgy—D ra inageD r ugs—Dye ing—E a r thenwa r e—E lec tr ica l Books—Ename l l ing—E name l s—E nginee ring Handbooks—E vapo rat ingAppar atus—F l int G lass -mak ing—Foods—Food Pr ese rving—Fr u it Pr ese r v ing—Gas E ngines—Gas F i r ing—Gear ing—G lasswa re (Pa int ing,

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Handbook fo r O il Manu factu r e r s , Refine r s and Me r chants , and

the O il and Fat Indus t r y in Gene r a l . B y GEORG E H . HURST ,F .C .S . Th ir d Revised and Enla rged E di t ion . S eventy-fourI l lus t r at ions . 384 pp . Demy 8vo . Pr ice 103 . 6d . ne t . (Pos tfr e e , 113 . home ; 113 . abr oad . )

TE CHNOLOGY OF PETROLEUM -Oil Fields of theW o r ld—The i r H is tor y , Geogr aphy and Geology—Annua l P r oduct ion and Deve lopment—Oil-we l l Dr i l l ing—Transpo r t . B yH ENRY NEUE ERGER and H ENRY NOALHAT . Tr ans lated from the

Fr ench by J . G . MC INTO SH . 5 50 pp . 153 I l lus tra t ions . 26Plate s .

S upe r Roya l 8vo . P r ice 213 . ne t . (Pos t fr e e , 213 . 9d . home ;233 . 6d . abr oad . )

M I NERAL WAXE S :Their Pr eparation and Use s . ByRUDO LF GREGOR I U S . Tr ans la ted fr om the Ge rman. C r own 8vo .

250 pp . 32 I l lus t r a t ions . Pr ice 63 . ne t . (Pos t fr ee , 63 . 4d .

home ; 63 . 6d . abr oad . )

TH E PRACTI CAL C OMPOUND I NG OF O I LS ,

TALLOW AND GREASE FOR LUBR I CA

TI ON,ETC . By An EXPE RT O I L RE F INER . Second

E dit ion . 100 pp . Demy 8vo . Pr ice 7 3 . 6d . ne t . (Po s t fr e e ,7 3 . 10d . home ; t s . abr oad . )

THE MANUFACTURE OF LUB RI CANTS,SH OE

POLI SHE S AND LEATH ER DRE SS I NGS . ByR ICHARD BRUNN ER . Tr ans lated fr om th e S ixth Ge rman Edit ionby C HAS . SALTER . 10 I l lus tr at ion s . C r own 8vo . 170pp . Pr ice7 3 . 6d . ne t . (Pos t fr e e , 7 3 . 10d . home ; 83 . abr oad . )

TH E O I L MERCHANTS ’ MANUAL AND O I L

TRADE READY RE CKONER . Compiled byFRANK F . S HERR I FF . S econd Edit ion Revised and E n larged.

Demy Svo . 214 pp . W ith Two S h ee ts o f Tables . Pr ice 7 3 . 6d .

ne t . (Pos t fr ee , 7 3 . 10d . h ome 8s . 3d . a br oad .)

AN IMAL FATS AND O I LS : Their Pr actical Pr oduct ion . Pur ifica t ion and U se s for a gr ea t Va r ie ty of Pur poses .

The i r P r ope r t ie s,Fa ls ificat ion and Exam ina t ion . Tr ans la ted

from the Ge rman of LOU I S E DGAR ANDES . S ixty-two I llus t r at ions .

240 pp . S econd Edit ion , Revised and En la rged . Demy 8vo .

P r ice 103 . 6d . ne t . (Po s t fr e e , 103 . 10d . home ; 113 . 3d . abroad .)

VE GETAB LE FATS AND O I LS : Tli eir PracticalPr epar a t ion , Pur ifica tion

‘

and Employme nt fo r Va r ious Pur pose s ,the ir Pr ope r t ie s , Adu l te r a t ion and Exam ina t ion . Tr ans la tedfr om the Ge rman o f LOU IS E DGAR ANDES . N ine ty-four I l lust r ation s . 340 pp . S econd E dit ion . Demy 8vo . Pr ice 103 . 6d .

ne t . (Post fr ee , 113 . home ; 113 . 6d . abr oad . )

For contents of these books , see List I .


(Glue , Bone Product s and Manures . )GLUE AND GLUE TE STI NG . By SAMUE L RIDEAL

,

D .Sc . Second Edit ion , Revi sed and En larged . Demy8vo . 196 pp . 14 I l lus t ra t ions . Pr ice 103 . 6d . ne t . (Pos t fr ee ,103 . 10d . home ; 113 . abr oad . ) [170/s t publ ished .

B ONE PRODUCTS AND MANURE S An Accountof the mos t r e cen t Impr ovement s in th e Manu factu r e of Fat ,G lue , An ima l Cha r coa l , S iz e , Ge lat ine and Manur e s . B y THOMASLAM BERT , Techn ica l and Con sult ing Chem ist . Second Revi sedEdit ion . Demy 8vo . 172 page s . 17 I l lustr at ions . Pr ice 7 3 . 6d .

ne t . (Pos t fr ee , 7 3 . 10d . home ; 8 3 . abr oad . )

(See a lso Chemica l Manur es , p.

(Ch emica l s , W a ste Product s , etc . )RE I SSUE OF CHEM I CAL E SSAYS OF C . W .

SCH EELE . Fir st Published in English in 1786.

Tr ans lated fr om the Academy of Sc ience s at S tockholm , w i thAddit ions . 300 pp . Demy 8vo. Pr ice 5 3 . net . (Pos t fr ee ,

5 3 . 6d .

home ; 5 3 . 9d . abr oad . )THE MANUFACTURE OF ALUM AND TH E SUL

PHATE S AND OTH ER SALTSI

OF ALUM I NAAND I RON . Their Uses and Applications as Mordantsin Dye ing and Ca l ico Pr int ing, and the i r othe r Applicat ions inth e Ar ts , Manu factu r e s , San ita ry E nginee r ing, Agr icu ltur e and

Hor t icu ltu r e . Tr an s lated from the Fr ench of LUC I EN GE SCHWIND . 195 I l lust r a t ions . 400 pp . Roya l 8vo . Pr ice 123 . 6d .

net . (Pos t fr ee , 133 . home ; 133 . 6d . ab road .)AMM ON I A AND I TS COMPOUNDS : Their Manu

factu r e and U se s . B y CAM ILLE VI NC ENT , P r ofe s sor at the

Cent r a l S choo l of Ar ts and Manu factu r e s , Pa r is . Tr ans latedfr om th e Fr ench by M . J . SALTER . Roya l 8vo . 114 pp. Th i r tytwo I l lus t r at ions . P r ice 5 3 . ne t . (Po s t fr ee , 5 3 . 4d . home

5 3 . 6d . abroad . )CHEM I CAL WORKS : Their Design , E r ection , and

Equ ipment . B y S . S . DYSO N and S . S . C LARKSON . Roya l 8vo .

