THE SYSTEM

COPPER - SELENIUM

THESIS

submitted

for the

DIPLOMA

of

MEMBERSHTP OF IMPERIAL COLLEGE

by

C.MEALE, B So., A.R.C.S.

AUGUST, 1949

pit STE/PEA '!:341.4aum

AB$TRAVA

'be system copper - selenium has bins studied

by three main techniques, thermal analysis, X-ray

powder diffraction and chemical analysis to determine

the extremities of liquid miscibility gaps.

For thermal analysis, two cantina types of

set-up have been used; the one employing a sealed,

evacuated, ryrex glass tube for high selenium contents,

and the other au open crucible in an inert atmosphere

for high copper contents. kising these methods it has

been found possible to plot the liquidus curve for the

whole system with the exception of the portion 5c - 64

atomic percent copper. in this region the high

selenium pressure developed at the temperature required

to melt the alloys has been the limiting factor. Amu

here, however, the general shape of the curve has been

found.

ray powder diffraction has been used to identif; the various phase regions, and also to stud/ some

equilibria in the solid state.

'a a result of these studies, a neN aelenide

11, has been formulated, end the conditions under

U

Qt Cu2 Cala? 2 the first time,

era +allotted to ea

;40',010,1it Itirhi.imUCIun.

asoll,W1 AXIALIZI4 OF C4',4i,ed12 96016

kIXTURiw OR UwEVUNOSI.

SIOVION 11I $ A l'IMIKIDIAPY sunvey Or 'DRS 1? 29

TtM 4 L Afl3. (1) introduction

(2) A-ray equipment, and the general

18

character of the spectra

(3) Preparation of the two known eelonides

of copper to obtain tandax

diffraction patterns

(4) Preparation of samples, and the 23

interpretation of the patterns

obtained theretroa

TiCTIO0 DEUL‘VAUT AND AiaTigia OV MAW, 3 ,5 MUMS

(1) Introduction

30

(2) Iractical requiresOnts

(3) 4xnerimeata1 arrangements employed

(4) 1aUbration of temperature measuring

equipment

(5) ,ateriala used in thermal analysis

WkirNT; cont.)

lege tXii vt TKP, :Y6T4d Cue ,s. 56-73 (1) The low temperature method for selenium 56

and alloys of up to td.5,,;, copper

(2) The sealed tube method, 4-48.5 atomic 59 copper

(3) To determine the extent of the two- 65

liquid area

(4) Thermal analysis in the region 48.5 63 -

5C) copper

(5) As algnifioanoe of the halt at 377° 70

(6) :he system Je-Cuas, and the designation 71

of two-phase regions

-tf‘CUciii Vii fti4 ,3t,i2zAt Cu - Cu 4 74-83

(1) Introduction 74

(2) The miscibility gap in t system 74

(3) Thermal fosalsie in the range 1 95- 8,,)

copper

(4) thermal analysis between 68.R 4Ind

66.7:. soppier

82

.tXu Vlit Pk!:!VT1.? Cu At QtrAl 84-95

(1) Thersal analysis in this range 84

(2) ,"ensidoration of the phases present 85 (3) lability of tha, 2 87

(4) Non-stoiehlomotry of Cu 'e 92

' w.. QJf. SUD.·'.r:' (ooat; )., " ...• I .. ·•· H . "t .~. .•81 . • I b.J • . , 1 II ••

iilo:rlQN VIII. CRfrl'fALJ..Otli.A'ilY 0' 11'U f~J~~.ln.lij

~~.mO:'fJ.O~i 11:: D..U~S·1310.f

(1) A00UU7 of ..........,. ra&4e

(2) oone1.'.108 wi'•••• pftYlo...81;r

_.ded ..

Pq­,...U.JUlt-129

114

120

StNIPLIN

INTRU,INJOTION

:;e01Q.D LauwacTIoN

Copper haa long been available on a large scale

in a high degree of purity. in more recent years,

composition apeoifications have been laid down for the

various grades of the metal. ;Ielenium is one of the

impurities of which only a very small amount is usually

permitted. ro give some idea of the actual quantities

allowed, a few 4ritish eoifications may be quoted.

Lisi-1.1o58(1942) for 99.85A tough pitch copper, 6.o.109(1942)

for 99.754 tough pitch copper, and 3.,;.1172-4(1944) for

deoxidised copper slabs, all have a maximum tolerance of

:.02 x, selenium. Qonductivity copper for electrical

work sets a much lower limit on the selenium content,

and 4terica n si,ecifications of electrical wirebar allow

up to t.%. selenium ( J. newton and 0.L. Alson 'The

t-etallargy of keopper', liew fork 1942, p.221).

iien the final refining of copi;er is carried out

by eleotrolysis, this elimination causes no trouble, as

selenium is deposited iu the 'anode slime' along with

the precious metals. This slime is indeed one of the

chief sources of selenium. onlaso there is an aalple

sauna/ of cheap electricity, or unless the proportion

of precious metal in the ore is sufficient to defray

the coat, eleetrolysis is not an economic preposition.

airs-refining is then employed. Vas does net give

rise to any easy elimination. large {hodesian

cot,per deposits are almost devoid of precious metals,

and further, as these deposits are exploited, it is

understood that toe proportion of eelesiom is increasing.

Allis the elimination of this selenium Is likely to

become a matter of some imp-ort.

;41ston and WWI Oetkpat. 1,945,t14. 1934.)

claim to have secured such elimination using impure

sodium carbonate as • flux with blister Cr.oppe ihe

itish .;on-Ferrous )tals esearch 4seociation have secured up to fir.;, elimination using similar methods on a laboratory, scale. Jnfortunately, when tried on half

full scale, scarcely any elimination was noted.

borall (4111.2talle,1944,2435.) has shown

that selenium in copper La present as the selenide

Cu e. The known properties of this coavound were

not such as to enable easy explanation of the difficulties

of selenium elimination, and it wan in an attempt to

further elucidate the properties of the selenidea of

oopper that the ,resent inveatigiation was carrie0 out.

izeforence to the literature showed the existence

of three selenides, k„ 41 Cu 4e2. and Oue. of these

e has long been known, and was first prepared by

direct union by 4ierzelius (Ana.oblu.ot mat , Iec4,225,337; 1822*2 04,113.), and various methods of preparation and sundry chemical properties have been

studieu oy Amzes-lacon (4;ospt.I2aZ*I9,1411,127.),

iarkwann (mike& al (2)* 1862a/033309 :'abase ( n.

*him. et Lua., (6)*1887.1 535.), iAarelliCReo.tray. 242., 1923,4268M)* --veer and Atynaki (konatah.1924*

veillmen and rigge( eanorigsagi.* 1931,122,

375; 1933.2L.4373.)* and others.

Information on the physico-chemical properties of

the selenides is rather sparse and ill-assorted. In the

case of eu3 42* flahlfs(Z.phyaikhem.“6,1936,11015?.)

claimed to have prepared this by direct union of the

atoichiometrio proportions of the elements by fusion

in an evacuated closed tube, and to hew identified it

by its x-ray ponder pattern, although the latter al

contained some foreign lines. ;,'Ioria(.nszuchim ital

194,;,L,A461.) prepared the material by adding a

stoichiometric mixture of the two elements to a copper

sulphate solution maintained with stirring at 4000.*

and filtering off the product, and he found that this

decomposed at 17,°C. also suggested that it

belonged to the hexagonal crystal system.

Little (Ann 1,185941b2134) and Aargottet

(r.;osvt.f.rend., 1877,&1142.) reported the preparation

of e by direct union of the stoichiometric acaounts

of the elements. iierzelius (i.e.) reported that ou

heating in air, Otiie lost half its eelenium, and

AinzeswAaoon(1.2.) stated that at dull red heat

tAr42, welts.

u e hau been somewhat more extensively studied.

The amervstion first made by Hittorf (42.a& nn 1851,

8k,1.) Chet Cu e had en electrical conductivity of

alsoat 'metallic' nature* has (:iven rive to considerable

interent id its structure. evey .$1923,21,

.) and Huggins (ibid 211.) considered that Ou, 'e wen

cubic, and of the lantifluoritel type, having a parameter

of e05.75110. A ilartwig (4 '4-riot $1926,64.5 3. )

using the natural mineral Serzellanite found the same

structure, but with a05.7461).400. gehlfa (1.a.)

mode a thorough study of this eubie fors which exists

above a transition point of llo°Q. Oellati and ,Lusane

Oysik.hem.,189,2282.4 and found, usiuG u high

tiNDperature caiaers, a modified ,antifluorite, type with

four 'llobile* copper atoms positioned interstitially

in the lattice, iea also showed that the compound could

exist with a copper deficit, giving rise to a non-

otoichiometrie range. -1,ahlfs gave X5.8 );t° for the

parameter of the stoichlometric compound.

and .0hring (; hysik A;hem.0.1937,j0,A221.). as a

result of conductivity measurements. considered that

this noo-stoichiometric range extended to 61.5 atomic

percent copper, and auggested that the form existing

below llo°Q. was tetragonal. Jorchert ( 194).

1;2.54.) indexed this low-temperature form of Cu e as

tetragonal with parameters am11.49A°, ca 11.72':°.

also shooed that the transition temperature 6is

depressed by a copper deficit as compareo *ith the

atoichlometric, reaching cC. or below at 64.3

stowle = copper.

he only investiikations ode on he copi;er-

selenium system have not resulted in a complete picture.

i4labon (pompt.rend..1912c154k1414.) studied the e.a.f.

of the cell Ou/CuW /0ye, and found that the only

selenide occurring at room temperature 4ms. ,,:;u :es

attempt at plotting an equilibrium diewram was made

by wriedrich and Leroux Getailurgie.19LiS.1,355.) using

the classical methods of thermal analysis and microscopic

examination. •-wing to the volatilit of selenium,

theae obrkers were forced to oonfine themselves to

the eystem 0t-Ca they used an electricall carbon

resistance furnace. „44 containing vezeel for the

alloys, a fireclay crucible wee used. ,he lid of

this had a hole through which passed a plat/twee-

platinum/rhodium thermocouple. :'hie latter was

protected by a thin silica sheath in the melt. -xternally

the thermocouple was oonnected to a millivoltmeter, and

by means of a calibration curve obtained by taking

melting points on standard meteriala, the voltmeter

readings were converted to temperatures. The crucible

gias placed in the space between the carbon rods.

r.iedrich end <reroax found that the r.-u-Ou2 e eutectic

was at x.: 3°s and about 1.5 selenium composition.

,hay found a miscibility gap et 11 4PC. extending for most of the range 1.5e-33A selenium, the exact boundaries

being unknown. ;he melting point of e wee found

at 1113°C.

In view of the complete ebsence of date for

solid-liquid equilibria in the system tillers-oe, and

of the bonsidereble period which had elspaed since the

observations on the system ta-Cu ,e were woe, it was

.7.

felt that any investigation into the physico-onemical

properties of these Belem/des should coumence with a

study of the equilibria existing in the binary systeol

e. Olis therefore, was taken es the subject for the

present work.

ale state of the eopp4r-selenium system is

typical of that of a considerable number of metaly

selenium systems. The equilibrium diagram hee been

plotted from to about 3c4.- selenium, and no further.

she reaeon for this is not difficult to find. Awlenium

is 41reciably volatile below the melting point of most

of the common metals and their normal valency selenides.

hen the amount of saleatua present is lees than that

required for the formation of this normal eeleniue,

this is formed at low temperature, before any selenium

can be lost by volatilisation, end tae selenides are in

the main thermostable. 4ben, however, there is an

excemi of follenium, this is lost by volatiliziation,

and as well as the very considerable attoc4 of any

metal present, the range of composition which can be

reached, aud the accuracy with *Atm this can be

deter ineu are both restricted.

in the course of the investigation to be carried

out, the methods employed will be those so extensively

used in the past, namely the claa!,;1cal thermal

analysis to fix the solidus and liquidus relations,

and ray powder diffraction methods for transformations

yithin the solid state, and also for indentification of

the phaes formed.

It is inevitable that in the esployment of ouch

igethods, it will oe neeesaary to analyse samples-for

both copper and selenium, and it is therefore desirable

to preface a more deteiled consideration of the .1.;hods

used, by some remarks on the itethods and accuracy of

analysis.

Li

0 LYsiz, (410 .evica 00 AUWiiir 1N mixfJus ua 00aPi4U3

1 study of the literature fled to reveal

any specific metbods for determining both copier and

selenium in presence of each other. number of

analytical procedures for determining selenium in

seleniferoue copper were available. In the main

these thethode did not permit of ready coAter determim-

ation, and, in some casea, failed even to provide a

separation of the constituents.

The problem was therefore broken down into its

(i) dissolution of the material.

(ii) separation of copper and selenium.

(iii) determination of selenium.

(iv) determination of copper.

i these, the second is the most important, and it is

pecessary for the first, and to a lesser extent, the

third and fourth stages, to be subservient to this

separation stage.

Information on separation xas obtained froa

several standard textbooke of Wantitstive analysis

among which may be mentioned P.P.Treadwell sat wia.Hall

'Analytical .11e:Aistrj'' vol.11 Ass lark 19300#

A.1debrand and :4., Lt.Lundell ( Wiled Inorganic

Analysis.° New ,:ork 1929 ), and ..R.chbeller and

owell C'snalysio of ingrals and sues of the

;.arer lements.' iondon 1919.). choeller's method,

like those devised for seleniferous copper is

ansaitsble for any but very low percentages of selenium,

and is consequently quite unsuitable for, use in the

oresent work, where a very wide range of relative

proportions way se encountered. :room both the other

sources a sethod of separation was obtained envoivinK

the precipitation of seleniu=t as such from a solution

of a selenite by some of the weaker reaueing agents

in presence of concentrated hydrochloric acid. Thus

it is necessary that the dissolution process should

produce, or be eapsble of produciug, a solution of a

selenite.

this may be accomplished by use of an oxidisis

fusion giving a selenate followed by a reduction of

this by boiling with hydroehlorie acid until no further

chlorine is evolved. An alternative is a nitric sold

dissolution, but the presence of an excess of this i8

undesirable as precipitation of selenium is then

incomplete. solvent said to be efiective for

selenifexous copper by (sual st 1942,iZ,186.

1—

sod used by i-ollard (Analyst, 194b,7, 1.) in his

determination of selenium in selenifercus copper, is

bromine in hydrobromio acid.

'vials were ;lade with pire selenium usin this

latter solvent, but it aas faun, to be very slu6gish

in action, rind the recoveries of aelenlum on subsequent

prec4itstion Ath sulphur,-dloxide—ohturated hydrochloric

acid, filtration on a tared sintored glass crucible,

wishing end drying, vere not concordant. The probable

cause of this ie oxidation of a little selenium to the

sexavalent state, whence it is not reduced by sulphur

dioxide.

6ruckner, ja.la 19339 s 3,:i5.) has made a systematic study of the coQpletion of precipitation

of ,,ieleniam by sulphur dioxide and hydrftsine in the

presence of various acids. Ali showed that while

precipitation was incomplete in presence of nitric sold,

sul huric acid did not have this adverse effect. it was

also found that after fuming with sulphuric acid for as

'cog 4e one hour, no loss of selenium wi'is apparent. Ala

opens nu the passibility of retzovins excess nitric acid

by evaporating to fuming with sulphuric acid, and then

precipitating the selenium in the usual way.

hit this 1:lethod of nitric acid elimination

-12—

involves a sowewhat lengtny procedure, it has at

Least the decesary reliability as is shown by the

following testa. weighed quantity of selenium

was dissolved by 4arming in lo ml. of lt1 nitric acid,

and. 15 al. of 111 sulphuric acid added. The whole was

heated on a sand bath until the latter just fumed.