220 pp . W ith 9 Fo lding P lates and £0 I l lust r at ion s . Pr ice 213 .

ne t . (Pos t fr e e , 213 . 6d . home ; 223 . abr oad .)MANUAL OF CH EM I CAL ANALYS I S , as applied to

the As say of Fue ls , O r e s , Me ta ls , Al loy s , S alt s and othe r Mine r a lPr oduct s . B y E . PRO ST , D.Sc . Tr ans lated by J . CRU ICKSHANKSM ITH , B .Sc . Roya l 8vo . 300 page s . 44 I l lust r at ions . Pr ice123 . 6d . ne t . (Pos t fr ee , 13 3 . home ; 133 . 6d . abroad .)

TE ST I NG OF CH EM I CAL REAGENTS FOR

PUR I TY . Tr anslated from the German of Dr . C .

KRAUCH . Roya l 8vo . 350 pages . Pr ice 123 . 6d . ne t . (Post fr ee ,133 . home ; 133 . 6d . abr oad . )

For conten ts of these books , see List I .

SHALE O I LS AND TARS and the ir Pr oducts . ByDr . W . SCH E I THAUER . Tr ans lated fr om the Ge rman . Demy 8vo .

190 pages . 70 I l lust ra t ions and 4 D iagr ams . Pr ice 8 3 . 6d . net .

(Pos t fr ee ,83 . l 0d . home ; 93 . abr oad) .

TH E BY -PRODUCTS OF COAL-GAS MANUFACTURE . B y K. R. LANC E . Trans lated from the Ge rman .

C r own 8vo . 164 page s . 13 I l lus t r at ions . Pr ice 5 3 . ne t . (Pos tfr ee , 53 . 4d . home ; 53 . 6d . abr oad . ) [yust publ ished .

I NDUSTRI AL ALCOH OL . A Pr actical Manual on the

Pr oduct ion and Use of Alcoho l for Indus t r ia l Pu r po s e s and fo r

U se as a Heat ing Agen t , a s an I l luminant and a s a Sou r ce o f

Mot ive Power . B y J . G . MC INTO S H , Lectur e r on Manufactu r eand Appl icat ion s of Indus t r ia l Alcoho l a t Th e Po lyt e chn ic ,

Regent S tr ee t , London . Demy 8vo . 1907 . 250 pp . W ith 7 5

I l lus t r at ions and 25 Tables . Pr ice 7 3 . 6d . ne t . (Po st fr e e , 7 3 . l 0d .

home ; 8 3 . 3d . abr oad .)

THE UTI LI SATI ON OF WASTE PRODUCTS . ATr eat ise on the Rat iona l Ut il i sat ion , Recove r y and Tr e atment of

Waste Pr oducts of a l l k inds . B y Dr . TH EODOR RO LLER . Tr anslated fr om the Second Revised Ge rman E dit ion . S e cond Engl i shRevised E dit ion . Demy 8vo . 336 pp . 22 I l lus t r a t ion s . Pr ice7 3 . 6d . net . (Post fr ee , 83 . home ; 83 . 6d . abr oad . )

[ff‘ iis t pu blished .

ANALYS I S OF RE S I NS AND B ALSAM S . Tr ans

lated fr om the German of Dr . KARL D I ETER IC H . Demy 8vo . 340

pp . P r ice 7 3 . 6d . net . (Pos t fr ee ,7 3 . 10d . home ; 8 3 . 3d . abr oad . )

DI STI LLATI ON OF RE S I NS,RE S I NATE LAKE S

AND PI GMENTS,CARB ON PI GMENTS AND

PI GMENTS FOR TYPEWRI T I NG MACH I NE SMAN I FOLDERS

,ETC . B y VICTO R SCHWE I Z E R .

Demy 8vo. 185 pages . 68 I l lus t r at ion s . Pr ice 7 3 . 6d . ne t . (Pos tfr ee , 8 3 . home ; 83 . 3d . abr oad .)

DI S I NFE CTI ON AND D I S I NFE CTANTS . By M .

CHR I ST IAN . Tr ans lated fr om the German . Cr ow n 8vo . 112

pages . 18 I llus tr at ions . Pr ice 5 3 . ne t . (Pos t fr ee , 5 3 . 3d . home

53 . 6d . abr oad. )

(Agricu ltura l Ch emist ry and Manures . )MANUAL OF AGRI CULTURAL CHEM I STRY . B yH ERBERT ING LE , Late Lectu r e r on Agr icu l tu r a l Chemis try ,

th e Leeds Un ive r s ity ; Lectur e r in th e V ictor ia Un ive r s ity .

Th ird and Revised E dit ion . 400 pp . 16 I l lus t r at ions . Demy8vo . Pr ice 7 3 . 6d . ne t . (Pos t fr e e , 8 3 . home ; 8 3 . 6d . abr oad . )

CHEM I CAL MANURE S . Trans lated from the Fr ench

of J . FR ITSCH . Demy 8vo . I l lust r ated . 340 pp . Pr ice 103 . 6d .

ne t . (Post free , 113 . home ; 113 . 6d . abr oad . )

(See a lso B one Pr oducts and Manu r es, 15.

(Writ ing Inks and Sea l ing W axes . )I NK MANUFACTURE : I ncluding W r iting, Copying,

Lithogr aph ic , Ma r k ing, S tamping and Laundry I nks . B yS IGMUND LEHN ER . Tr a ns la ted fr om the Ge rman of the F i fthE dit ion . S econd Revised and E nla rged E ngl ish E di t ion .

C r own 8v0 . 180 page s . Th r ee I llus t r a t ion s . Pr ice 5 3 . ne t . (Pos tfr e e , 5 3 . 3d . home 5 3 . 6d . ab r oad . )

SEALI NG WAXE S ,WAFERS AND OTHER

ADH E S I VE S FOR THE H OUSEH OLD,OFFI CE

,

WORKSH O P AND FACTORY . B y H . C . STANDAGE .

C rown 8vo . 96 pp . P r ice 5 3 . ne t . (Pos t fr ee ,5 3 . 3d . home ;

5 3 . 4d . ab r oad . )

(Lead Ore s and Lead Compound s . )LEAD AND I TS C OMPOUNDS . B y THO S . LAMBE RT,Techn ica l and Cons u lt ing Chemis t . Demy 8vo . 226 pp . Fo r tyI l lus t r a t ions . Pr ice 7 3 . 6d . ne t . (Pos t fr ee ,

7 3 . 10d . home ;8 3 . 3d . abr oad . )

NOTE S ON LEAD ORE S : The ir Dist r ibution and Pro

pe r tie s . B y JAS . PA IR I E ,F .C .S . C r own 8vo . 64 page s . P r ice

13 . n e t . (Pps t fr e e , 13 . 3d . h ome 13 . 4d . abr oad . )

(White L ead and Z inc White Paints , see

( Indus t ria l Hygiene . )TH E RI SKS AND DANGERS TO H EALTH OF

VARI OUS O C CUPATI ONS AND TH E I R PRE

VENTI ON . By LEO NARD A. PARRY,M.D.

,B .Sc .

196 pp . Demy 8vo . P r ice 7 3 . 6d . ne t . (Post fr ee ,

7 3 . 10d . home ; 8 3 . ab road .)

( Indus t ria l Us es of Air , Steam and

Water . )DRYI NG B Y MEANS O F A I R AND STEAM . Explana t ion s , Formu lae ,

and Tables fo r Use in Pr ac t ice . Tr ansla ted fr om the Ge rman o f E . HAUS BRAND . S econd RevisedEngl ish Edit ion . Two fo lding D iagrams , Th ir teen Table s , and

Two I l lus t r a t ion s . C r own 8vo . 7 6 pp . Pr ice 53 . ne t . (Po‘

st

fr ee,5 3 . 3d . home ; 5 3 . 6d . abr oad .)

(See a l so E vapor a ting,Condensing and Cooling Appa ra tus ,

”

p.

PURE AI R,O Z ONE AND WATER . A Practical

Tr ea t ise o f t he i r U t i l isa t ion and Va lue in O il , Gr ease , Soap , Pa int ,G lue and othe r Indus t r ie s . B y W . B . COWE LL . Twe lve I l lust r a t ion s . C r own 8vo . 8 5 pp . Pr ice 5 3 . ne t . (Pos t fr ee ,

5 3 . 3d .

home ; 5 3 . 6d . abr oad . )

For contents of thesr booles , see List I I I .


A TREATI SE ON CERAM I C I NDUSTRI E S . AComple te Manua l fo r Potte r y , Ti le ,

and B r ick Manufactu r e r s . B yE M I LE B OURRY. A Revis ed Tr ans lat ion fr om the Fr ench

,w ith

some C r it ica l No te s by ALFRED B . S EARLE . Demy 8vo . 308

I l l us t r a t ions . 460 pp. Pr ice 123 . 6d . ne t . (Pos t fr ee ,133 . home ;

13 3 . 6d . ab road . )

ARCH I TE CTURAL POTTERY . B r icks,Tiles , Pipe s ,

E name l led Te r r a-cot tas , O r dina ry and Inc r u s ted Q ua r r ie s , S tonew a r e Mosa ics

,Fai

'

ence s and Ar ch itectu ra l S tonewa r e . B y LEONLEFEVRE . Tr ans lated fr om the Fr ench by K. H . B IRD

,M.A. ,

and W . MOO RE B INN S . W ith F ive Plate s . 950 I l lust r at ions inthe Text , and nume r ous e st ima tes . 500 pp . Roya l 8vo . P r ice15 3 . nc t . (Pos t fr ee , 15 3 . 6d . home ; 163 . 6d . abr oad .)

THE ART OF RI VETI NG GLASS ,CH I NA AND

EARTH ENWARE . B y J . HOWORTH . Second

Edit ion . Pape r Cover . P r ice 13 . ne t . (B y pos t , home or abr oad ,13 . 1d . )

NO TE S O N POTTERY CLAYS . The Dis tr ibution ,

P r ope r t ie s , Us e s and Ana lyse s of B a l l C lays , Ch ina C lays and

C h ina S tone . B y JAS . FA I R I E , F .C .S . 132 pp . C r own 8vo .

Pr ice 3 3 . 6d . ne t . (Po st fr ee ,33 . 9d . home ; 3 3 . 10d . abr oad . )

H OW TO ANALYSE CLAY . By H . M . ASH B Y. Demy8VO . 72 pp . 20 I l lu s t r a t ions . Pr ice 33 . 6d . ne t . (Pos t fr e e ,

3 3 . 9d . home ; 3 3 . 10d . ab r oad . )

A R e is su e of

TH E H I STORY OF TH E STAFFORDSH I RE POT

TERI E S ; AND TH E RI SE AND PRO GRESS

OF TH E MANUFACTURE OF POTTERY AND

PORCELAI N . W ith Re fe r ence s to Genuine Specimens ,

and No t ices o f Em inent Potte r s . B y S IMEO N S HAW. (O r igina l lypubli shed in 265 pp. Demy 8vo . Pr ice 5 3 . ne t . (Pos tfr ee

,5 3 . 4d . home ; 5 3 . 9d . abr oad . )

A R e is su e of'

TH E CH EM I STRY OF TH E SEVERAL NATURALAN D ART I F I C I AL H ETERO GENEOUS COMPOUNDS U SED I N MANUFACTURI NG POR

GELAI N , GLASS AND POTTERY . By S IMEONS HAW . (O r iginal ly publ ished in 7 50 pp . Roya l 8vo .

Pr ice 103 . ne t . (Pos t fr ee ,103 . 6d . home ; 123 . abr oad .)

B RI TI SH POTTERY MARKS . B y G . W OOLLI SCROFT

RH EAD. Demy 8vo . 3 10 pp . W ith ove r Twe lve -hundr ed I l lust r at ions of Ma r ks . Pr ice 7 3 . 6d . ne t . (Pos t fr ee , 83 . home ;8 3 . 3d . abroad . )

For contents of these books , see List I I I .

(Gla s swa re , Gla s s Sta ining and Pa int ing. )REC I PE S FOR FLI NT GLASS MAKI NG . By a

B r it ish Glas s Ma s te r and Mixe r . S ixty Rec ipes . B e ing Leave sfr om the MixingB ook of seve r a l expe r ts in the Fl int G las s Tr ade ,conta in ing up

-to-date r ec ipe s and va luable informat ion a s to

C rysta l , Demi -crysta l and Co lou r ed G las s in it s many va r ie t ie s .

I t conta ins th e r e c ipe s for cheap me ta l su i ted to pr e s s ing, blowing, e tc .

, as we l l as the mo s t cos t ly c r ys ta l and r uby . S econdEdit ion . C r own 8vo . Pr ice 103 . 6d . ne t . (Pos t fr ee , 103 . 9d .

home ; 103 . 10d . abr oad .)