15rJJ 01. of water, and 3 al. of hydrochloric acid were solution

added to the cold basin, and a hydrazine hydrochloride

added dropwise to about excess. the precipitated

selenium was filtered off, dried and weir hed.

eight of selenium taken 1432g. .2A7g.

eight of selenium recovered Q.2A96.

.'ercentage recovery 99.6 1..1

thus a method of determining selenium is available. he

next step was felt to be to test the separation obtainable

*y this precipitation.

for this a copper-selenium mixture was i,repared

by dissolving quantities of about one ;rs:,5 of each of the

elements in 15 ml. of 1;1 nitric acid. the solution was

made up to 250 ml. in a graduated newt, and 25 ml.

portions used. the selenium was ueteraine6 in the same

way .As before. n the filtrate copper was determined

volumetrically after adding an excess (5, ml.) of nitric

acid to destroy any hydrazine present, and re awing

-13-

°chlorin acid by evaporation to fuming; with the

sulphuric acid already present. 5g. of potasnium

iodide were added, and the copi-er liberated iodine

from this. 010 ioOine was determined in the usual way

using a standard sodium thlosulpnate solutiou, enu

adding starch as indicator. ,his method is very Nell

known, end it W60 not considered necesstiry to teat it.

the results obtained are shown os follows.

'eight of copper taken 1•3326s.

eight of selenium taken 1.5325g.

Lr:ede up to 25,) ml. 25 1 portions used.

ii

Atight of selenium recovered ....1527. J.1533g.

Vercentae recovery 99.7 0.0

Velure of 0.1031s . thlosulphate

eercent copper recovery 14„J.1

Ibus a satisfactory separation had been effected.

o-precipitation of copper on selenium is more

likely to occur when the proportion of copper to selenium

is high. mixture of over copi.er was prepared, and

tested with firstly one, and secondly two precipitations

of selenium, the first precipitate being redissolved,

and again precipitated, and capper determined on the

united filtrates.

eight of copper taken

.,aide up to 2501.

2188g.

2.2020,

al. portions used.

eight of selenium taken

eight of selenium recovered:--

(1) cue precipitation 0.C.44391$•

(ii) Two precipitations o.o4pg. Percentage recoveries 100.1 and 99.9 respective,.

Thus no reprecipitation will be neoessarl when the

percentage of copper is less than ninety.

The whole procedure then become as follows, the

first ox Lionthereof being based on that of iiruckner

for seloniferous pyrites.

Aifficent of the sample to give a convenient

weight of selenium 0.1 - 0,5g.) was weighed into a

porcelain basin, end Lag. of 1.1 nitric acid added.

the busin was warmed until no sore nitrogen peroxide

Was evolved. At this point an undissolved scum usually

remained. 5m1. of hydroehlorio acid were then added,

and the basin again warmed on a sand bath. Ater the

scum had dissolved, the basin was allowed to cool, 15 mi.

of 1:1 sulphuric acid added, and the contents evapo vted

until white fumes of sulphur trioxide showed that all

the exees nitric acid and hydrochloric acid had been

-15-

eliminated, ,hen cold the contento of the basin

were transferred vantitatively to a *1.. beaker,

d 5. al. of bye rochloric acid and about 2.,;u m1. of

hot water added. ,4th the contents of the beaker

aaintained at about 00., a 1,);, solution of hydrazine

hydrochloride wes added dropwise with continual stirring.

An estimated 1; excess of thio solution was audeu. fhe

whole was then kept warm Lor an hour, during which time

the red selenium initially precipitated turned black,

and became more crysoalline. This was then filtered off

on a tared sintered glass crucible, washed with water,

alcohol and ether, and weighed after drying at 10C, for

45 minutes.

the filtrate was evaporated to ca. 5J mi., and

25 ml. of nitric acid added to destroy excess Aydrasine.

Vhe whole was thee evaporated to fuming. hen cold a

sodium hydroxide solution was added until a basic

copper precipitate was just formed. dais waft just

redissolved with 2U sulphuric acid, end 1-2g. of urea

added. 4fter boiling for ten ainutes to remove the c

lest traces of nitrous fumed, a precipitate was firer 04

After cooling this was dissolved by adding 15 ml. of

acetic acid. 3-4g. of potassium iodide were cubed„

when iodine was liberated. standard thiosuiphate

solution was was run in from a burette, potaseium thiocyanate

being adaed near the end point to liberate iodine

adsorbed on the cuprous iodide precipitate.

.several modifications were made to suit various

relative proportions of copper nnd aoleniva. hen the

percentage of copper was greater than ninety, the first

selenium precipitate was dissolved iu nitric acid,

reprecipitated, and filtered off, and the two filtrates

aniteu. rhis obviated the risk of copper being adsorbed

on the selenium. in oases where it was convenient to

have less than the total copper for titration, the

solution was made up to 250 wi., and 25 or 5,:) ml.

portions wove. here insufficient copper was present,

it was found desirable to increase the weight of sample

teen so that the weight of the selenium precipitate was

vs great as lg., but there was an obvious limit to thole.

ourther examples of the accuracy of this

aaalytical method may be found in cases in the succeeding

work where duplicate analyses were run, and where it was

found that these gave results concordant within a

reasonable experimental error.

pFyta..vaNtin auavia ci; LkU12.16 JSIAI3/ RAU.

-17-

3ACT1Os III: A PRELIAIIARt euFArs'L OR Titi StMeigi 0.,ISLI X-RAY'

Si) Introduction.

The use of ray diffraction methods to supplement

information obtained from thermal analysis has resulted

in a greatly increased knowledKe of the phases existing

in the solid state in binary systems.

:mull (J Amer 'hemi,',oc. 1919,41,1168.) pointed out

that x-rays provide a method of analysis of crystalline

substances, es each has a perfectly distinctive pattern,

nod a mixture shows all the patterns of its constituents

provided the asounte of aeon are sufficient. in

a two component system, each two phase region can be

interpreted in terms of its constituent phases provided

the patterns of these are known* A new phase may be

considered to exist when the pattern of a sample is

simpler than both the adjacent patterns. it is possible

not only to identify the components of a mixture, but

also to make some estimate of the proportions of each

from the two patterns. .uch an estimate is only empirical,

but by using etandards of known proportions, may be made

to within 5S.

,.of the main types of h-rAy photograph, single

crystal oscillation and rotation, and •sowder, the last

in by far the most adaptable to the needs of the present

-18—

research, am was used throughout.

be operation consists essentially of passinq

a monoshromatic X-ray beam into a powder, or more

accurately a collection of small crystals, of the

materiel, which crystals are continuously rotated.

Then in the iraKg equation ni\m2dan for the

diffraction of a wave front at a surface, where A the

wavelength is constant, crystal planes of the same

family, i.e. with the same spacing d will only reflect

for the same value of 14, and will consequently give the

same reflected beam. tact different fauily of planes,

since it has a different d will reflect for a different

value of 4, and consequently the diffracted beam will

be in a different position. Phua, each chemical species, having its own set

of spacing, has its own characteristic pattern, different

from those of other species, and thus identification of

substances oan be made without knowleutift oi their crystal

structures.

eialecent VAIALIVAMIcalaract--._-_ELRE12121 spectra

The set used for the production of X.-rays was of the continoouslp-evacuated tube type supplied by

-19-

fetroit:olitan Vickers Qo. This comprises essentially

a beaten tungsten filament maintained at a high

wotential, and a watercooled earthed anticatbode.

The electrons emitted from the filament are focussed

on to the anticathode, and their high velocity produces

v-mays from the latter. The anticatbode or 'target'

can be changed, and eith a selection of metal tarbets,

-rays of a wide wavelength range can be produced.

the cameras used were of 9- and 19-cm. diameters,

and were of the type designed by Jradley, :ipson end

zetch 61. ci. Instruments, 1941,18,216.). This type

consists of a slit system to limit the width of the

beam to 1-2mn., an arrangement for holding and rotating

the specimen, and a clip to hold the film in place. The

whole is on a light-proof base, and has a light-proof

cover through which the X-ray beam enters, and the

'straight through' beam leaves, both apertures being

covered with black paper.

40etmens wore made either 4y rolling into a rod

about d.3mm. thick with moist gum tragacenth (ooksby,

J11.2. ..21. .u32,1942, 1i, 673.), or by sealing the

powder in Lindemann glass capillaries; Lindemann glass

iaz a lithium borate glass of low scattering power.

, ..an the film, the actual lines of the pattern

are superimposed on a certain amount of background.

this la due partly to scattering of the 1-ray beam by

the specimen, and partly to X-ray fluorescence. if the

si;ecimen is of a material of en atomic number imedistely

below that of the target, this fluorescence assumes

considerable proportions, and it is for this reason

that the variation of target is of especial sae. A

ohange in the wave length of the x-rays used only afflicts

the pattern in so far as an increase causes spreading

of the lines in the pattern; a decrease causes the lines

to move closer together, but brings adaitionsl lines

into the 'high-angle' end of the pattern.

(Iii) k'resaratioa of, the , two,known selenides of eoRper

to obtain standard diffraction patterns.

The first step to be taken in an investifottion of

the system was oonsioered to be the makiog of a general

-ray survey throughout the whole composition range of

the system. Fox' this it was necessary that patterns of

both ehe elements and of both the known selenides, Cu se

and Cu :e should be available. Thus it became necessary

to prepare these selenidee.

The method chosen was that of Oeillman and riK,E e

-21-

an,_ obstise 19314E075; 19339312.373.), consisting of the reduction of copper selenite laud

basic copper selenite by bisulphate in neutral solution.

.crystalline copper selenite wao prepared by

treating copper sulphate in solution, with the

theoretical amount of sodium selenite, filteriol, off

the amorphous precipitate, and warming it in water

until blue crystals of the iithydrate were aeen. these

were then filtered off, washed with alcohol and ether,

and dried at llu°C. The basic selenite was obtained

in a non-orystalline form with varying amounts of water

by adding to a copper sulphate solution the theoretical

amounts of sodium selenite and sodiva h droxide solutions

in such a way that there was at no time a large departure

from the selenite-oaustic soda ratio as required uy the

equation

t4a Ag) 20u8O4 2Aa011 CauCIL:e03 2Na rAtu

for the actual reduction to the selenides„ about

.5g of the selenite or basic selenite, together with a sodium bisUlphite solution containing about a 20k excess

of sulphur dioxide over that required for the reduction

acoording to the relevant equation, either

w;e03 3S0 3H 0 m 3HC04 + Wee

Or Or CuSe0 41i 10 u Se

2-

was placed in a stopi;ered bottle, and waintained,

with constant agitation, at 91)C. ( on a water bath

for about four hours. MA, black sel nide was then

filtered off, washed with alcohol and ether, and dried

at 11 :.,o _

AA sis of these selonides resulted in the

following figurest-

Cu

oieight of ,41enide taken :1.2712g. 0.250g.

eight of selenium precipitate c...o961g.

-eiqpht percent selenium 39.27 39.23 Volume of ,41768A thiosulpha e used 13.2:.; x1.

eight percent copper

ratio Cu;f-At 1.92

Cute

eight of aelenide taken 1862g.

eight of selenium precipitate 2g. ,.3.1326g.

.eight percent selenium 54.78 54.36

Volume of 0.1768g. thiosulphateused7.37m1. 9.55mi.

eight percent copper 44.49 44.41

,o1. ratio i.41;'3e

Xvrvy diffraction patterns of these two selenides,

and of elemental copper and selenium were tatten on a

9-an. camera.

-2 3-

(iv) evaporation of envies,L end the intevretation of

the eatterns obtained therefrom. iith the above mentioned patterns availeole,

coppereselenium mixtures containiue roughly 5,1e,15, etc.

ntomic percentages of copper were eade up, and sealed in

evacuated ere glass tubes in the following manner. :Che

tubes were closed et one end, and drawn down to a

constriction about 7

from the closed end. A quantity

of copper was weighed by difference into an seate mortar,

and the weight of selenium required to give the desired

pexcentage calculated. eo near this amount of selenium

as possible - erring on the side of exceee wzn weighed

on a tared watchglasn, and trensferred tnenoe by means

of a camel-hair brush to the rtar. he watchglass

was then reweighed, end the difference in weights gave

the welght of selenium actualle taken. in this way it

was found possible to weigh quantities of selenium

within about half a milligram of those desired. The

two components were then ground for ether is the mortar.

'the characteristic colours of the two components soon

disappeared, but erinding wee continued for a aonsieerable

period after this had occurred. he mixture ArtiS teen

transferred from the mortar to the 1;1Rus tube via. a

piece of yellow glazed paper and a funnel-shaped tube.

-24-

n all cases trannfer was made S6 com lete 6B possible

by the use of the csael-hair brush, ;he total 4eiOt

of etlxture preparAd so arrsakied that the whole was

used in the tube, and that the proportion of the tube

apace loft unfilled was as small as possible, thus

keeping to a minimum the risk of sublimation out of the

bulk of the material. In this way the actual proportion

of the tact constituents in the mixture used is not

dependant solely on the homogeneity, i.e. the thoroughness

of alxiri by pyrex tubes containing the

miytures were connected via a trap to a iyvac rotary

pump. he syetem was evacuated up to the mixture-

containint4 tube, where it was closed 01 a sore clip.

.4- means or the latter, the air in the tube was very

gradually renoved in such a manner as to avoid disturbance

of the powder. . hen all the Hir haU deerl removed, and

the vacuum appeared to be hard, pulping was continued

for about five minutes, after which an air-coal gas

flame player round the constriction in tae ;:yrex tube

was auffioient to soften the glass, when it was it .,iedietel

sucked ia, and a oeal effected.

.41 he tubes neva slowly rained to 404 0., and

maintained at that temperature for fOurty hours after

which they were allowed to cool, and broken open, end

the contents of each thoroughly ground in an agnate

mortar. i sample of each was then made into a specimen

with gum tragacanth and subjected to x-ray diffraction in

9-cm. camera. she patterns obtained were interpreted

in the liht of knowledge of those of" co.potr, selenium,

4.: Clave. interpretation ws.J3 made at this stage

solely by visual cospariaoh. the low angle knife edges of

films to be compared were laid alongside one soother, and

the positions of the stronger lines noted. bile this

method is empiricel, in cases much as the present where

the number of patterns to be consit.iered is limited, p,nd

thewe axe entirely distinctive, then a reliable inter-

pretation may be made. he results of these comparisons

may be seen in the table overleaf.

To study the change from Flu to which change

appeared to be eharp, the region 65-7rd at A of copper

vas covered at one percent intervals, the samples being

heated to 4.Ju Q. es before. The interpretation is

shown overleaf.

• copper iIkttera no. in„erpre ation 11140011.1...gorArr

7.8 173 se, nothing else

12.7 174 SO, s:126

15.6 175 lie, 01:30

19.3 176 409 CUse

25.4 177 8., Ouse,

3,:46 178 .ie outset

36.6 179

42.1 18(.;

44.6 181

5).9 182

53.4 183

59.4 184

65.2 185

7u.6 186

73.4 187

81.9 188

85.4 189

19

95,6 191

uAt, somo .e, J'

• e, some e, strongest

Cu little

7.e

eu 0e___ (complex

Al 13

Cu, little

04 • &rid were phases not previously described.

Cu 04, Izixed

6?.0 fl only

68 2 only

69.0 only

only

As B appears to exist at a composition of Cu pt it was

asauwed to be a fora of Cu 6e. This has since been

reported by $orchert 4rist 1945,L;60; vAa9

42

in an effort to elucidate the nature of

bud

mixtures of 59- and 4u-steJ;; copper' these being the points

at which the lines of the respective phases appear=?O to

he at their strongest, were bested at 25 ° 0 for 9;: hours.

lower temperature than previously was usaO to avoid the

ossibilit of the T,;,.resenco of decoaposition '4,roducts of

the phases under consideration. tha 53 pattern

contained lines of ou2 e, ClOe. and end was not a

pure phase. The 40,i, pattern shooed no lines of CIL e, and

was pure searing in mind the tendency (J. Tlume-

t-iothery, ,11 ,,tructure of :oetals and Alloys", 1,onuong1444.

of copper to form definite compounds with sub-40up

-33-

metals such as elenium, this was designated Cu

mad hmd not been zreviously reported.

qle only ;7reparations of in the literature

are those, of Yehlfs , Aaysik. :hem. 1-936,21,157. ),

and 'oria (Jazz. him. ital.. 194.; 7:;,461.). ;4h1fa

used direct anion at lit* •• but oria states that

ca7le2 decomposes at 18000. the 1:attern of 58,

copper heated at 254"0.was of a composite nature, and

',A123e- a com;,ound more rich in copper that: Ou3 e2, while the original matorial was less rich- was present, it

a8 conuidered that decomposition of;113 e2 ( ) had

occurred at this temperature. In vie* of this, ,;oria's

method was uaed to obtain the material. 10 1 .ueml. of

a W. copper sulphate solution, 2eg. of a mixture of

cope and selenium in a 3:2 atomic ratio was added.

Ewa drops of a se dace active agent (tPergitoli) were

aeded to CE,480 Aettins of the eeleniva, ;he whole rase

stirred and dept at mow. tor 15 hours. The product

was filtered off, eashad with alcohol eno ether, and dried

in a eesicostor. i 9 oak. A.-ray. diffraction pattern

wara similar in so far am could be ECen, with that of

.aria rho gives no nua,erical este and only a poor

reprouuction of the pattern. C*omparison with patterns

of around ti at.; copper showed that the latLor

contained Cu :e in addition to the lines of P:u

and that Cu,2e had partially decomposed, r fir:

decomposition la fartaer consioared in a later section.

malimis of the prepared material showed it to Ile

59 e' thus it seems that the only phases likely to be

encountereo in the aystem are Cu2 Cw.le, Cu ,e end

',Axve3.

~~ia!i:I5! l'._.....l~j'• •

'If! ttl ••

Ayst.elitStAfit

AliAllf31$ TKORS2411taf.

(i) 4,qtroduction.

Wring the half century which has L'vesed since

the inception of thin mode of investigation by . eville

and 'esicock (see pai:ers in ;. ,-;hest. inc. a ltAal ),

great use has been made of it. Indeed, i t is doubtful

if any other ainsle method of stud., Ina been so widely

used. vne result of this is that it is now almost

impcmsible to assign to any individual worker oreait for

any specific part of the equipment.

The accepted requirements of a satisfactory set-up

have been listed by u.a. Oesch ( etallosraphy. ,ondon

1937.) as beings-

(i) elting to take place under conditions such ns

to avoid contamination.

(ii) ,.,eating and cooling rates to be controllable.

(iii) l'omperature to be measureable with the xeluired

degree of accuracy.

A ormal.

(a) Airnaces. A-ractically the only method of

heating employed la the electric furnace. This is

usually of the wire resistance type, Out rod resistances

-31-

have been used, alai when available the induction

furnace is ideal.

hen a resistance furnace is used, cooling is

usually effected merely by turning off or reducing the

current. he resultant radiation heat rossea cause the

cooling rate to vary. Lb obtain a uniform rate of

cooling, the current may be continuously reduced by

means of a motor. ,Ilato (2. AveU. 1940,&1 721.)

and i:osenhain (J. Inst. ;Nets,,, 1915,12,16,.) used an a gradient furnace eonsisting of a vertical tube with only

the top quarter pound, and cooling was effected by

lowering the material at constant rate out of the heated

zone, Ilia type of arrangement is almost impossible to

use when a vacuum or inert atmosphere is being maintained

in the furnace tuba.

(b) efractories. ehe choice of refractory is

governed by its resistance to chemical attack, and its

strength at the higher temperaturea used, ,kt quite low

temperatures Irex glass ie suitable for quite a wide

range of materials, and at higher temperatures fireelay

crucibles are widely used provided the material under

investigation is not such a strong reducing agent as to

attack silica. Aar furnace tubes alumina is much used.

Alice is invaluable, but tends to become permeable to

;pace s.t temper&tares above laermo—couple

sheaths azd other tubes must be impermeable, and below

15 fireolay is usually used.

(c) i-yrometers. Three Wes of pyrometer are

available— the thermoelectric couple, the optical

pyrometer and the electrical resistance pyrometer. of

these, the first is by far the most frequently used. The

wires must be highly infusible, and unaffected by hot

sir. she moat used couple is one of platinum againat

a platinum—rhodium alloy containint; 13 of rhodium.

the V. Ili. 1. of any couple is given by

Saba+ b d am'

where .1- is the temperature. the best method of

calibration is by means of a number of fixed points.

:he uilplest method of meestarinK the rye. F. is by

direct readins on a galvanometer. fotentiometric

methods are also used.

(d) curvet]. .echanised methods of

taking eoolinv: curves sre often used. 4nverse coolin6

curves are much used as they show up changes of direction

more readily. vhese curves were first used by ,osenhain

( roc. s. oc. 19Q8,21,61.) and plot the time re ;aired

to fall through a given temperature interval against the

temperature. hide this type of curve has the advantage

-37

that it does not require as such space as the direct,

it hen been pointed out by:flume-f;othery (J. Inst. ,,etal

1929•.3)97.) that the ultimate sccuracy aust depend on

that of the temperature measurement. :tooling curves are

uncertain for changes within the solid state, es usually

only email heat changes are involved.

(a) 1-urity of materials. Rosenhain (J. Inst. gotals,

1929,42,31.) has pointed out the neea for using materials

of high purity. 3:his is possible when high purity

material is available commercially, or when the nature

of the impurities makes purification fairly simple, but

fallin4 this the purest material available must be used.

‘'.pecial for more reactive ana volatile materials

Hume-othery Q. in aitnls, 1928,44.4650 has

listed several adaptions of the usual experimental set-up

for uae with materials of this nature. une of these used

by Jenkins (J Inst.soetals, 1924,2,42570 consisted of

a device whereby the material in question was melted under

a pressure of inert gas, but this is only satisfactory

when the degree of volatility is fairly low. In eases where the volatility is high, the method of ..aneuri (J. k;hem. :oc. 1923, , 2141 1922,121,2272.) seems to provide

some sort of solution to a difficult problem. 'his method

consists of using a sealed evacuatea tube of iyrex glass

or porcelain to hold the material, ano attachin the

thermocouple by means of a wash of cement to the outside.

The obvious disadvantage of this is that the thermocouple

Is situated far from the centre of the mass of the

material.

recant jeers the practioe has been introduced

of using bones of some strong and resistant material

such as chrome steel. f.racek (-rens. Amer. , epRhxs.

Union, 1946,?2,364.) used such a bomb, rind inside it es

containing vessel a silica tube. 4=pressure of carbon

dioxide inside the bomb serve4 te neutralise the effect

of the estimated pressure fenerated in the silica tube,

and thus prevented bursting. This i* undoubtedly a

much more satisfactory method, but unfortunately needs

a considerable amount of specialised equipment.

(iii) o.xperimental arrangtLacuts employed.

_elenium la of course quit* volatile at fairly

low tenexatures, having, according to irininer and

'iruCkmoller Waik. k hem. 1912,81,129.) e vePeur

preasure of 3mm. at 592Q., 42 m. at 5eQ°C., end 7Efeem.

at Eid2k:4 it is not surprising, therefore, to find

that very few metal—selenium binary systems have been

studied in any except the low selenium content regions.

here the selenium combines with the metal at a low

- 35-

emperature before any apprecieble quantity min be

volatilised, and the resulting selenides are, in the

main, thermosteble.

There hoe been only one investigation of the

copper-selenium system - that of ,,Viedrich and a,eroux

Q.. 0.) and this covers only the region 0i-Ou e. ihie

was carried out in an open crucible using a platinum-

pletinua/rhodium thermocouple protected by- a sheath,

and an atmosphere which was effectively carbon dioxide.

these workers report considerable volatilisation

at the selenium rich end of their range, it is note-

worthy that they succeeded in preparing a melt which,

after thermal analysis showed a composition of 33.+ at.

of selenium.

chus while it should be possible to repeat this

work in an open crucible, it wan considered that all

eork et higher selenium contents would require closed

systems.

(1) ,Ten crucible arrangement. The furnace used 485

of the type heated by resistance reds and is sholao in

fig. l. :our olobar. eilit rods designed to take a

Inc ximum of /a volts, and to attain a teaperature of

Wio°0. were spaced equidistantly round parallel to,

and at a distance of about two centimetres from a vertical

FIG. r

FURNACE TUBE

NICKEL CONNEC TORS.

°GL.023A11'

Fl 15 K

LADS.

T,

RP

PLAN

VIEW

silica furnace tube of about seven centimetres

diameter. The latter projected top and bottom from

the surroundingAFY refractory firebricks, and the

ends were cooled by water-carrying 'comp' tube coils.

This arrangement together with firebrick 'radiation

stoppers' enabled rubber bungs to be used to close

both ends of the furnace tube without risk of pyrolysis.

The upper 'radiation stopper' was suspended in a

nichrome wire cradle from four hooks on glass rods

carried by the top bung.

Vhe heating rode were supported on asbestos

sheet some 5cm. below the iron sheet supporting the

refractories, and the depth of the latter so arranged

that about 5cm. of the tops of the rods also projected.

hus there was free circulation of air around the ends

of the rods, and this together with the fact that the

ends were metallised to some extent combined to keep

the junctions with nickel strip leads comparatively

cool. The rods were connected in parallel to a ,Jresham

variable voltage transformer.

Temperature was measured by a standard platinum-

platinum/13rhodiusi thermocouple. :his was connected

by special leads designed to compensate for the

emperature of the 'cold' junction of the wires, to a

-37-

Qimbridge Instrument :o. millivoltneter the scale

of which was calibrated to read the temeerature

directly eith such a couple.

,s containing vessels, fireclay crucibles

were used. these oiers capable of holding about 5u-6i g.

of copper turnings.

or an atmosphere it was decided to use nitrogen

as neither cop er nor selenium nor any of the known

aelenides of copper are attacked by this gas.

few preliminary experiments were carried out

on copotr to discover with what ease oxidation could

be avoided. crucible containing itieg. of copper was

supported in the heated zone of the furnace tube by

firebrick. tight bungs sere fitted, and the air

in the tube removed oy a 'h vac' rotary pump. Atrogen

from which any trace of oxygen had been removed by

passing it over a closely wound roll of copper gauze

heated to 852C., was then slowly admitted to the

furnace tube. This pus ing out,. and the admission

of nitrogeu was repeated, and a slow stream of nitrogen

then passed through the tube for about half an hour

before heating was commenced. -he copper was than

melted, and retained in that state for half an hour,

end then allowed to cool in the nitrogen stream. ,:hen

cold the ingot was examined, ono cut through, and

while all ht oxidation was evident on the surface,

the interior showed no obvious signs of attack.

In view of the fact that Lhe re oval of Kee from the

furnace tube i)rior to the admisAon of nitrogen was

probably not complete as no manometer was in the

system, this was felt to be quite satisfactory.

As a preparatory to the determination of melting

points, and as a result of the above testa, several

modifications were made to the apparatus. J5cygen-freev

nitrogen from a cylinder was used, and was dried

through concentrated sulphuric acid, and .paseed over

the heated copper gauze roll to remove any trace of

oxygen. ,s a measure of the low oxygen content of the

nitrogen, it was found after ruanin4; the gas current

for two Egontha that only very alight oxidation had

occurred at the entry end of the roll. lie gas train

is shown in fig.2, where it may be seen that after

deoxidation, a two-way tap (A) permitted a selection

from two paths to be made for the nitrogen. These two

paths later converged by means of a two-way tap (J)

connected in the ()posit. sense to the first. Qf the

two paths, one (1) was connected to a Liercury manometer,

• T H ER MO{OU'PLE •

1rT-t-----r"T"T"!1 Po l"D IA -r,0 N5 T JPPE R

I NICHFWME.---ti -- l--SUPP OA J _-)

f-I

I THE~MDC.OUPJ,.E

\

MANOMETER

A :.. l.1 N D :J t- , 5 A5E

PL u (,.

tTD PU M P

TRAP

CRUC. IBL E

UTYLPHTHALAte

VALVE

F IG.2.

N ICH"ROME - w uUNDFUR NAC.E.

( ~S-O ~_J _,--- -

TRA P

N%,.~

FROM( YLlN P £ 'R

end the other{ii) incorporated a safety velve no

that ohon the ereseure of eas was greater than

stmoepteeic plus about 7cm. of dibutyl phthalate, the

gee escaped by bubbling through the phthalate. lae.

nitrogen then in the reconverged paths was led into

the top or the furnace tube via the side as end one

end of a T-piece, the thermocouple entered the tube

straight through taxis je-piece, and a vacuum-tight seal wee maoe by means of 'picein' wax at the point where

the couple emerge into the air. i tft vaci puap was

attached to e tap carried by the bottom bung o the

furnace tube.

rho operation CO fa es the atmosphere of nitrogen

was concerned then beoeme ae foiloes. eitroeen flowed

through (;) into path (ii), and since (;) was open to

U). the gas escaped threuoth the valve. he tap fro

the ' .iyvac' pump was then opened, end the air in the

fernace tube pumped out. ehe gesnometer in path (i)

provieed an indication a$ to when this was co:t elete.

e-camp vas then cut off, and C) turned to coaeunicate with (1). `Vhie was done carefully in such a way that

the entry of nitrogen into the vacuum was slow and

Aentle. ,itrogen Has allowed to pass into the furnace

tube until the manozeter showed that the iressure

therein was st °spheric. The pumping out and admission

of nitrogen was then repeated toice. 'hen heating was

in progress, (A) and (4) were both open to path (ii),

and a slow stream of nitrogen was passed. This,

together with the expansion excess from the furnace

tube escaped through the valve. After use,%nen

cooling was taking place, a somewhat more rapid stream

ergot; was employed at; it was necessary to have morn

then sufficient to conpensate for the contraction In

volume of the gem in the furnace tube.