A TREATI SE ON TH E ART OF GLASS PA I NTI N G . Pr efaced with a Review of Ancient Glas s . ByE RN EST R. SHEEL ING . W ith One Co lou r ed P la te and Th i r tyseven I l lust rat ions . Demy 8vo . 140 pp . Pr ice 7 3 . 6d . ne t .

(Pos t fr ee , 7 3 . 10d . home ; 8 3 . ab r oad .)

(Paper Making and Te s t ing. )THE PAPER M I LL CH EM I ST . By HENRY P . STEVEN S ,

M .A. ,Ph .D . , F . I .C . Roya l I 2mo . 60 I l lus t r at ion s . 300 pp .

Pr ice 7 3 . 6d . ne t . (Po s t fr e e , 7 3 . 9d . home ; 7 3 . 10d . ab r oad . )

THE TREATMENT OF PAPER FOR SPE C I AL

PURPO SE S . By L . E . ANDES . Translated from the

Ge rman . C r own 8v‘

o . 48 I l lus tr at ion s . 250 pp . P r ice 63 . ne t .

(Po s t fr ee , 63 . 4d . home ; 63 . 6d . abr oad . )

(Ename l l ing on Meta l . )ENAMELS AND ENAMELLI NG . For Ename l

Make r s , Wo r ke r s in Go ld and S i lve r , and Manufactu r e r s o f

Obj ect s of Ar t . B y PAU L RAN DAU . S econd and RevisedEdit ion . Tr ans lated fr om the Ge rman . W ith 16 I llus tr at ion s .

Demy 8vo . 200 pp . Pr ice 103 . 6d . ne t . (Pos t fr ee ,103 . 10d .

home ; 113 . abr oad . )THE ART OF ENAMELLI NG ON METAL . By

W . NORMAN BROWN . S econd Edit ion , Revised . C r own 8vo .

60 pp . Pr ice 33 . 6d . ne t . (Pos t fr ee , 33 . 9d . home ; 33 . 10d .

abr oad . )

(Text ile and Dye ing Subj ect s . )THE FI N I SH I NG OF TEXT I LE FABRI C S (Woollen ,

Wo r s ted , Un ion,and othe r C loth s ) . B y RO BERTS B EAUMO NT .

W ith 150 I l lus tr at ions o f Fibr es, Yar n s and Fabr ics , a lso S ec t ional

and othe r D r awings o f F in ish ingMach ine r y . Demy 8vo . 260 pp .

Pr ice 103 . 6d . ne t . (Pos t fr e e , 103 . 10d . home ; 113 . 3d . abr oad .)STANDARD CLOTH S . By RO BE RTS B EAUMONT.

[I n the Pr ess .

FI BRE S USED I N TEXTI LE AND ALLI ED I N

DU STRI E S . By C . AIN SWO RTH MITCHE LL , B .A.

and R. M . PR I DEAUx ,F I .C . W ith 66 I l lus t r a

t ions special ly d r awn dir ect fr om the Fi br e s . Demy 8vo .

200 pp . Pr ice 7 3 . 6d . ne t . (Pos t fr ee , 7 3 . 10d . home 8 3 . ab road .)

DRE SS I NGS AND F I N I SH I NGS FOR TEXT I LE

FABRI C S AND THE I R APPLI CAT I ON . Descr i pt ion of a l l the Mate r ia ls u sed in D r e s s ing Text i le s :Th e i rSpec ia l Pr ope r t ies , the pr epa r a t ion of D r e ss ings and th e i r employment in F in ish ing Linen , Cotton , W ool len and S ilk Fab r ics .

Fi r epr oo f and Wa te r pr oo f D r e s s ings , toge the r w ith the p r inc ipa lmach ine r y emp loyed . Tr ans lated fr om the Th i rd Ge rman

Edit ion of FR IEDR IC H POLLEYN . Demy 8vo . 280 pp . S ixtyI l lust r at ions . P r ice 7 3 . 6d . net . (Pos t fr ee , 7 3 . 10d . home ;83 . abr oad .)

THE CHEM I CAL TE CHNOLO GY OF TEXT I LE

FI BRE S : Their O r igin ,Str uctur e , Pr eparation , Wash

ing, B leach ing, Dye ing, Pr int ing and D r e s s ing. B y Dr . GEORGVON GEORG I EVI C S . Tr ans lated fr om th e Ge rman by CHARLESSALTER . 320 pp . For ty

-seven I l lust r at ions . Roya l 8vo . P r ice103 . 6d . net . (Pos t fr ee ,

113 . home ; 113 . 3d . abr oad . )

POWER-LOOM WEAVI NG AND YARN NUMB ERI N G

,According to Var ious Systems

,with Conve r s ion

Table s . Tr ans lated fr om the Ge rman ofANTHON GRUN ER .,With

Twenty-s ix Diagrams in Colours . 150 pp . C r own 8vo . Pr ice7 3 . 6d . ne t . (Post fr e e , 7 3 . 9d . home ; 83 . abr oad . )

TEXTI LE RAW MATERI ALS AND TH E I R CON

VERS I ON I NTO YARNS . (The Study of the RawMa ter ia ls and the Techno logy of th e Spinn ing P r oce ss . ) B yJU L I US Z I PS ER . Tr ans lated from Ge rman by C HARLES SALTER .

302 I l lust r a t ions . 500 pp . Demy 8vo . P r ice 103 . 6d ne t .

(Post fr ee , 113 . home ; 113 . 6d . ab r oad . )

GRAMMAR OF TEXTI LE DE S I GN . B y H . N ISBET ,

Weaving and De s ign ing Mas te r , B o l ton Mun ic ipa l Techn ica lS chool . Demy 8vo . 280 pp. 490 I l lus t rat ions and D iagr ams .

P r ice 63 . ne t . (Post fr ee ,63 . 4d . home ; 63 . 6d . abr oad . )

ART NEEDLEWORK AND DE S I GN . PO I NTLACE . AManual ofApplied Ar t for Secondary Schoolsand Cont inua t ion C las se s . B y M. E . W I LK IN SON .

" Oblongquar to. W ith 22 P lates . Bound in Ar t Linen . Pr ice 33 . 6d .

net . (Post fr e e , 3 3 . 10d . home ; 43 . abr oad . )

H OME LACE -MAK I NG . A Handbook fo r Teache r s and

Pup i ls . B y M. E . W . M I LROY. C r own 8vo . 64 pp . W i th 3

Plates and 9 D iagr ams . P r ice 13 . ne t . (Pos t fr e e ,13 . 3d . home ;

13 . 4d . abroad .)

For contents of these books , see List I I .


(Dye ing, Colour Print ing, Match ingand Dye =s tuffs . )

TH E COLOUR PRI NTI NG OF CARPET YARNS .

Manua l for Co lour Chem is ts and Text i le Pr inte r s . B y DAVIDPATERSON , F .C .S . S even teen I l lus t r a t ions . 136 pp . Demy8VO . Pr ice 7 3 . 6d . ne t . (Pos t fr e e , 7 3 . 10d . home ; 8 3 . abr oad . )

TEXTI LE C OLOUR M I X I NG . By DAVID PATERSON .

Forme r ly publ i sh ed unde r t it le of “ Sc ience o f Co lour M ixingS econd Revised Ed it ion . Demy 8 vo . 140 pp . 41 I l lust ra t ions ,w ith 5 Co lour ed Plate s and 4 Plates show ing Dyed Spec imens .

P r ice 7 3 . 6d . ne t ., (Post fr ee , 7 3 . 10d . h ome ; 83 . abr oad . )

[f as t published .

DYERS ’

MATERI ALS An Int roduct ion to the Examinai w tion , Eva lua t ion and Appl icat ion o f the mos t impor tant Sub" T '

s tances use d in Dye ing, Pr int ing, B leach ing and Fin ish ing. B

PAUL H E ERMAN , Ph .D . Tr ans lated fr om th e Ge rman by A .

W R IGHT , M.A. B .s e . Twenty-four I l lu s t r at ions .

Lift. Cr own 8vo . 150 pp . Pr ice 5 3 . ne t . (Pos t fr ee ,5 3 . 4d . home

5 3 . 6d . abr oad .)COLOUR MATCH I NG ON TEXTI LE S . A Manualintended for the use of S tudents of Co lour Chemistr y , Dye ingand

Text i le Pr int ing. B y DAVID PATERSO N , F .C .S . Colour ed Fr ont isp iece . Twenty

-n ine I l lust r at ions and Fourteen Specimens of

Dyed Fab r ics. Demy 8vo . 132 pp . Pr ice 7 3 . 6d . ne t . (Pos tfr ee , 7 3 . 10d . home ; 8 3 . abr oad .)

COLOUR : A HANDB OOK OF THE THEORY OF

COLOUR. By GEO RGE H . HURST,F .C .S . With Ten

Colour ed Plates and S eventy-two I l lus tr at ions . 160 pp . Demy8V0 . Pr ice 7 3 . 6d . ne t . (Pos t fr e e , 7 3 . 10d . home 83 . abr oad .)

R eis su e of

THE ART OF DYE I NG WOOL , S I LK AND

COTTON . Tr anslated from the Fr ench of M. HELLOT,

M. MACQUE R and M . LE P ILEUR D ’APLI GNY . Fir st Publ ished in

Engl ish in 1789 . S ix Plate s . Demy 8vo . 446 pp . Pr ice 5 3 . net .

(Post fr ee , 5 3 . 6d , home ; 63 . abr oad . )T HE CHEM I STRY OF DYE -STUFFS . By Dr . GEORGVON GEORG I EVI C S . Tr ans lated fr om the Second German E dit ion .

412 pp. Demy 8vo . P r ice 103 . 6d . ne t . (Post fr ee , 113 . home ;113 . 6d . abroad .)

THE DYE I NG OF“

COTTON FABRI C S : A PracticalHandbook for the Dye r and S tudent . B y FRANKL IN B EEC H ,Pr actica l Co lour is t and Chem is t . 272 pp . Fo r ty

-four I l lust r ations of B leach ing and Dye ingMach ine ry . Demy 8vo . Pr ice7 3 . 6d . net . (Pos t fr ee , 7 3 . 10d . h ome ; 8 3 . ab r oad . )

THE DYE I NG OF WO OLLEN FABR I CS . ByFRANKL IN B EECH , Pr act ica l Co lour is t and Chem is t . Th i r tyth r e e I l lus tr at ions . Demy 8VO . 228 pp . Pr ice 7 3 . 6d . ne t .

(Pos t fr ee , 7 3 . 10d . home ; 83 . ab road .)

For contents of these books, see List I I .

(S il k Manufact ure . )S I LK THROW I NG AND WASTE S I LK SPI NNI NG . By HoLLI N s RAYNER . Demy 8vo . 170 pp.

117 I l lus . Pr ice 5 s . ne t . (Pos t fr ee , Ss . 4d . home ; Ss . 6d . abr oad .)

(B leach ing and Bleach ing Agent s . )A PRACTI CAL TREATI SE ON THE B LEACH I NG

OF LI NEN AND COTTON YARN AND FAB RI C S .

B y L. TA I LFER , Chem ica l and Mechan ica l E nginee r . Tr anslated fr om the Fr ench by JOHN GEDDES MC INTO S H. Demy 8vo .

303 pp . Twenty I l lus . Pr ice 12 3 . 6d ,. ne t . (Pos t fr ee , 13 5 .

home ; 133 . 6d . abr oad . )M ODERN B LEACH I NG AGENTS AND DETER

GENTS . By Pro fessor MAX B OTTLE R . Translatedfr om the Ge rman . C r own 8vo . 16 I l lu s t r a t ion s . 160 page s .

Pr ice 5 3 . ne t . (Pos t fr ee ,5 s . 3d . h ome ; 5 3 . 6d . ab r oad .)

(Cotton Spinning, Cotton W a s te and

Cotton Comb ing. )COTTON SPI NNI NG (Fir st Year ) . By THOMASTHORN LEY , Spinn ing Mas te r , Bo lton Techn ica l Schoo l . 160 pp .

84 I l lus t rat ions . C r own 8vo . S econd Impr e s s ion . Pr ice 33 .

ne t . (Pos t fr ee ,3 5 . 4d . home ; 33 . 6d . ab r oad . )

COTTON SPI NN I NG ( Inte rmediate , or Second Year ) .B y T. THORN LEY. 2nd . Impr e s s ion . 180pp . 70 I l lus . C rown 8vo.

Pr ice 5 s . ne t . (Pos t fr e e ,5 8 . 4d . home ; 5 5 . 6d . abroad .)

COTTON SPI NN I NG (Honour s , or Third Year ) . ByT . THORN LEY . 216 pp 74 I l l ust r a t ions . C r own 8vo . SecondEdit ion . P r ice Ss . ne t . (Pos t fr e e , 5 s . 4d . home ; Ss . 6d . abr oad . )

COTTON COMB I NG MACH I NE S . By ,TI—I O S . THORN

LEY , Spinn ing Maste r , Techn ica l S choo l , Bo lton . Demy 8vo .