The bead of the thermocouple was enclosed in a

May sheath which was positioned in the centre of the

material. It was felt that it was essential that the

whole of the arrangement, including the crucible should

be smenable to zetting in position 'anile outside the

furnace, and that the relative vositions of the portions

should not be altered on introduction into the tube.

c fulfil this requireAent, the whole of the apparatus

inside the furnace tube was susoanded from the top

bung. two stout nichrome wires were pushed through

pin-holes in the top bung, and these fitted sufficiently

ti htl ► to aaintslz an airtight aystem. Aarther,

force much greater than the weight of crucible and 0Opper

-41

?far found to be necessary to giove the wires.

aPeciel device as thervfore deeded to ia'event

movement of these wires when oarrjiug the weight,

uooks on the lower ends of these wires engaged with

hooks on a hichrome sling which held the firecley

crucible. This latter dies placed in i)osition, as

also was the themocouple and sheath, aud the surr-

ouu41116 copper. At the point at which the spioein'

seal was to be made to support the couple, sod to

seal its entri into the furnace tube, the insulating

beads were re:Loved 14v4. the wires, au the seal 4tade,

care being taken to keep the wires apart. The bung

and its attachments were then placed in position, and

one of the niabrowe animortess earthed. was

todnd to be neseasar, as there was a alight 'leek-thrum

frog the heating rods. .f tear replacing the air by

nitrogen as described above, the copper was tehen to

115°C., and bold there For half au hour.

t oc713.r a s tiled tclicweu to occur by riwuf.liw the

cur'“Jilt oarrie(.1 by the heatia rode.. ;Qadinga or the

galvanometer were taken every quarter of e ruicauta

Ourir*cooiiva,, the rate of which was between

and °O. per hear. it was not felt that much was

to be gained from the use of a mechanical recorder es most of these only plot at quarter einute intervals.

eo very obvious halt was noticed in the coolie e, and

when it was cold, the crucible was removed from the

furnace, end the contents examined. Meru were

absolutely no evidence of oxidation of the copper,

but it WD2 found that the thermocouple and sheath had

Floated up to the ourface of the copper while the

latter was molten.

To overcome this a plug of alundum cement was

mede to fit io the bottom of the fireclay crucible, end

in this, F. pocket made to take the head of the thermo-

couple eheath. his, it wee thought would meintein in

a horizontal plane the base of the sheath. To prevent

any rise, and to fix the top of the sheath, a lid was

aade for the crucible, and the thereocouple and beads

es.eed througev this. weight of the lid was

arranged to fall on the sheath, noel n rim on the lid

contacted the top of the cracible, and 'eept the former

in position. Ath this arrangement it was neeeesery

o eaaure that the head of the ti ere000u le wee

laced at a suitable dietenoe from the bottom of the

sheath ss the latter would be in poceet of elundue,

and not in the centre of the oop,:er mass. Vials set up

in shown in figy,...*

About S. $. of copper ()ere melted in a crucir;le

incorporatiniq these im,;roveaente, sag oboling allowed

to occur as before. :here was a halt of satisfactory

di .melons in the cooling* and this lead to the

atandariss ion of this arrangement for work in ea

open crucible.

(ii) he cloned tune arrangement. ryvax glees tub

of plain design were first usee. :&bout 35K. or n copper-selenium mixture of 99ets, oelenium was

prekared ano placed in such a tube* and the latter

evacuated and sealed oli in the manner, described above

(nee Emotion 3.). platinum-platinum/rhodium thermo—

coeple Nvas 01acvl aloa$!; the outside of the tube so thet

tae ,!unction was about an inch and.A half from the

rounded end. fhis position 7/86 adopted as it was

expected that when molten* the alloy would occupy about

thrbe to four inches length of the tube, and thus the

couiae head would have roughly au equal amount of

materiel above and below it. :he couple was attached

to the tube by a wash of 1-urinschoot cement in the

manner recomaiended by ,an ri J. ales. 'oc 1922 121*

2272; 1923421,214. iuring the sealin of the tube*

the solid glass formed was bent so 2 2 to tem a ring

in a vertical plane. A length of copier "ire passing

through this ring, end through a bole in the top bung

of the furnace tube was secured above, and served to

suspend the alloy-containing tube. ihe thermocouple

emerKed through a hole in the bottom furnace tube

bang, and was connected a described above to a

millivoltmeter.

mile tube wee heated to 25 C., kept at that

to verature for an hour, and then allowed to cool

by switching off the current. ;:emperature readinF,a

eere te4en every quarter of a minute until 150°C.

was reaciled. A temperature-time graph was plotted,

end faileC to show any irregularity to indicate at

*hien point soliuification hau occurred.

This arrangement of tube end theruocouple iz

open to the obvious objection that the latter it

situated far from the centre of toe cooks meet,

and is consequently affected by factors other than

the teuperature of the material. ;1,zi an attelapt

to ilbprove upon this arrangement, en indentation to

take the there ocouple head was aede in the base of a

sealed tyree tube. indentation 482 oo14, about

a quarter of au inch deep, but did seeel to go note

way is igproving she onsition of the coule. lmut

g. of the mixture wieWsealeu in a tube of this shape,

waited, atla s6aih allowed to cool. ,gain no irregular.-

it/ was ;lotioeable in the teaperature-tiaie graph.

re oojeotion raised to the original method was felt

to zle still valid, tit to a reduced degree.

in au effort further to improve the position of

the ttlerm000uple, a further adaptation was Glade in the

design of tubes. ibis consisted in sealing through the

bottota of the ahoy-containing tube a nano* glass tube

iith a closed uper eat!, and of such to bore that the

themocouple wires in their insulating beads Just

fitted inside. ;',bout so inch of this tube projected

into the alloy containing tube, and about two inches

*ere left outside. loth this orrangewent, and that

eh it superceded are shown in fig. a. In this

nem orrangewent the thermocouple heed could be placed

in the middle of the moils of szaterial. further test

seleniuw. showed no sign i4t a halt on cooling.

It was found difilcult tb conceive that this could be

ode W 614 fault in the thernocouple position, boa the

only obvious cause seemed to be that the selsni u411 WR9

forming a glass. ,hile this type of behaviour 113 well

FIRS 7 f)'PE

71"PE. SUBSEQUENTLY

US ED

PE,5 of ro

4nown in respect of pure selenium, it has been shown

,ethewson Amer. Jhetas oc 19,7024067.) that

as little as of sodivai issafficient to break the

glass for cation, and to cause selenium to exhibit a

norms' freezing point, and it was thought probable

that ten times this amount of copper could have been

sufficient to ensure a similar effect.

ascertain whether this was in fact the cue

of the non-a;vearance of any irregularity in the

cooling carve, a 2Aittomic percent copper mixture was

prepared and uaed. This was ,laced in n tune of the

last (exit described above, and eet u in the Nboye

manner. he furnace and contents ,xere raiseu to a

temperature of about 4&:,°4 ., retained at that

temperature for au hour, nod ellowea to cool. hfilt

in the cooling ,ios observed at 377°' but none et

217°:;., the freezinr4 point of selenimu 6114.3eu

that, $13 heu been expected, the tube type and tewoeratute

aeasaring aystem were s6tiafactory, and that 1.e cause

of the lack of freazing point for the 99at. selenium

mixture was in fact the vitreous behaviour of selenima.

Ally one 6inor modification 4,86 made to this

errani4,;ient auxin the course of use. Jas =Isis ed

merely in lengthening the tube which serves Ks then ocouple

sheath so that it rested on a ledge formed in a

somemhat wider tube by joinini< it to as narrow tube,

end flattening the join. ;his narrower tube passed

through the bottom bung of the furnace tube, and

through it passed the thermocouple.

The advantages of this sAtem are twofold.

o-iretly the weight of the material is no longer carried

by the Klaus riag carrying this susoension wire, which

now serves merely to keep, the alloy-containing tube

in a vertical position and centrally placed with regard

to the furnace tube walls. econdly the thermocouple

is nom rotected from selenium attack for the whole of

tts length inside the furnace tube in the event of any

fracture of the containing tube during heating.

2onsidereole use of tubes of this type * uld

T:osciole in the study of the seleniule-rich ends

of .any metal-selenium or metal-sulphur systems,

especially if silica were used Instead of Glass.

(iii) ipparatus for use with compositions spproximsting

to pure selenium. In view of the vitreous nature of

selenium it is not surprising that no freszinfs point

can be obtained by the usual methods. f-or inclusion

in the phase diagram, the melting point as deduced

from a heating, curve has been used. "him Beene to

be , general practice for metal-seleniva -yeteks.

Unger Uhem. 19 2,12 133.) coated e

thermometer butb with amorphous celeniom, crystallised

this by heating et 15-004. for a period, end then

raise4 the tenerature of the thermometer in an

oir-jaoket, vud read the melting joint of solenival by

viaual observation on Ow bulb.

ccerting the fact or the dOrltrintsation of selenium

by prolonEed heating at 156°C•ip en opperstus to give

heetinR, curves has been constructed. in this, the

alloy is devitrified by heating in the same sealed,

evaeuated tube in which it has been prepAxeds And is

afterwards heated in nitrogen to prevent oxidation.

This apperatus consisted simply of a i n tube

of about 2,,:i.ems. length and 1.5cm. diameter weeled with

a test-tube end et the bottom. o this Tgere attached

two narrow sidearma, at distances of about two centimetres

from the two ends. he material whose melting point it

(;esiTfrd to find was placed in the bottom of the

ein tube below the lower sidear, end a GooO.

thermometer carried in the rubber bung closing the top

of the main tube -)lticed in position so that its bulb

was centrally placed with regard to the mass of the

materiel. iiry oxygen free nitrogen ►aa passed in

through the upper sidearm, an escaped through

sulphuric acid bubbler attached to the lower sideam.

after a period of at least two hours, it was considered

that all the air had been expelled from the tube, and

the rate of the stream reduced. ,f paraffin bath wee

placed round the tube, and slowly heated.

Alien a temperature of about 21,1) . had been

reached, readings of the thermometer were taken every

minute with a lens, and thus a heatin;Y carve could be

plotted.

1,1122glatilLARIRerature measuq116 2a4lErhent*

(1) 'thermocouple. The calibration woe deeigned to

test tne accuracy of the couple itself, anu to deteruaine

the accuracy and responsivenews of the whole set-up as

used for thermal analysis. ihus points below 62 G•

were obtained by melting standard eubetances in the

type of sealed glass tube described ebove, and a coolin

curve obtained using the set-up previously described;

for higher temperatures, a point was ootaineU using a

standard materiel in en open crucible.

ftree low temperature ataudards were use lead,

rm. ana the aluminiuw-copper eutectic. he lead

end larie were of '4,naler' purity of 99,98x, end 99.99

respectively, end were in the for: of sticks. ,'haste

sticks were of uuitable length for direct use in the

seele(i tubes. :hese latter were dvirin oawn with the

sticks iz positions and then evacuated :11a sealed.

tie aluminium-copper eutectic melting point was taken

on drillings from a sample containing the two elermenta

in a 2:1. weight ratio. ihis matteriel had been prepared

from electrolytic copper and aluwinium of greater than

99,99 warity by Aelting under a flux in a carbon-lined

salami nder crucitae, the whole being stirred with a

vyaphite rod.

she following were the results obtained:-

R. lead 3260c.

x. zinc 420°:).

copper-aluaiinium eutectic

nese cowers xith the oeet figures available as followst-

lead 327.3Qes

zinc 4190°C;.

copper-aluminium eutectic 543°k;.

the values for lead end zinc are those au secondary

standards on the international ;Imperatore cale

-51-

tandards J. lesearoh, 1923,1,635.). The value

tor the eutectic s that of -tockdale Inst. etals,

1933,21,111.).

in view of the high puritg of the copper available,

and the paucity of satisfactory standards in the

temperature ran 6e to I1Q6°Q., it was deciued

to use thia copper as itanuard. About &egg of drillings

were placed in a flreclaj crucible and set up in the

usual way. it wa3, anytbing, more necessary than

usual thet no oxy6en shoul6 be pre eat ;.12 tha tube, the

prtcess of evacuation and slow admission of nitrogen was

carriuu out a total of five times, and after the

attach eat or a sulphuric acid bubbler to the bottom

of the furnace tube, a slow streaz of nitrogen was

aelatnined for two dela. The bubbler fulfilled the

function of preventing any back-diffusion of eir into

the tube. AS the nitrogen had been pasqed over tho

heatud col er 0,auze, it was felt reasonable to assume

that Lae percentage of oxjgen In the tube would be so

low E.a, to be negligible. raiz view Wba coo= out spy the

.1,ope of the cooling curve subsequently obtained. The

6.i/stem copperi-ouprous oxide possesses a eutectic at

t. of oxygen, and at a temperature 2,2v. below

the freezing point of pure copper. Oonsequenti/s if

any point on the pure copper—eutectic curve represents

the commencement of solidification, then a very slight

change in composition of the liquid will produce a

comparatively large change in freezing point, and thus

there will be no halt in the cooling, but only a very

slight pause. The curve obtained showed a very

substantial halt. Rather this can be seen, by the

character of the surface, not to be due to the eutectic,

as this latter has a dull surface.

rho value obtained for the freezing point of

copper was 1077°C. hta compares with the standard

value of 1483°0. recommended as a secondary fixed point

on the international eemperature.:crate (:Air. Itandards, J.

hesearoh, 1928,1,0,0.

All the calibration values obtained were plotted

on a graph showing the relationship between the

apparent temperature and the real; in all eabsequent

cases, real temperatures were obtained from the apparent

by reference to this graph. in this way correction was

mode for the couple, the millivoitmeter, and any factors,

such as the thickness of the thermocouple sheaths,

inherent in the apparatus used.

(ii) thermometer. The thermometer used for the work on

pure selenium and very low copper contents was calibrated

in the apparatus in which it yate used. two fixed

points were used, the boiling point of water under

atmospheric pressure, and the melting joint of lead.

.`or the first beterminetion, about three

millilitres of distilled water were 0.:_sed in the

tube described above, anti the thermoneter so errened

that its bulb was about two centimetres above the

surface ca the watez. :be whole ma then heated in

a paraffin bath, and tie water boile(. ;he temperature

reached by the thermoileter, the bulb cat which wg in

the steam, was noted, together with the atmospheric

preesure. The results obtained ware:-

.bserved boiling point of water

99.9

Atmobphere pressure

7t57 12m.

ie.hperature et Nhich water lin$

vapour prey sure o Maim. 1 i.J.26°

orrectioa to be applied

The standard value quoted for the Temperature at which

'nater hne a vapour pressure of 767mm. is calculated

froia the data of Walborn and genning (an. saktys•(iv

19A2S,8330#

In the case of the calibration with lead, difficul

was experienced in keeping the thermometer centrally

placed with regard to the pieces of lead stick used,

these latter tending to push the thermometer out of

position. This was overcome by premeltiag the

lead 'in situ' in the ueuei current of nitrogen,

but substitotine for the thermometer a sealed glass

tube of very slightly larger, external bore. hen

the lead was zolten, this tube weu eositioned

centrally, and the whole allowee to cool, mhen the

'sea solidified. ehe glass tube woe oroken away fray

the lead she cold, and the thermometer inserted in the

hole left. ey this means the therwometer was ceetrally

placed both before and during melting.