117 I l lus tr at ions . 300 pp . Pr ice 7 3 . 6d . ne t . (Post fr ee , 83 .

home ; 88 . 6d . ab r oad .)COTTON WASTE I ts Pr oduction , Characte r istics ,

Regu la t ion , Open ing, Ca r ding, S pinn ingandW eaving. B y THOMASTHO RNLEY . Demy 8vo . 286 page s . 60 I l lust r a t ions . P r ice 7 s . 6d .

ne t . (Po st fr e e , 7 s . l 0d . home ; 8 3 . abr oad . )TH E RI NG SPI NN I NG FRAME : GU I DE FOR

OVERLOOKERS AND STUDENTS . By N . B OOTH .

C r own 8vo . 76 pages . Pr ice 3 3 . ne t . (Pos t fr ee ,35 . 3d . home ;

3 5 . 6d . abr oad .)

(Flax, Hemp and Jute Spinning. )MODERN FLAX , H EMP AND JUTE SPI NN I NG

AND TW I STI NG . A Pr actical Handbook for the use

of F lax , Hemp and Jute Spinne r s , Th r ead , Tw ine and RopeMake r s . B y H ERBERT R. CARTER , Mil l Manage r , Text i le Exper tand Enginee r , Exam ine r in Flax Spinn ing to t he C i ty and Guildsof London Ins t i tute . Demy 8vo . 1907 . W ith 92 I l lus t r at ions .

200 pp . Pr ice 7 3 . 6d . ne t . (Post fr ee , 7 3 . 9d . home ; 8 5 . abr oad . )

RE COVERY WORK AFTER PI T F I RE S . By ROBERTLAMPRECHT , M in ing Enginee r and Manage r . Tr ans lated fr omthe Ge rman . I l lus t r a ted by S ix la rge Pla te s , conta in ing Seventys ix I l lus tr at ions . 175 pp . Demy 8vo . Pr ice 103 . 6d . net . (Pos tfr ee . 103 . 10d . home ; l l s . a b r oad . )

VENTI LAT I ON I N M I NE S . B y RO BE RT WAB NER ,

M in ing E nginee r . Tr ans lated fr om the Ge rman . Roya l 8vo .

Th i r ty P late s and Twen ty-two I l lus t r at ion s . 240 pp . Pr ice

108 . 6d . ne t . (Pos t fr e e ,l l s . home ; l l s . 3d . ab r oad . )

TH E ELE CTR I CAL E Q U I PMENT OF COLLI ERI E S .

B y W . GALLOWAY DUNCAN and DAVID PENMAN . Demy 8vo .

3 10 pp . 155 I l lus t r a t ions a nd D iagr ams . Pr ice 103 . 6d . ne t .

(Pos t fr ee , 1l s . home ; l 1s . 3d . abr oad .)

(Denta l Meta l lurgy . )DENTAL METALLURGY : MANUAL FOR STU

DENTS AND DENTI STS . By A. B . GR IFF ITH S ,Ph .D . Demy 8vo . Th i r ty-s ix I l lus t r a t ions . 200 pp . Pr ice7 5 . 6d . ne t . (Pos t fr ee , 7 5 . 10d . home ; 8 5 . ab r oad .)

(Enginee ring, Smoke Prevent ion and

Meta l lurgy . )THE PREVENTI ON OF SMOKE . Combined with

th e E conomica l Combus t ion of Fue l . B y W . C . PO PPLEWELL ,M .S c .

, A.M . Ins t ., C . E . , Cons u l t ing E ngine e r . For ty

-six I llust r a t ions . 190 pp . Demy 8vo . Pr ice 7 8 . 6d . net . (Pos t fr ee ,

7 5 . l 0d . home ; 8 5 . 3d . ab r oad . )GAS AND COAL DU ST FI RI NG . A C r itical Review

o f the Va r ious Appl iance s Patented in Ge rmany fo r th i s pu rposes ince 1885 . B y ALBERT PUTS C H . 130 pp . Demy 8370 . Tr anslated fr om th e Ge rman . W ith 103 I l l us t ra t ions . Pr ice 5s . ne t .

(Pos t fr e e ,Ss . 4d . home ; 5 3 . 6d . ab r oad . )

TH E H ARDEN I NG AND TEMPERI NG OF STEEL

I N THEORY AND PRACTI CE . By FR IDO L INRE I S ER . Tr ans la ted fr om the Ge rman of the Th i r d Edit ion .

C r own 8VO . 120 pp . P r ice 5 3 . ne t . (Pos t fr e e , 5 s . 3d . home ;

5 3 . 4d . abr oad . )

S I DEROLO GY : TH E SC I ENCE OF I RON (TheCons t itu t ion of I r on Al loys and S lags ) . Tr ans la ted fr omGe rman of HAN N S FRE IHERR v . JiJ

'

PTN ER . 350 pp . Demy 8vo .

E leven Pla te s and Ten I l lus t r a t ions . Pr ice 103 . 6d . ne t . (Postfr ee , l l s . h ome ; l l s . 6d . ab r oad . )

EVAPORATI NG, CONDENS I NG AND COOLI NG

APPARATUS . Explanations , Fo rmulae and Tablesfor U s e in Pr act ice . B y E . HAU S BRAND , E ngine e r . Tr ans latedby A. C . WR I GHT ,

M.A. B .S c. W ith Twen tyone I l lus t r a t ions and S eventy-s ix Table s . 400 pp. Demy 8vo .

Pr ice 105 . 6d . ne t . (Pos t fr ee ,l l s . home ; l l s . 6d . abr oad . )

For contents of these books, see Lis ts I I and I I I .


VO LUME K I L S U I E N G E 0 1" W O R K S M A N A G E

MENT . B y JO HN B ATEY. 232 page s . Pr ice 4s . net .

(Pos t fr ee ,4s . 3d . home 4s . 6d . abr oad .)

VO LUME XI I I .

-THE CALCULUS FOR ENG I NEERS .

B y EWART S . ANDREWS , B .S c .E ng. and H . BRYONHEYWOOD , D .Sc . (Pa r i s) , B .s e . 284 page s . 102 I l lus t r at ion s . W ith Table s and Wo r ked Example s . Pr ice 48 . ne t . (Pos tfr ee , 45 . 3d . home ; 43 . 6d . abr oad .)

VO LUME X IV.—LATH E S : Their Constr uction and

Ope r a t ion . B y G . W . B URLEY . 244 pages . 200 I l lus t r at ions .

Pr ice 38 . 6d . ne t . (Pos t fr ee ,3 8 . 9d . home ; 48 . ab r oad . )

[yus t publ ished .

VO LUME XV.—STEAM B O I LERS AND COMB US

TI ON . By JO HN B ATEY . 220 page s . 18 Diagr ams .

Pr ice 48 . ne t . (Post fr ee , 48 . 3d . home ; 48 . 6d . ab road . )[31m publ ished .

VO LUME_XVI .

—RE I NFORCED CONCRETE I N

PRACTI CE . B y A. ALBAN H . SCOTT . 190 page s .

130 I l lus t r a t ion s and D iagr ams and 2 Fo lding Plates . Pr ice48 . net . (Po st fr ee ,

48 . 3d . home ; 48 . 6d . abr oad .)[yus t pu bl ished .

[ I N PREPARATION"

PORTLAND CEMENT. I ts Pr ope r ties and Manu

factur e . B y P . C . H . W EST , F.C .S .

TE STI NG OF MACH I NE TO OLS . By G . W . B URLEY .

B RI DGE FOUNDATI ONS . B y W . B URNS IDE ,

CALCULATI ONS FOR A STEEL FRAME B U I LDI N G . B y W . C . CO CKING ,

M.C . I .

GEAR GUTTI NG . By G . W . B URLEY .

M OVI NG LOADS BY I NFLUENCE LI NE S AND

OTH ER M ETH ODS . B y E. H . SPRAG UE,A.M . I .C . B.

TH E STAB I LI TY OF ARCH E S . B y E . H . SPRAGUE,

DRAW I NG OFFI CE PRACTI CE . B y W . C LEGG .

E STI MATI NG STEELWORK FOR B U I LD I NGS . ByB . P . F . GLEED and S . B YLANDER .

THE THE ORY OF THE CENTRI FUGAL AND

TURB O PUMP. By J.W E LLS .

STRENGTH OF SH I PS . B y JAME S B E RTRAM THOMAS .

STAB I LI TY OF MASONRY . By E . H . SPRAGUE .

MACH I NE SH OP PRACTI CE . B y G . W . B URLEY.

For contents of these books , see List I I I .

(Sanita ry Plumb ing, Meta l Work , etc . )EXTERNAL PLUMB I NG WORK . A Tr eatise on

Lead Wo r k for Roo fs ; B y JOHN W . HART , R.P .C . 180 I l lus tr at ion s . 272 pp . Demy 8 r o . Se cond Edit ion Revis ed . Pr ice7 8 . 6d . ne t . (Pos t fr ee . 7 8 . l 0d . h ome ; 8 8 . ab r oad . )

H I NTS TO PLUMB ERS ON JO I NT W I PI NG,PI PE

B END I NG AND LEAD B URN I NG . Third Edition,Revised and Cor r ected . B y JOHN W . HART , R.P .C . 184 I l lust r a tions . 313 pp . Demy 8vo . Pr ice 7 8 . 6d . ne t . (Pos t fr ee ,

88 . home ; SS . t‘

d . abr oad . )SAN I TARY PLUMB I NG AND DRAI NAGE . ByJOH N W . HART. Demy 8vo . W ith 208 I l lus tr at ions . 250 pp .

1904 . Pr ice 7 8 . 6d . ne t . (Po s t fr e e , 7 8 . 10d . home ; 8 8 . abr oad . )TH E PRI NC I PLE S AND PRACTI CE OF D I PPI NG ,

B URN I SH I NG ,LACQ UERI NG AN D B RON Z

I N G BRASS WARE . ByW . NO RMAN B ROWN . 48 pp .

C r own 8vo . Pr ice 38 . ne t . (Pos t fr e e , 38 . 3d . home and abr oad .)A H ANDB OOK ON JAPANN I NG . For I ronwar e ,Tinwa r e , and Wood , e tc . B y W I LL IAM NORMAN BROWN .

S econd E di t ion . 70 pages . 13 I l lus t r a t ions . C rown 8vo . Pr ice38 . 6d . ne t . (Pos t fr ee , 38 . 9d . home :48 . ab road . )

TH E PRI NC I PLE S OF H OT WATER SUPPLY . B yJOHN W . HART

,R.P .C . W i th 129 I l lus t r at ions . 17 7 pp . Demy

8vo . P r ice 7 3 . 6d . ne t . (Pos t fre e , 7 8 . l od . home ; 8 3 . abr oad .)SHEET METAL WORKI NG . Cutting,

Punching,

Be nding, Fo lding, Pr e s smg,D r aw ing and Emboss ing Me ta ls

,

w i th Mach ine r y for same . B y F . GEORG I and A. S C HUBERT .

Tr ans la ted fr om the Ge rman . Demy 8vo . 160 pages . 125 D r awings and I l lus tr at ions . 2 Fo lding Plates . Pr ice 7 8 . 6d . ne t .

(Pos t fr ee , 7 8 . l od . home ; 8 8 . abr oad . ) [yus t publ ished .

(Elect ric W iring, etc . )THE DEVELOPMENT OF THE I NCANDE S CENT

ELE CTRI C LAM P. By G . B AS IL BARHAM ,Demy 8vo . 200 page s . 2 Plate s , 25 I l lus tr at ion s and 10 Tab le s .

Pr ice 5 8 . ne t . (Pos t fr ee , 5 8 . 4d . home 5 8 . 6d . ab road . )

WI RI NG CALCULATI ONS FOR ELE CTRI C

LI GH T AND POWER I NSTALLATI ONS . APr ac t ica l Handbook contain ing W i r ing Table s , Ru le s , and

Fo rmulae for the U se ofAr ch i tects,Enginee r s , M in ingEnginee r s ,

and E lec tr ic ian s , W ir ing Cont r actor s and W i r emen , e tc . B y G .

W . LUMM I S PATERSON . C r own 8VO . 96 page s . 35 Table s .

Pr ice 5 3 . net . (Post fr ee , 5 8 . 3d . home 5 8 . 6d . abr oad .)ELE CTRI C W I RI NG AND F I TTI NG . B y SYDNEY F.

WALKER , R.N . , e tc . , e tc .

C r own 8vo . 150 pp . W ith I l lus t r at ion s and Tables . Pr ice 5 8 .

ne t . (Pos t fr ee , 5 8 . 3d . home; - 53 .

(Brewing and Botanica l . )H OPS I N TH E I R B OTAN I CAL , AGRI CULTURAL

AND TE CHN I CAL ASPE CT,AND AS AN

ARTI CLE OF COMMERCE . B y EMMANUE L GROS S .

Tr ans lated fr om the Ge rman . 78 I l lus . 340 pp . Demy 8vo . Pr ice108 . 6d . ne t . (Pos t fr ee , 118 . home 118 6d . ab r oad . )

I NSE CTI C I DE S ,FUNG I C I DE S AND WEED

KI LLERS . By E . B OUROART ,D.Sc . Trans lated from

the Fr ench . Revised and Adapted to B r it ish S tandar ds and

Pr act ice . Demy 8vo . 450 page s , 83 Table s , and 12 I l lus trat ions .

Pr ice 125 . 6d . ne t . (Post fr ee , 138 home ; 138 . 6d . abr oad .)(For Agr icu l tur a l Chemis try , see 15. 9

(W ood Pr oduct s ,Timber and W ood W a s te .