2ne apparent melting point of lead was found to

be 3247.1.° nO quoted above, the true melting point of

lead ix 327.3°C.

ehe relationship between tte reel and the apparent

teepereturee et erase two pointe was plotted, end

oesueee to be linear. ;he correction to be applied

at 23 5°C., wound the melting point of a dlre selenim4,

was then found b interpolation, and was 4 ‘og

,sterisle used in therm?). analysis,

q)th the dipper ene the selenium used in the

preparation of the melts for, thermal anal:vie, end

indeed throughout the present work, were of the

highest purity obtainable. che veleviue was from

qohnson k;o., and wne ,,usranteen grenter

then 99.5,. pure. :he copper was frog - hon. :'Bolton

-td., deoxidit-Ad, and spectroscopic analysis ehowa

it to be purer than the so-celled 'spectroscopically

pure' copper, having a copper content t.ovater t n

99.994 assuming oxygen to be ebeent.

1314: .S& 4i!

Vz SIG78.1 "e—Cuk*4

( the low tem224,ture method for seleniva snu

of up to of copper.

AS stated above, thin method weatured melting

points as distinct from freezing points measured bj

the usual thermal analytical procedure.

or a determination on eleziental selenium, about

g• were placed in the tube, and after rapid passage

of nitrogeu for two hours to remove sir, heating of

the -.44reffin beta rc,.s com4encod. kt the size time the gan flow was reduced to a slow streaa. Alen the

temperature had reached 21 .ot,4, it was found that the

rate of heatiog ens Cetween 10 and 1.5°U. per Ai.rautw. ,feetinf:. weir continued at this rvte, ano every s minute

tine tewperature ns given by the thermometer was read

4ith the assistance of a lens. :%rom the figures

obtained, the slower rate of heatiair, .Aurirq, e1tirt4,

of the selenium was quite evident, end on olottinA

tomi,erature against time, the same shape curve et, for

a nor .e1 eoo1in4 curve was ob atm. melting

oint Icas tern as the lowest temperature at Nnich the

slower rate of beating was effective.

it wee of interest to compare the lumerical Cata

57-

with visual observations on the seleniuca. it was

found that a slower rate of heating was effective

at a lower temperature than that at whit= melting

eou/d be seem, ;lid that before all the selenium

appeared to have melted, a more rapid temperature rise

was again in onemationm thus it e; .ea' that the

visual efgects have a time lag ac compared with the

actual melting phenomena.

In the oaae of olloys, these ;punt be prepared

beforehand, and *ot 'in situ' as in the case of

freezing point determinations whin the reaction may

proceed in the livid state icAmediately preceding

cooling. :,;apples of L•51, o.25, and ().1 of copper

were prepared by heating 5g. quantities of aixturea

of these proportions in sealed, evacuated glass

tubes for 12 hours at 25A;. On cooling, the

selenium in the alloys wan in its usual vitreous

form. 1evitrification was effected bq heating at

1N°C. for throe days.

The tubes, when cold, were opened and the contents

crushed in an agate mortar, and then placed in the tube

of the treltinc point apparatus. 'lie removal of air,

end subsequent heating and deteraination of the melting

point wars carried out as before.

rho renalts were as folioss.

comosition u.54 w. F, Cu W Cu

7Jbserved melting point 215.3 215.3 215.4 215.8

*orysotion

*ectual melting point C. 216.2 J16.2 216.3 216.7

it was found to be somewhat difficult to form any

conception of the probable accuracy of this method. in

an effort to obtain such information, it was decided that

the calibration for lead should be repeated several times.

Ms values obtained sere 326.100., 326.2%4., 32G.2°C.,

326.3°0., and 326.2°C. ?ram these figures, the mean

value of 52a.2-,i.eo was obtained for the melting point

of lead, and it was in fact this mean value that was

used for thermometer calibration. Thus the probable

magnitude or theecrore from all sources would appear to

se covered by' -a.1o C.

A.th this in mind it is seen that the difference

between the values for the melting point of selenium,

and for the alloys of low copper content is or

significance.::'rum this it toiloss that there exists

a eutectic in the low copper content region, and that

the system is not of the monotectic variety. rurther

-59-

it would tees that the eutectic cowposition is leas

that t.Vt cot per az in none of the aLloys examined was

any beating halt observed between the melting point of

the eutectic, and that of pure selenium, as would be

the case if the tatectia comtosition were to the

copper rich aide of the alloys exataineb.

tearing in :wind the tounting inaccuracies which

:would be encountered in preparing alloys of less than

o:ipelt, and *JW that fax the rest of the system

.1; re;.,resents the et,Imposition accuracy attained, it

wise felt that DO useful purpose would be served in

attempting to locate more accurately the eutectic

cotvo)iLion.

halt in tuolins had been obtained et 3770 for

an ail1oy tf co4osition 2, at. copi,er see, section 4.).

There tun, however, evinence which sugyested that not

the whole of the 2 sample bad welted. surface of

the .311 after haatind 4aU not atenoth, and the ul.der

portion of the StAZi, 4u$ not in contact 4ith the walls

of the tab* as wnz the lo. er 2, mixture was o, again tretpared, anc heattt tt t.,tught to be

the highest temperature safely attainable in ,yrex

Lless, a.ainteined zt that tampersture for an hour,

and cooled. in additicnal halt WAS noted at 523

It was desired to bald from this by taking

coakesitione on either side of 2 and gradually

extondinb the composition range. ,-ith this in view,

a nauplo coptaining 15 at. oopirer wac prepared, and

heated to 62%,°;;., at which teapersture it was maintained

for about au hour. ,00ling wee effected by lowerins the

voltage supply. vi re cooling curve obtained showed too

:cults, uue at 525 ,.;., and the other at 373°0. t

capper alio' again showed similar reaults (see table),

with no other irrtigularitj in the mte of cooling such

as sight be attributable to heat changea in the material.

%Antinuins the extension from copper towards

pure salaam., an alloy of 7,5: coilper was thermally

anal/sad. he cooling curie aLimin showed a halt at

373°., but the duration of that at 525°C. had become

so short that it was represented by two readings at

2(..°,;., with a ,suarter of a Ainute only between them.

the rate of cooling at this Juncture was only 25 ©/hour,

it was considered possible that this 2suse was of no

signifiaance. Alloys of 6 and 5 at. copper both

showed a halt at 577°1., but no other significant

-1—

teatare. a he 41 alio', on cool in from 6,,

showed no irregularity at all es tbe duration of

the 372°'. halt, previoas4 dacpaasing with lower coppttr content, had nom become so short as to be

undetectable.

4teusion toosrds higher copper content of the

composition range studied shooed a continuation of

the halts at 523°C. and 377°4.;". up to 47.5 , copper,

which. was the tiost copper—rich allol examined at thin

;Mace. Nva figures obtained are shown in tau table

ovvrleaf.

an the caae of upper, the 378° halt'

showed 3°,./. suseorcooling, but this was not encountered

In ny other case. rho durations of the two halts did

abut behsvu ioentically, as that at 525Qk;. continued to

iucrease with the copper content, while that et 378°.

aJpeareu to reach a eteacy ouration oz auout six

winu4os for about 4vg. of silos at about 35at,. copper,

3ano increase of 014. ,er content above this fit urs seemed

to ,zouce e sowewhat shorter period of halt.

L.onnikAeration of :he results prefaente6 in the

table showed that the t aints obtainao forated tgo

straight lines parallel to the coAposition axis of the

cop or ialt tea4)eratures Q.

t,

5

5.7 be +)

373

377

379

7.5 378 52o(?)

Lie 375 524

i5.v 378 525 24.v 377 525 27.5 377 523 32.5 378 522

37.5 377 523 W.6,1 377 524

45.Q 377 522

47.5 377 524

equilibrium clagraz. In general it is omissible for

tqe li uidus curve to be horizontal only when there is

a adscibiIity gap in the liquid state. :ince there

wc,e1 no evidence of incomplete melting in any of the

alloys studied, it seea4ed prooable that the upper of

these two straight lines Nas, in fact, the licluidus,

-63-

aul therefor the po'isibllity of the existe400 Or

too /14oid lagers :dad to 'ae oozu.iuerod. Visual

oxalination of the alloys prepared failed to suet

any line of demarcation.

A) deter:line whether any such alsabillty

existed, &Nutt 14. of each Qt 14, 2.4, 3,), a* *ALIO copper mixtures were preiesred. rhos* vantities were

aealed la evenuated jurva glass tubes of oplAtin,

rouadvbottomed design. rne tubes were suspended in

a vertical position in a muffle furnace, and hea;ed

to about 4* 'Ater being maintained at this

temperature for 24 hours, the tubes wore venohed by

withdrawing into the sir, when they became cool enough

to handle in about one slants," The tub a wore broken

open in sash a manner that the ingots were retaineu

in one piece. Ilings frem the ;op and bol:tou of each

ingot tvere placed, atter .,:rinding, in .,indetAano glass

capillaries, and nubjected to X--ray di 'fraction in a

9-ca camera. Aitt rus obtained were interpreted

in the light of the standard patterns already avail t e. results era given in the table overleaf.

ince these were results frot, luenched s ecienes

the Ji-fference in constitution betNeen the tcq, end

bottol of each ingot could not be due to seR;regation

havini; occurred on cooling. ihus the miscibilitx

i,ar extends over the rang4e co.iTert and einoe

in oo h the extrea.e onsea exasinec there was a

tAfference in coN,osition oetweea tale two lagers

Coalipo0Aon of luot top or bottom inter-retation

1.44 cojypex tor, no lines

bottom -e

24), copper top no lines

botto%

3t% copper

top no lines

',Ott=

copper top t;u1,a, but faint

oottota awe, strong

these figures do not rooresent the limits of immiscib-

ility. The lower of the two layers was substantially

al 'e, end it was assumed that the absence or lines on

the ttorn of the upper layer indicseu that this was

selenium present in the vitreous state. The difference

in the constitution of the two layers was Destiny

apparent on examining the fracture of each. :bat of

the supposedly selenium lager xas typically conchoidel.

while the aelenide showeu a crystalline fracture.

0 2 -Y- 10 IL 1 xf- 1 6 le 20 zs- ".4, ;46 zi JO .)X J.*

TIME (NliNv -rE 5)

(iii) To determize the extent of the two liquid region

o noes a quantitative determination of the

oompositiona of the two lieuids, about L. of each

of eix mixturee were prepared. or the determination

on the eeleniumerich layer* 7.5, le, d 15 ate copper

were eeployed* end for the selenide layer 35* 4e, end

eeate Thece mixteres were pieced in :yree g1 s:

tubes* end the letter evacuated fled oeeled off. ehe

tubes were supported in a vertical position in u chair

of thick niehrome wire in n auffle furnace* and the

temperature raised to 54-e-5500•0 and weintained thus

for fie days. The temperature was chosen so as to

be above 525oi. * the melting point of the eelenide

layer* but to be as neer as eoseible to this, as it

war conoidered thet a comearatively emell ineresee

of temperature mieht decreaze the olecibility gap to

an appreciable extent* end thue &lenge the compositionn

of the two layers. Vitae time of hemtine was increased

over that employed in the cane of Xerayed specimens in

an attempt to iteeare aomething approachins quantitative

GO aration of the lnyere.

en quenching the tubea in carboa tetrachloride*

and carefUlle opening, it was sees that 6he lower

1.1 1.2

98.6

1.4

1.2 1.1

1.4

layer - the seleuide layer- haO become, ooated with

the wgper 'opal) due presumably to the forwer

solidifying, an( watreotinK aut4- grout the of

the tube before the seleuium Klass beutwae sufficientl

viscous topreven flow. ilaluo 4Orki ;,s .en from

the sAlenium-rloh Oapper layer of the three mixtureu

of lower copper corteat, aud from the lower layers

of the miztareo hig,her copper content, care being

taken to svoi4, or remove, y portions of the in

h1 ,t ere obvioutIly contaminat the other

"4- tie r,:::.6ults obtained are shoo ,:.3 followo. 7.5h upper layers 1k.,4 upper layers

or sample takon Q.2455g.Q.1863g. o.2613g.u.283601.

of selenium

raged ,J,2423g.u.1844. t..2572g.u.2798g*

J1 t. selenium 98.7 98.8 98.4 98.7 vol. of Q.1,;31.:4

thiosulphate for ba.47m1. u.4 1.

eolTer titration

tat of copper

el. „7 selenium

0 eOpper

of sample taken 15 upper is pir 3 lower layer

w.3007g. v.3291g.iJ.3262g.

. of selenium

recovered

colealum

Vol. of 1)31e;

thiosulphate nor

coi".zer titration

t, 4 copper

.,o1 seleniurA

Me. A copper

15, upper layer 35.,, lower layer

.,.2553g. 2959g. .19191. .151Li2g.

93.4 98.4 5a.3 5e.3

19.0m1.19

37.94 38.25

55.2 44.8

4kev lower layer 45,., looker layer 4t. of nample taken u.2337g..-.39628. 42236g.u.2349g•

it:. of selenium

recovered ,.1337g..;. 2292g. J.1278g. .1338g. 53,1 57.9 • eelesiuls 57.2 57,Q

.01. of ,.1u31d

bhionulpimte 14.72m1 24.99ml. 14.69‘1.15.53,1.

• copper 41.,T 41.3 43.1 43.3

aelesiom 5,3.j 51.5

copper 4 464.5

In view of the comtamination mentioned above, it

kieemeu desireable to take values not the mess of taose

given, Gut rather the extremes — i.e. tue poorest la

copper for the selenius Tina layer, sou the Tinniest in

(sapper for the selenide layer.

The possibility wna considered of plotting

these resulto as a function of the original composition

of the alloy. end extrapolating until the composition

of the layer was the same as that of the alloy. This

would represent the preaenoe of just one layer. It

waa considered that while this procedure night be of

nee in some cases, in 4eneral the contamination was of

such a random nature that no useful purpose would be

oer7044.

in this region thermal analysis was carried out

on alloys of compositions 48.6, 49.2, and atomic Ai

a copper, and while the restate are summarised in the table, they call for a sumo/diet-more detailed discussion.

The alloy 43.6: copper shoved m sharp and definite

deoreasts in the rate of coolin at 52941.... phis

reduced the rate of cooling by a third to a half, but

was not a holt as cooling continued. The same halts

30 before Isere noted et 521

and 377°Q. for all three alloys. The 49.2A alloy showed an effect similar

to that described at 529°G. for the 48.4;. alloy, but

the temperature was 547°':. 'ihere was also an saditional

halt at 529°O. This halt was again shown bar the

5Li. of alloy, and was distinct from the 522°C. halt.

The slower cooling representing the commencement of

solidification was evident at 533°G. fox' the 54.0%

allo7.

Aomic & copper

lnitisl solidification

aalt I halt 2 Halt 3

48.6 529 522 37?

49.2 54? 529 522 377

593 529 523 37?