WOOD PRODUCTS . D I STI LLATE S AND EX

TRACTS . B y P . DUME SNY, Chemical Engineer ,Expe r t be for e the Lyons Comme r c ia l Tr i buna l , Membe r O f the

I n te rna t iona l As soc iat ion O f Lea the r Chem is ts ; and J . NOYER .Tr ans la ted fr om the Fr ench by DONALD GRANT . Roya l 8vo .

320 pp . 103 I l lus tr a t ion s and Nume r ous Table s . Pr ice 105 . 6d .

ne t . (Post fr e e , l l s . home ; 118 . 6d . ab r oad )T I M B ER : A Compr ehens ive S tudy of Wood in al l it sAspects (Comme rc ia l and B o tan ica l) , sh ow ing th e diffe r entAppl ica t ions and Use s o f Timbe r in Va r ious Tr ade s ,

e tc . Tr an slated fr om t h e Fr ench of PAU L C HARPENTIER . Roya l 8vo . 437

178 I l lu s t rat ion s . Pr ice 128 . 6d . ne t . (Pos t fr ee , 138 .

h ome ; 148 . ab r oad . )

TH E UT I LI SATI ON OF WOOD WASTE . Tr ans

la ted fr om the Ge rman o f E RN ST HU BBARD . C r own SVO . 192 pp .

50 I l lus . Pr ice 5 8 . ne t . (Pos t fr ee , 5 s . 4d home ; 5 8 . 6d . abroad . )

(See a lso Utilisa tion of Wa ste Pr oducts , 15.

(Build ing and Arch itecture . )ORNAMENTAL CEMENT WORK . By OL IVE RW HEATLEY . Demy 8vo . 83 I l lus tr at ion s . 128 pp . Pr ice SS .

ne t . (Pos t fr ee , 5 8 . 4d . home ; 5 8 . 6d . abr oad . )TH E PREVENTI ON OF DAMPNE S S I N BU I LD

I NG S ; With Rema rk s on the Causes,Nature and

E ffe ct s of Sa l ine , EH-I or e scence s and D r y-rot , for Ar ch ite cts ,

B u i lde r s , Ove r s ee r s , P las te r e r s , Pa inte r s and Hous e Owner s .

B y ADOLF W I LHELM KE IM .

’

1 r ans lated fr om the Ge rman o f th e

s econd r evised Edit ion by M . J . SALTER , F. I .C . , F .C S . E igh tCo lour ed Pla te s and Th i r teen I l lust r a t ions . C r own 8vo . 115

Pr ice 5 8 . net . (Pos t fr ee ,3d . home , 5 8 . 4d . abr oad .)

HANDB OOK OF TE CHN I CAL TERM S USED I N

ARCH I TE CTURE AND B U I LD I NG , AND THE I R

ALLI ED TRADE S AND SUB JE CTS . By AUGUSTIN E C . PASSMORE . Demy 8vo . 380 pp . Pr ice 7 8 . 6d . ne t .

(Po s t fr ee , 8 8 . home : 8 s . 6d . ab r oad .)

For contents of these books. w e List I I I .


PR I N T E R S ’

A N D S T AT I O N E R S ’

R E A D YRE CKONER AND COMPEND I UM . Compiled byVICTO R GRAHAM . C r own 8vo . 112 pp . 1904 . Pr ice 38 . 6d . ne t .

(Pos t fr e e , 38 . 9d . home ; 3 3 . 10d . ab r oad . )ENGRAVI NG FOR . I LLUSTRATI ON . H I STORI

CAL AND PRACTI CAL NOTE S . By J . KIRKBR IDE .

7 2 pp . TW O Plate s a nd 6 I l lus t r a t ions . C r own 8VO . Pr ice28 . 6d . ne t . (Pos t fr ee , 28 . 9d . home 28 . l 0d . abr oad . )

(For P r inting I nks , see p.

(Bookb ind ing )PRACTI CAL B OOKB I ND I NG . By PAUL ADAM .

Tr ans la ted fr om t h e Ge rman . C r own 8vo . 180 pp . 127 I l lust r ations . Pr ice 5 8 . ne t . (Pos t fr e e , 5 5 . 4d . home ; SS . 6d . abr oad .

(Suga r Refining. )THE TE CHNOLOGY OF SUGAR : Pr actical Tr eatise

on the Mcde r n Me thods O f Manufactu r e O f Suga r fr om the S ugar

Cane and S uga r B ee t . B y JOHN GEDDES MC I NTO S H . Th i r d Revised and E n la rged Edi t ion . Demy 8vo . [N ew Edition in the Pr ess .

(See E vapor a ting,Condensing, etc. , Appar a tus ,

”

p.

(Eme ry . )EMERY AND TH E EMERY I NDUSTRY . Tr anslated fr om th e Ge rman o f A . HAE N I C . Cr own 8vo . 45 I l lus .

104 pp . Pr ice 5 8 . ne t . (Post fr ee , 5 3 . 3d . home ; 58 . 6d . abr oad . )

(Bib l iography . )CLAS S I FI ED GU I DE TO TE CHN I CAL AND COMMERC I AL B OOKS . Compiled by EDGAR GREENWOOD . Demy 8vo . 224 pp . 1904. B e ing a Subj ec t-l is t o f the

Pr inc ipa l B r it ish and Ame r ican B ooks in Pr int ; giving Tit le ,

Autho r , S ize , Date , Publishe r and Pr ice . Pr ice 5 8 . ne t . (Pos tfr ee , 5 8 . 4d . home ; 5 8 . 6d . abr oad . )

HANDB OOK TO THE TE CHN I CAL AND ART

SCH OOLS AN D COLLE GE S OF TH E UN I TEDKI NGDOM . Containing par ticular s of near lyTechn ica l

, Comme r c ia l and Ar t Schoo ls th r oughout the Un itedK ingdom . W i th ful l par t icu la r s of the cour ses of inst r uct ion ,

name s of pr inc ipa ls , secr e ta r ie s , e tc . Demy 8vo . 150 pp .

_Pr ice38 . 6d . net . (Pos t fr ee , 38 . 10d . home ; 45 . abr oad . )

S COTT, G R E E NW O O D 8: S O N ,

TECHN ICAL BOOK AND TRADE JOURNAL PUBL ISHERS ,

RETURNTO the c irculation d e sk of anyUnive rsity of Ca lifo rnia Lib ra ry

o r to the

NORTHERN REG IONALLIBRARYFAC ILITY

Bldg. 400, Richmond Fie ld StationUnive rsity of Ca liforniaRichmond , CA c) 4804—46C) 8

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