These results have been interpreted as follows.

faros 523°0. and 44.% copper, the liquidus curve rises

through 529P0. and 48.6A, 547°C. and 49.24, end 593°

end copper. The halt at 529°0, is considered as

being due to periteotie formation of i.;alse from Cu -rie

and a ltavid of composition 49.2t, copper. Thus on

cooling a melt of 5Q.0 copper from6,0430., at 583%.

separation of Cu2s4 commenoes. — end continues until

the temperature has fallen to 529°C. when the

composition of the liquid is 49.2-4 copper, Kit this

temperature the Ca 2 e reacts with the liquid to give

Cuie. 'las, like no many- periteotio reactions, does

not proceed to completion, but some unrescted liquid

remains. This deposits Cul-Pe es it cools until it

et,cheu u., 'Olen it huu cowkositio14

copper. A: this to +;r+ asparatea until

the cuiapositiou of tie romninin - is 1.k:

c(41,:er. 0011.11L tilea restbitb, EL21 0.ot:teed's to

7/1° allotle:v halt occurs.

(vak 'hs significance of the beIt_st)a V.

in visa of the fact that vu2o3 is prepayable tit

.jv 1.4, and not at '4J U. as was shown in section 3, it

team thought possible that the halt at 3n t, might be

due to peritectio formation of this from ;ArAt end

liquid. o teat this sugeution, a sample of

copper was heated et 2-5 *j • for six hours in a sealed,

evacuated lyrex glass tube. un cooling and subjectiag

to k-ray diffraction, the pattern of Qu2 e3 was obtained.

Two portions of this material were sealed in tubes, and

heated, one at and the other at 42oQQ. for two

days each. :,;42 cooling, and subjecting a sample to

x-rey diffraction, only the lines of QuAt were found

on the sample heated to 42u"Q., while the other was

unchanged.

Hupport.for the existence of Cu2 e3 below 377°0.

was also obtained from observations on the effect of

tipping at about 32j3C. tubes containing alloys

nad /4Y'.“ copper, idle the for.ter sho4e1 :.)resenos

of ll'uid phase, the latter did not.

the stem ;A0-QuAi and deal. ations of two- luso

11 the data listed above ere embodied in

which shows the equilibria relations for this syateta.

Abe re ..oh in doubt were tnose designateQ

Se+OU61,39 and Que4.4112003. ro cover these, alio sa

of 2 and 45', copper were prepared by beatinE an

25°:. for 2Q hours. The alloy was then bet,

for four cloys at 13')C1, ian an effort to devitrify any

selenium present. -ray diffraction patt;eras wexe then

taken on a 9 u* camera. he enteblishe(1 method of

comparing .--ray diffraction patterns iz by intensity

and '0' values. 'ale measurement of ray filr4s, sad

the cYlculatios of the :sragg angle la des cribuo in

section 0. Kon the :.tragg equation a io

seen that the value of-4 for any given line is

dependant on the value of),, that is on the wave

length of tae r,-rays employed. Arne, for comparison

porpokies it ia undesirable that values of should be

used, and 'di values are in fact employed as these

are independent of the ray wavelenIth, and are

LIQUIDS

Sc 5-00

THE SYS TEM Sc.--Cu5e.

boo

Cu Se Lt

4o0

m

-11 TT)

m

Cu 5€ -t-

Cuz Se3

2 00

Cu, .5e, + L14.

Cue Sea

too

So

Cu5e

4-0 30 COMP 05i TION 20 10 Se A-17-% Cu. cu2 Se3 FI4 4

-72-

measures of the actual spacing within the er7stel

Vrom the patterns obtained, '41' values were

found, and compared with those from standard patteraa

of the phases expected. An example of such a

comparison is shown, and demonstrates the correctness

of the designations made.

2cs't, alloy selenium s tdt Pds I 'd'

2Ogy alloy 1 soi,

selenium I NI'

Cu. be 3 I 'de

4 3.73 5 347 10 2.97 11.) 2.99 fit 3. Oct

3 3.20 23.34 5 2.87

3 3.18 4 2.63 8. 240

5 1.50 3 1.30

4 2.6o 8 2.63 2. 1.45 1 1.43

3 2.38 4 1.42 3 1.42

1 2.3 I 1•37 1 1.37

2 2.16 4 2.18 3 2'15 3 1.31 2 1.31 2 1.31

4 24606 6 2.(1/ 4 1.22 1 1.22 2 1.22

5 1.99 5 1.99 2 1.17 2 1•27 1 1017

5 1.96 10 1.97 2 1.11 1 1.12 1 loll

3 1.90 2 1.91 3 1.08 4 1.09

4 1.86 41.87 3 1.o7 2 1 3 1.t

3 1.82 2 1.01 1 1.01

4 1.80 3 1.81 1 0.97 1 0496 1 0.97

5 1.76 5 1.77 4 1.73 1 0.90 1 u.90

2.4-; alloy selenium c.Yu2 e3 2i...7; alloy selenium Ca2oe 7 di I .i. i s u .1. 'd' 'cif 1 'AP 1 'd'

1.69 5 1.70 1 x.86 1 i.).38 1 w.813

i.i:)4 4 1.65 1 w,85 L x.'.85

5 1. i>1 4 1.63 3 1.62 1 ,J,84 1 c,48t+

1.52 3 1.51 6 1.53

siOTtOri VI

3Y8TEW Ca-Cu2se

. no tuis,atatik At Cu e

i) Introduction

Allis portion of the eol,par aeleniuu. system tlad

been 4,retriouell studied to a certain extent. !'he

lividus and soil( us carves were plottec: by friedrieh

and fArotur (see introduction) as a result of thermal

analysis. A certain amount of 'vork dad also been

done on i;a2 ;a concerning eapeoial ly its structures nd

transi ion.

Me wort of ;°riedrich and eroux was however not

of complete nature, there being such detail on the

ligaidas curve which these workers oiere unable to fill

in. in view of this, it was felt that a complete

redetermination of the solid — 1i laid equilibria might

be mane.

'.Joncrning the structural cork already carried

out on s u2i e, in the L:.aia it was decided that efforts

;mould be made to extend this study, end that repetition

should only be effected in so far as it was necessary

to correlate any new data. with those already availaole.

(il The kiscailltZESLULI11115Eititem one of the feetaras of the system PS found by

A‘iedrich and r.eroux, true a miscibility gap of which

the ext ut wa:t not accurately det9rmin:sa* but -:hich

frpeared to e7int from about i3.. cc;per nearly dOwn

to 'la.

aloys cant nine 75. 8J and 35, cop; r 'sera

prepared. "fie method c,f preparation differed from

that cLq=lo.xed in the plate:a ,e-et we in that the

nelenicm was not ad6ed au eruct., but in the for of

the equivalent cmount of Qu.re. This wali considered

1.referable rocodure nn Ou aQ waa thou6ht to be

re/ativell thernostable* while selenium al.j ht volatilise

quite conside7rb.4 even at tec.perc,ture:3 beim that at

which cottbinp)tion with copper would occur. /. (uantity

of the ieienide wam prepared by heating about 2,ig.

efuouLits of a mixture of the relative 4-,ro;ortions in

set led kyrex tutee at 25u°1,i.

'or the suovoqueut thermal $3nalynim the oven

crucible technique describe in section 4 4an used.

he crucible wee veigheb together rith ita base plus*

the thermocouple Olean which Fitt .'d into the for;,eri

and the lid. quantity of copper was then placed in

positi 4 on the Usse plug around the sh, th* and the

whole re. eighed. _he quantity of selenide needed to

the ..3 seleniva content in mans i.bout 4r,g.

Wa4 then 4olghed into the crucible, and this woe

sollo ec ay as nearly as i?0341141. cori(ict amount

Qi cooper. fu this wki the selehihe ilea located

between two lajers of coi4ers and was in the most

advantageous position for diffusion through the whole.

bein rJaintaine at 115t4°Q. for an tours

the alloys were vAlowed t oocd low*riu- tae

voltao,e supply to the furnace. Le cooling curves

oA all tarea alloys when plotted showed two halts,

one at It42-68°44$ and the other at 1Q7 33°0. am

figures fur the individual alloys may be seen in the

table below, 1ie duration of the halts obtained

naturally varied with the cowpoaltion of the alloys

and other factors, out under tAe wo3t Xavorable

conditionas hats of up to ten minutes were obtained.

.to the cape of both the halte observed for the alloys

under, consideretions snd indeed throughout the r on

'Al les supercooling VISA observed. 'he e%teut tai

this 't /as normally small, usually laws than 5 but on

°caseloads supercooling of up to 8 who noted.

she alloys were allowed to cool in nitrogen, and

when cold were removed from the are-clay crucibles

13;1 the prodeas of breaking away toe letter*

found to be the only method of removing ingots or 10se

than 17.5- Co per. 'those of higher copper content did

_77..

not adhere to tha crucible, and could be littel out.

The thersocourvle sheath and bane nluT which

were embedded in the ingot 'lasses, were broken away

no completely ne posolble. 1-11e inopto were then

gown throuKh in n vertieml ',lane, end the presence of

two layers was quite obvicue from visual examin+ tion.

upper layer was black, end of cry: talline frioture,

and the lower wee of the general colour of cePper.

"tile alteration in the relative proportions of the two

layers with eomposition was noticeable in the rause

75.4151, copper.

A quantitative determination f the poeitions of

the endn of the miscibility cap was naee in the name

3enerel manner as for, the othor two-liquid region

(see lest section). About 5g. each of nixtures of 75, S', and copper were prepared, and placed in

silica tubes about 7 oa. long, and of u, cm. bore, sealed at one and. The tubes 'ere onretully evacuated

in the usual way, and senleC eta constriction about

Yea. from the seated end by means of an onv-noel gas

The three silica tubes 7ore arranged vertically

around a clay thermocouple sheath In en 'lumina tube

about nem. long, and ,em. bore, and closed at one

end. The silioa tubes sad the thermocouple sheath

were maintained in position relative to one another

by peeking the alumina tube pith sand. This tube

-;;13 then 'duns in a chair of nichrome sir., and

suspended vertically in a furnace where it man

heated to ll'X)-1130°C. for 3) hours. At the end

of this tile, quenching was effected by dropping the

sluaina tube into a bucket of water.

ua breaking open the silica tubes, it was found

that the degree of separation was not as high as hid

°eon hoped. here Appeared to baye been a surface

effect at the silica tube whioh had caused the upper

layer to coat the lower layer. it was noticeable in

the case of alloys prepared in fireolay craoibles

that the siniscue at the crucible surface was so

shaped that the eagle of contact of the lower layers

was obtuse.

loth the layers of the alloys obtained were

analysed, care being taken be avoid contaminated

portions, and also any portion which had cooled in

contact with the silica tube, and which sight have

aoquired portions split off the surface of the latter.

he only modification node in t analyti procedure warn that 1/5 and lau the total copper Was laid for the for and the 1 er layers

Alloi 7,4 Vie, lower wiper lower wt. of eller taken 1.W37fit I 07408• 1933158. t. of selenium

recovered `St. aal.faiea 3.2 dal. of 103.14

#tiaaalpe 15.8 'St • Wiper 96.6

• * copper 97.4 selenium 2.6

w402g. 364 3.0

19.62n1. 63.2 96.6 68.2 97.5 31.8 2.5

• 851. copper Wiper Ou lower upper

at. of alloy' taken kmeing 1.5415e. 1.0631g. of selentuw

recovered aelaa

dal. of 3V1

3.0 0.3?68g. 35.46

15.97a1. 22.79.1. 20.77*I. n. 4 per 64.3 96.9 64.1 may. sapper 69.2 96.9 69.2

% selenium 30.8 2.4 30.8

svespectivel24 40.6 el.reeted by M04-44;; the

solution coataihin the 4aole tf the copper up tic)

in 4 4roduated fines, anJ takinq; either 5:) or p,ortiane tor titration. .11e result at

presented In the above table.

i'eKiag extremes es bei4lre, i.e. considering

the composition of the lower iver that obtained with

It ;$ selenium, and of the upper layer us that obtained

with 25; selenium, the molecular compozations of the

two iayers touad to 04 and vV.6. copper.

Aherasi anUyalo in the rouge 1Qo...,95 copper

The standard open crucible techalque was used

over this range, the selenium wising *flood as -;e es

described above. Ilia results an deduced from cooling o curves are acrown in he acjiment tables . C

:401. copper Qommencement dutectic If age of of malt lisolbility

solidification gelP 1 ) 1.33

143 1068 99.5 It/L) 1068 99.0 106? 97.8 1074 1140 90., 1067 1v81 #,5.'i 1063 1:85 8034 1062 1(42 75.o 1(66 19

-81-

AS in the case of the sealed tube technique,

the commenceaent of solidification wee easy to detect.

ale efZect of solidification on the cooling curve was

greeter for the 99. and 98.5.;', alloys than for that of

composition 97.1,3 copper. Aais could be expected. es

the sloi,:e of the liquidua curve i greater in the

lattai. came than in the two for, er, and thus more

solid mast separate for a given temperature drop

the former cases than in the latter.

2rom the above fl ures it was seen that from the

welting point of pure cower, the liquidus ot rv.. falls

to a eutectic at 1J65°C. Frog this it rises again to

t0,e and of the miscioility gap at 2.V selenium and

1. 3°C. The exact composition of the eutectic has not

been detexmined. o separation of the ociwiencellent

of Eolidificatios bad the eutectic halt was posaible

for 93.ix-:) copper, and. iv extrapolation of the liquidus

curves of both aides of the eutectic until they meet

at IcAi6°U., the coaposition would appear to be between

96. and 98.1 atomic copper.

AS it was later found that alloys of higher

selenium content lost some of this by volatilisation,

ail alloys outside th misoibilit,y isap were analysed,

-941-

and in no case las any laza of seleolu4 found to have

oneored. to purpose could have been Jerved by

analysing alloys of oompoaitioas eithin the teo-liquid

rano as a variation wool occur only is the relative

orwortious of tne two laye a.

0.v) Mensal analy4M. Ottyleep_68 2 and 66.7. %wiper

only one alloy in this oamoosition range teas

studied. Fhis was 66.7 copper. %fter melting and

subsequent cooling, the ingot was resoved from tiro

cruciblo, tan the wells of the furnsce tube a coatin

of red zeienium was seen. The ingot was therefore

crushed and samples analysed. he crushing and

grinding were sufficiently long and thorough to ensure

that a sample obtained in this way was representative

of the whole. she composition of the alloy on analysis

was found to be 67.3/: copper, and it was to this

composition that the results obtained from the cooling

curve Neve oonsidered to spply. of cooroe, is

not strictly accurate as the composition of the alloy

the freezing point of whicn Ives determined arls3 probably

not eecactly that of the cold in: ot as volatilisation

losses may well have occurred Prone the solid material.

she proportion of selenium lost during cooling would

? 2 L IQUIDS tr

-Li IA .

- ..,

Ct., .. SG -t- i- i Q • 4-

A. X Cu -o-i-la

..

se ,...

Cut Cu e -5e

I ., . . . , ,

A- 070

4J

99

THE SYSTEM Cu,Se -Cu.

q/ 8 es Si 79 76 73 70 Vi 64 R.):;) -1-1 ,../N

Co

-83-

he expected to by very *mail as compared -Hitt% the

loss daring the hour that the alloj was molten.

ithe coolinq curve showed the coamencement of

solidification at 101%, and two halts, one at

1085°0. representing the solidification of the

selenium-rich liquid layer, and the other at IAA?

representing the eutectic temperature.

The diagram resulting from all these results

is shown in fiA. 5.

I . 3 Cu 4.;.3To.k ;1

(/ -fnermal analysis intnis range.

The only thermal analyses carried out in this

range aore at trot copper-rich end theroof, sa4

utiligea the open crucible technique. Two alloys

were ermined, and they both suffered considerable

ides of selenium or volatilisation, but the procedure

dose ribed In tree last section wan aJo-tod for the

determination of cosposition.

Jelenlum above tailt present in -,;;11 kAt was au ens

in the fors of Co.ne previously proatei:i by direct

=Jou of weighed quantities in twaled iirex glass

tubes. The alloys we.ze of initial atomic compositions

63.5 and 61.5 copper, and on analysis it was found

that :.110 final oihiposi'4ions nere cad 65,i, atomic

percent copper xes;oeetively ::h ,:t the :lore *

rich filloy lost a hilirhar ?ro ortidn of its 80 eniun.

e . usual melting ant; coolio!, ;,i.J4e..iite was adopted,

and both coolin oarveill shofiea r.:Ion$,, of slightly

retarded cooling. This Iss rif; 1,1dicatinp; the

cotmencement of flollilficaticn, A6 ccearred at lje0.

rind 1, respectively for the two alloys. The

retardation at 1,_;97

was more noticeable then that

et 1:460C., and this was taken as an indication

that the uldus curve had a /steeper slope at 1v46 C.

than at 1t97°.*

An attempt wrs made to analyse thermally an

alloy of 54.3 at copper by the open crucible technique.

In visx of the greatly inorsesed volatilisation to be

expected, the thamocouple was completely proteoted

by sealing the joins of the twin-bore insulating beads

with alunduxu cement. Ay the tilt* the silo had been

raised to a temperature 13at°0., to irest was tile

volatilisttion of eeleniuw, that this h d begun to

condense in tho tubo carrying nitro en into the furnace.

In view of this it was felt that no reliable determination

of the operfltive composition would be possible, and that

further beating AKht 4el1 lead to attack of the

thermochUple through crttee.s in the alundum joints

mentioned above. be effort wf4e thertfore abandoned.

orisiottration of tnee bases ezesent in this rahse

in the vralimilli)ry survey of tht system at 4%;";

Usee seetioa j the only phases encountered in this

rattle were .0u,se, t4,.:42, and k;u,,e. i. these,

Aaii not ootaihed irev isola GA4 ather4 a6 4 „J°Q.

Alloys of 54 and 58 at. copper suero heatiki

&',e, for 24 hours, end quenched hy' withdrawing

Ant* the air* 711 about a minute the tows were

suffioiently eool to handle. ray 7owder. )hotosraphs

wore taken of filinls from the to, rivi the base of

the ingots. Mese were tonni to show lines ()flu

lire, and a few of i;:u se. tiro lines were found

which could not be exrlainei as belonGin3 to one of

the known phases. Thuo the only irmularity. possible

an the liquidum curve between Cu and Cule would be

dat uo Cu3302.

sani4e of Cup)a prepared as described in [motion 3 by the method of loria, wns se:,Aled in R

.7rex , ass tube, and heated to 430°1. for two days,

and then •mulched in carbon tetraohloride and an X-refit

powder -hoto4raph taken. Virtually no lines of Ou31.2

were seen, but only those Of Cuile, with a few of the

stronser lines of Cilia, 'Thus it would eppeer that

Cu3 'le hoe a dedomposition point at a yeppsreture

belo-* 40Z.

This being so, Ca annOt ap esr on the

11,11.4us curve between rgliat and Coles for the *audition

of the sen?le heated to 4847,0C. showed clearly that no

melting bed taken ood that the decomposition

had occurred in the solid state. lt thus seems

that no irrernlarity mey be exrected en t:he licuidus

curve between Cu:'. end Cu4 e. ihe re %ate -lreae.y

obtained thew t falling curve from e

risies eurve at CW9. V.xtrapolation of thee* curves

ar already defined showed that they eaxe near to

meetinw, eo while aueb en extrapolation cannot be

considered to be quattitetively accurate over the

fairly large ranze involved, it does provide e

qoalitative indication of the phase rolationshipe

to be encountered in this region.

(iii tobility of Cu 2 The only preparation of this compound not

contaminated with other selenides area tat by forlais

method. This was analysed, and found to be componition

• ivt. selenium and 5u.1 copopr, 4vIng an

atomic ratio of 38.6 61.4. she sum of the weight

percent:, ges of copper and selenium pvia, however, only

in vie", of the wet DX000613 by which thls

material had been obteineu, end of the fact that its

only Oryins had been in a desiccator, it was thought

that r uch of the residual 1' would be water.

ci this ii.aterial was dried at

icor 44. dour. i5 it &i current of ultiolien to prevent

oxidation. iosiyals of the dried materiel showed

a composition 43.i at. selenium and 56.2 art. is

copper ivint, an atonic ratio of 5.6.5 61.5, and

a total gaight of 119.94,.

buls of the asterial was tnan similarly

Uried. ,stailtples of this :real aealed in evacuated

zyrox glass tunes aoout 4-ca, long, and wrapped in

several layers of copper foil and nested to pre-

deterAineu temperatures for considerable periods

after anion tney were quenched in carbon tetrachloride

and 3.-ray powder photographs teseu. flis copper foil

sorven to produce'eveo nesting, and prevented any

lorwation of a suollAata of aeleaida. the results

are :moan in tii Sjacent table.

4..p. of heating orration interpretation

4v °4 1G 41 vt 24ae Cu. (little

3J hrs. Cu3:A?2

less 1,tu

The interpretation of the films was made by

calculating /d, values and comparing these, and

intensities with the values for the individual

selenide patterns. The absence of Cuie, one of the

89-

suppoaed decomposition products, say be explained as follows. The composition of the initial material was 61.5g co, per. uwing to its non-stoiehionetrie range, the extent of whish WOO at the time unknown,

but which has been subsequently found to have a lower

limit at 613.Y. copper, the On2ile formed will have the

composition 63.5 copper. Aseuming* as seems probable

frau intensity values, that only about half the

Cu 0*2 had decomposed* then only about 8 - 91$ of

Ow* would be present, end thin. especially in view of

the nature of the materiel, a3.t ht well be insufficient

to appear on the X-ray pattern.

In an stuempt to secure come experimental support

for this hypothesis. further samples of Cuee2 were

heated as before in sealed glass tubes or longer

periods. usually a period of six days was allowed

to elapse before quenching into *Arbon tetraehloride.

Again the interpretation was by td' values. and is

shown in the accompanying table. Temp. of Nesting Duration 4.sterpretstion

250°0. 124 hrs. Ou2 Se Cue.

laec. 124 tars. Cup, OuSe

135°0. 120 hrs. Cue. 4. Ouse

128 O. 120 hrs. 0%13,802

Thus it wsa seen that Cu3ne. decomposes at a temperature between 12800. and 135 O. to give Cu 13. and Cur! . It vras not thought that any purpose would be served by attempting to locate sore close the deuosposition teperature.

The ed* values of the lines of the patterns hisated at 13500. and 128°0. are compared with the values for Cue C1,130 and Cu26e in the adjacent a.. 1230u. 5.940 4.269

7 3.555 8 3.561 3.342 3 3.359 8

6 3.203 7 3.24.4 7 2 3.091 5 3.109 5 2.863 4 2.868 4

2.677 2.683 3 2.558 3 2.562

2.363 2.373 5 2.254 6 2.260

4 2.127 4 2.137 6 2.47 5 2.21 10

350

3.56u 3 3.563 3.315 4 3.353

3.323

3.190 6 3.178

2.875 10 2.874

2.566 2.57?

2.1.96 2 2.199 2.175 2 2.151

2.026 lt j 2.030

-91-

1.992 2 1.996 1.962 4 1. 1.9143 6 1 9G5 1.821 7 1.826 1.823 1.770 9 1.775

3 1.720 1.631 2 1.637 2 1.624 1.548 1.55k;

1 2 1.431 1.432

7 7

1.357 1.339 2

6 1.201 3 1.203 1.184 1.163 2 1.163

3 37 2 La 2 1.104 1.103

5

5 7 10 9

3

2 2 2

lir) „utt-utoiciiio,Autry

bile there had been no systematic study ui the

range of non-stoichlometry of Qu .41', there existed

in the literature several observations that left

little doubt as tu the existence of such. a rata e.

.40121fis (4.01sik C,hem„ * 1'331.14151.) ntated that;

the .4-form of i:A* s could exist witA covper delac it.

goiahold and A'arihg. hem,,300)37,4Eta,q.)

stated that this rano extendeo to 614,5 copper, end

3orchert 44rist.,lti45,1 cs,54,) gave figures for tne

lattice parameter at various coz,positions.

in order to make a thorough study of the subject,

n number of

coaposition

of coi)puve

Aeatia4; the

tb„,ether la

eatine w

alloys were

.5, a3.5# ,ttout

prepsiad• these were of

66.'5* 0745* at*Gie

of eaca alloy:Tale prver3d Jai

rc •ifol tloants or cop:Jilr sad Lielehlua

evacuated, sealed _yrex aloes tuber;.

AN4 lasted for 16 hours, daring

ch tie the tu'oes stare wra; e in co;, er sheet to

give unifor aestirs. After havill cooled, each tube

was orArned, 4,..zu; the contents .rotlaci in an agate mortar

for about hall 80 hour• -Chia w co siaored to be

sufficient. to cause thorough akixing, sad to give a

40MO;Od0OUS ;?x duet.

AM14 1.5g. of eaen alloy xas sealed in en evacuated pyrex glass tube, 4rapped in sapper foil,

and heated at 25 3 . fur seven mass. partner sets

cd samples were treated at 4440°Q. 4:or lour days, aid

W4oQ.. for three (my's, tae latter tieL tieing placed in

holes in a solid copper Ulocs whion was itself heated

La a !ureace. Alia arrangement allowed very even

heating. After vent:ming in carbon vetracnioride,

the ingots were crushed, and samples from each auWecced

to X-ray diffraction in a 19-cm. camera.

it was found in the eases of all three gets,

those heated at 2.,,J°0., 4,A.1°0. acid tiot./ °C., that tne

62.5, copper alloy showed a few extra lines over antl

above those of -C-Cu Al, that 63.5 and 64.5- copieer

showed only the lines of %:tt -0 while 65.5 iihooed

both 0C

A lines. 66.5 and 67.5 copper showed only

A -Ou Go (see designations in the preliiiiinary survey

of the system).

2he parameter of the phase was calculated from

measurement of the atterna of 62.5, 63.5, 64.5, and

65.5 atonic percentages of copper. .ore (Unfit). OS to

the method of measurement and the calculation involved

is given in the next section. The parameter Values obtained are shown in the ac jtoont table. The maxi error envolved we .004 Ao.

600 Q. 406°C. Oosrosition POO° 62.5 5.725 5MS 5.730 63.5 5.725 5.725 5.72? 64.5 5.750 5.751 5.747 65.5 5.751 5.749 5.750

These showed, that, as was to be expected, the value of the okraneter for saw particular compoaltion was eithin the liait of experimental emir, opeetent• Further it was uses that the non—atoiohlometry of the

form of Ou Je is located between 63.5 and 64.5 atomic of copper.

As it was oousidered dosireable to locate these Units of nonwatotoluometry acre preeisell, three

further allois were pre ared in the sumo manner as

described above. Theo° 'one of 53.7* 611.0, and 64.2A ooppor. zaaplea of these were &soiled la evacuated ;-,/rex glass tutees, aud 'listed at 2;.4°'s,7. 11 4Q0°C., end

6.420, for ;;he sat* periods kit time as before. After quenching in carbon tetraohloride, sad subjecting to

L:p-ray diffraction, ths'lattioe parameters were measured

in eash ease. These are given together with the

#100

THE SYSTEM CuSe-Cu25e.

•

•

• • •

9oo

'7, ,

38

n1- 1

01.3

dW

3.1

.

700 C.. t.

-1-

Cu Set 6.12 5c

3 oo

(00 ti

Cu,. Se. C...1 3 5e ,

C4.1, .5t.2 tCi $e.

68 IA CutSe

44 42 COMPOSITION. $4 52 SO Cyet

iNCORPonA-rtitar TMS DATA 0F 13012c1.4ER-r.

Fly 6

velum; far o3.5 aad 64.5.4 coi*er in the accouLmaying table.

CoAipoe,itiou 2.,.; ‘i. 4,.* ,,.

63 5.72,3 5.725 ).727 zi3.7 5.726 5.725 5.727

2.737 5.23E1 5.7.5a

64.2 5.744 5.144 5.75- ,J.751 5-.774474

A plot o; lattice parsAater against cow onition

was asde for each of the three tee, eratures, znd it

was found that the non-stoichiotaetry extends from

65.'V to 64.3 - 64.4 copper. :maples of alloja of 640, 65.5, and 66.5

copper were heated in sealed evacuated Jibes tubes

at 9,:APQ. for 48 hours. ;,iter oenehiag ia carbon

tetrachloride, the ingots were crufshed, end satuplee

froe4 uhtral subjected to A-zej ;,gtkin the

104.5 alloy showed the pattern ..f the 6).5/0

alioj both thetand the 1 foros, end the 66.5 atowio

percent copper alloy oals the d form.

4,bb:blAijejjtethol ottiteailm4,4

Vili, CRIXAL,XNIRAInlY cif tliK

The only selenide Dreviouely studied in this

respeot was the oubic form of Cup', the structure

of which wan worked out by Real's Gippkiaid •fMt•ii.

1936011157.). Wring the course of the present

study, further data were obtained an this form, and

also on the tetragonal mollification, ip-Owee (horebett

Z,4rist 1945,100,5.), GuTle2 had been stated by

Uoria ,1944),L,461.) to be hexagonal,

a conclusion reached as a result of the similarity of

the pattern to that of di 44,3 which had been shown to

be hexagonal (arravano and vaglioti

19> 6%4923.).

:irhe determination of lattice oonstants fro

powder photographs neeeseitates a knowledge of the

4raKil, Owlet for each line. The values of 41 were

obtained by a method due to 3radley and Jay (trombt

noo.,1932•44,563.). rbie uses a ratio of two film

lengths, instead of one length' and thus, provided

film* shrinkage during processins' is uniform, errors

from this source are eliminated. Au using this method,

a knowledge of the distance between the low angle knife

edges, and of the reflex angle subtended by the high

angle knife edges — the camera constants — was needed.

fhetise *mantles were cal * sasaers from neasuresents of the straightdistances

the low sad high angle respectively. provide a cheek on the aceurac of t

aeats, the procedure of Lipson and wilson s,, It

Imo 194142'1440 was used. A quarts was taloa, end the e values calculated

lines tieing the experiaentaliy obtained camera constants. Couparison of these values with those given br Lipso and ilson showed a vest gaol degreeof 'Agreement, and

thos the meaeured *seers constants were satisfactory* The high angle lines on a powder pattern re the

sort valuable for the **Isolation of lattice parameters are less affected b errors due to eccentricity

of the specimen, absorption therein, end other effects. The definition of these lines on the patterns of the selenides was not good, as there was considerable

nekgroun4* attempt was therefor* made to effect

improves An this respect. Alloy* of 63*, and 0.0 atomio of copper

prepared by heating to 400* for 48 hours were ground roughly, and simples from them heated at 800°0* for hours in evacuated sealed silica tubes. A $.171

alloy was heated in an evacuated sealed Pyrex

glass tube at 6Q0°C., and 44)/ copper at 25Q0U. in

a similar container. in all cases the rate of

Gaoling following the heating was kept below 1

his value has been suggested by A. 2aylor (An introduction

to x—ray etallography. Aradon 1945.) to be such that

equilibrium is maintained in the alloy during cooling.

Po facilitate the use of such slow cooling rates, and

to ensure even heating of the tubes, the latter were

placed in 3/8" boles drilled in a copper block. The

block was eylindrioal, *bout 214011. 1011b,4 and of *bout

6cm. diameter, and five boles were drilled parallel

to the aria of the block, one in the middle, end four

equally spaced round this. he holes were about 15cm.

deep, and were lined with asbestos paper to prevent

the glass or silica ttbey sticking to the block. Tbe

latter was placed, with its axis horizontal, in a

nichrome—wound furnace. the high heat content of

such a bloc* enabled small step.wise adjustments to

be made to the furnace current without effecting the

=oath slow cooling of the samples in the block. A

thermocouple was inserted in the middle bole, and the

samples to be treated at any particular temperature

in the surrounding boles. Very considerable oxidation

of the block was noted at the higher temperatures

Cs33412, ow its decomposition at a

low temperat was not amenable to annealing

treatment, and the aatevial es prepared was used.

A 19-.es. 00110r* Was w104, and X-ray diffraction

patterns taken of all the alloys. It was found that

while sone sharpening of the high angle lines had

occurred, in general, annealing had not greatly

improved the patterns. An except 63.% copper were taken with a nickel filter in the camera. This

eliminated A radiation from the copper target. Uoth

and A reflections were present on the pattern of

63.54 copper, end using the fact that the II reflection

from anyc rystal plane has an intensity about half

that of the 4reflection from the same plane, and

also using therelationships—

. / se A 2s sin

an

it arse possible to distinguish between the two types. Pros the values of for all the 0( reflections,

values of An.% were oaloulated Then fOr each

al *rites there exists a relation between the

Alll.cr indices of a crystal plane, the lattice parameters,

and ain.

plane.

For a cubic vets

tetragonal

2

4 b o 2

x

h2 ik

in. d- 4a

st for the other crystal systems,

splez for general use. The identification and calculation of lattice

parameter for a aubia crystal is quite simple as,

since it, k, and I are integers, all the values or

6in. aro multiples of a certain imminent corres-

ponding to the value of in. 441 when OA 12 is one. In the ease of the hexagonal or tetragonal systems,

there are too imminent* in sin. , one corresponding

to the 'a' parameter, and the other to the 'oft and

since any value of An.% may be composed of multiples

of either or both inorenents$ the process of indexing

is more difficult, especially so as all the possible

reflections are never present. For oration of two

parameters, graphical methods have been devised by

hexagonal

Rui.I vex (an. .19214205490 and

8jnstro* (Z4.assVik,19314t2,346.) but of those

only the logarithmic fog of the Nurstrom method

is satisfactory in use over a wide range of axial

ratios, and the curves required for this must be

plotted on a logarithmic scale.

when there are three parameters, as in the

rthorhosbic system, charts egnnot be used, and trial

and error must be employed. Consequently very great

difficulty is encountered in indexing a powder pattern

of this type, and single crystal methods are usually

used.

The pattern of 63.5Z copper being cubic was

easily indexed, sad little trouble was experienced

with 67.c% copper which was found to be tetragonal,

and the indexing of these la shown overleaf.

-102-

-Ou So ,E) era 2 5n.A.

• Mc filter. empostare.

Iritonoit7 sin2 (Gala.)

1 4 12.6 .0437 A

2 7 13.39 .0538 1 1 1 3.323 3 5 nirt es.,,,,,,.. • 1110 A 4 10 22.2? .1435 2 2 0 1 2.03; $ 2 23.70 - .1606 B

6 5 26.3? .1973 3 1 1 1 1.732 7 1 29.07 .2360 1 8 1 32.01 • 2810 11 9 3 32.49 .2885 4 0 1.432 1Q 3 35.76 .3419 3 3 1 1.316 U 2 36.45 .3528 1 12 5 41.06 .4314 4 2 2 .4322 1.171 13 11 44.22 4865 5 1 1 il 4862 1.1u3

3 3 3 14 1 49.3`9 .5763 4 4 0 .3763 1.014 15 1 52.54 .63f 31 5 3 1 .6303 0.9170 16 1 58.13 .7211 6 2 0 .7203 0.906 17 mil.1i5 .773 5 3 3 .7743 0.874

Indexed on the cubic afatoa giving a • 5.734 A"± 0.005

radiation. Si filter. 3 boars eapesure.

h k 1 sin 0. (cola.)

6.53 .o3.29 3. 1 3. •,..1133. 6.720 12.67 .448Q 3 1 1 .0482 3.512

13.17 (319 2 2 2 . 424 3.377

19.34 «1096 5 0 0 *1096 2.324

19.87 .1155 3. 1 5 .1168 2.263 1 v .3.141

21.631 .1359 *WM oar 2.L86

21.98 1401. 4 4 2.056

25.84 .1899 2 0 6 1.766 30,59 • 2589 7 3 1 .2589 1.512

31.71 .2783 0 o 8 .2765 1.464

:34.53 322.3 5 0 7 • 3214 1.357 35.16 3316 6 2 6 .330 1.336

36.35 .3513 8 4 0 • 3512 1.299 40.54 4225 6 5 6 .4231 1.184

42.74 46c6 101 2 .464 1.133

43.37 .4717 6 6 6 .4716 1.120 118.55 .5618 8 8 u .5619 1.027

51.40 .6208 10 2 6 .6121 • 985 nel /votes giving •

Aft 11.7 e/a

latensitr

3. 5 2 5 3 6 4 1

5 7

6 1 7 lo 8 7 9 1 10 1 11 1 12 1 13 I 14 1 15 1 16 1 17 1 18 3. index on the tetrogo

11.6

of the other three

awerise to the impression that ttese were

► three parameter type. AS a result of very prolonged study by-what may

be termer systematio trial and error, this impression

was confirmed in the cases of Ogee, and Cu a2 and

these were indexed on the orthorhombic system. CuLie

ultimately proved to be tetragonal, but had a large

axial ratio,, and was thus not *sally amenable to

graphical solution. The indexing of these three

comiounds is shown rime.

-lOS-

OU""2 .p.'.n 80.114'1. Cl&& ..aUdio•• m. m,.l'•1S-.A. 5Ok.'. J boUtS exp08\lM.

lAt""7 (; ab'". J1 Ie 1 aiJl2e d(calc.)

1 3 I.ao .0203 1 1 0 .iJl97 ,.",2 1 10." .032' Q 2 0 .0)20 4.269

J 8 12.118 .0ItfI1 2 0 o .Q1M58 '.5614 , 1J.24 .On4 \) 1 .2 .0'20 ,.,", 1 13.92 .om 2 0 1 .oS78 '.203it 5 14.)3 .(.61' 1 1 2 .()6)7 '.109

? 4 15.56 .0119 o 3 0 .0720 2.868

8 1 16.66 .Ul22 0 J 1 .0850 2.683

9 1 16.'2 .0847 1 3 ;;.> .C8)? 2.M4

10 J 17.48 .0902 2 « 1 .0898 2.562

11 1 18." .1012 0 0 , .V990 2.418

12 1 18.92 .1G51 ) 0 (j .10') 2.''''IJ 6 19.90 .11.59 v J 2 .1160 2.260

14- 1 2{).5J .1U9 2 2 2 .1228 2.195

l' .. 21.10 .1296 2 3 1 .1298 2.131

16 S 22.111 .1_ a (I , .1458 2.021

17 , 22.67 .1....' ~ 2 1 .148J 1.996

18 '" 22•• .1524 2 1 J .1'38 1.911

19 , 2'....., .1_ , 1 2 .1513 1.9"

20 , 23-8' .1631 2 , 2 .1628 1.905

21 10 a-.93 .1717 2 2 :5 .1778 1.826

22 9 2'.• .1818 1 () ,. .1877 1."'

7. (tont.)

k 1

3 2

5 0 1 3

2 5

0

2 5

3 0 6 2

6 0

4 4

0 0

7 0 2 6

7 2

2 0

3 2

1 ?

1 4

4 2

8 2

7 3

3 5

23 2

24 1 2

25 1 4

26

27 2

28 1

29 1 37.12

38.58 2 3

31 1 38.84 3

32 3 39.77 1

33 3 40,47 6

34 2 41 V 2

35 3 42.30 0

36 1 43 47 2

37 1 01 6

38 1 09 6

39 94 0

1 49.38 7

6

42 1 2

43 1 3

44 2 6

.2213 1.637

246a 1.550

.2942 1.420

• 3070 1.369

• 3218 1.357

3298 1.339

.3643 1.275

3888 1.233

.3933 1.227

.4093 1.203

.4212 1.180

• 4368 1.163 .4532 1.143

4828 1.318

4932 1.096

.3372 1 051.

1.036

•5796 1.010

.5932 0.990

♦6128 0.983

.6363 0.965

.6683 0.944

,

-10?-

7• (0010‘)

k i

45 1 57•40 8 4 1. .flQ2 0.913 46 1 511638 .7251 6 4 4 .7252 (.4 904

47 1 6Q.43 4565 8 1. 0 •7568 0.885 48 1 62.1 .7855 2 5 7 .7959 0.868 49 1 70.14 .8M6 6 6 4 .8850 0.818

5,4)I ?3.9c' .9444 5 9 .9405 0493

indommi is slieboxerable giving it-

ap7.11:02, ee los$4.60:*01A0. ,st )01.01 Ae.

2 5 4

6

9

13 34 15 1

18 19 20 21 22

re as y5. A. 5‘11t.V.

Z*$*nsit 0AU k 1

1 3• 31 • 0530 2 1 3 14.41 .086 1 2 1 14.42 •04.19 3 34.87 .0655 3 3 5 1544 420 8 1647 • c1114 33

1649 .4134 Q 22

3 14.55 .145 331

3 20.95 .1279 4 0 10 2246 •1521 3. 2 2 23.79 .1626 3 3 4 24.31 .1694 1 4 3 23.02 a178" 4 2

3 25.24 4616 0 0 4 26,40 .1988 500

5 26.88 .2014 2 4

3 26.35 .2255 2 1 1 26.53 .2261 4 3 3 26•90 2336 34 6 30.30 • 234) ) 0 4 )).21 .3323 3 5 2 53.430 0422 5 2

41

1 1

2

0

3 0 * 1 4

1 4 1 0 4 1 3

.0535 3.343 0596 3•161

3*(83 39 2.99?

• ano 2.066 u.c2o 2.699

• v669 2.633 .1096 2.379 .128v 2.153 •353.5 ulna

.1822 2•511 4663 1.666 .1793 1.620 an 1.805 •204)0 1426 .2038 le7C2 .2255 1.62o .2296 1.611 .2323 2.592 .055 1425 .3340 1.336 .3433 1.315

•3 .4035

4129 4209

.434

.4442

1.220 1

.4814 10,109

.4822 1.107

.4936 1.097

.5014 1.085 5124i 1.76

5368 1.0o

«5448 1. o43 .5620 1.1,326 .5801 1.009 5980 0.997

.6101 0.965

.6311 (4969

.6527 c•953

.6662 Q.944

.6842 0.934

.6951 0.923

5 1 6 6 6 1

3 0

1 1 0

2 2 7 7 2 7 6 1

3 7 2

. )

b k 1 oin Coale.)

24

25 26

27

30 31 32 33

34 33

36

36 39 40

42

43 44

• 2 1

39.06 .•~wrr,.

3 7

2 0

1 .4122 0 u

1 .42(38 1 O

1 .4300 1 1

1 .4436 3 6

1 .4808 6 3

1 (.4829 7 3

1 .4918 7 3

4 5024 u 7

3 40.66 5114 8 0

1 47.15 5N5 7

1 47.53 • 3441 1 7

1 48.60 is 5627 LI 0

1 49.67 5812 1 1

1 50.56 • 5963 8 2

1 51.46 .6119 1 2

1 32.61 .6313 4 3

1 53.86 3

1 54.65 .6652 3 7

1 55.83 6846 2 3

1 56.4? 6949 1 8

110-

(coat

20. h k aa20« (sale.)

1 02 9 0 •7493 1 7 6 1 .7642

1 ? 0 5 .7e09

1 5 1 ? •7721 .811.6 lo 0 1 .8115

1 .8194 1 9 .8196 0.850 1 .8238 o 9 1 .8231 .848

1 .8401 108 .8401 (.4840

1 6646 .8443 2 9 .8438 .837

1 71.25 .8967 3 8 4 .8968 x.813

1 72.02 •904? 7 6 •9u39 x.809 1 72.53 .9099 9 5 1 .9100

77.25 .9513 6 5 6 .9514

79.81 988? 0 2 9 .9891

1 84.93 •9753 9 2 5 .9748 0.779

1 81.89 9801 4) 1 9801

•R8.622.01 4-7.691. £?.

45

46

4?

48

49

So

51

52

53

54

55

57

$8

59 so

ladozod o

-111- C41841 a rao.29ce. Gs g ractLetion. 01 tilt?

'Oka* 3 boors inoestisit.

istessitr0 *LOC

1 1 10.42 .0327

2 3 12.47 .0466

3 1 13,0 • 05(Aii

4 4 1347 027

5 6 Pie OW

6 1 14.32 .061.2

7 3. 14.87 .0659 8 1 15.2) .068?

9 10 15.53 0717

10 1 17.50 .404

11 2 19.90 .1159

12 2 20.54 .1231

13 2 20.97 1a1

14 5 22.66 .1484

15 6 22.99 .1525 16 1 23.82 .1631

17 7 24.96 .1781

18 2 25.68 .1878

19 1 26.6? • 2001

20 1 27.00 .2f.;61

21 1 27.44 .2124

i2ø. ei )

.0524 4.254

.0466 3.563

.0501 3.413

.02? 3.353

.0578 3.178 • 0612 3.111 • (*38 2.997

2.955 *0721 2.874

.0/95 2.557

.116? 2.260

.1213 2.199

.1282 2451

.1470 1.99?

.1551

.1631 1.905

.1? 1.824

.13118 1.775 •2.'.4)3 1.720 • 2069 1.695 .2115

k

O 0 4 2 0 1 O 5 2 0 2 2 1 1 1 Q 5 2 1. 2

O 0 6

2 2 0 2 0 6

2 2 4 U U 8

5 2 1 3 2 2 3 2 5 4 0 0 402 O 0 3.0 2 0 9 1 0 10

1 6 .4830 1.104 3 Q 05022 1 .086 U 16 .3128 1.075 1 U. 4325 1.055 0 5 .5969 0.996

3 3 •6653 0.943 3 1 .Oea 431

.7182 0.910 .7940 664 .8501 0.835

3. 2 18 4 14

awl* litters nos a

omit/ h k 1

* 2 * 0 6

3 1 9 1.466 (i) 12 • 2884 1.434

5 1 1 .2921

3 0 10 300 . 400 4, 2 2 U .3316 1.336

3 3 9 4631 1.275 4 3 .3752 234 1 10 • 3900 1.230 0 2 .4098 1.20Q u 9 • 4412 1.15?

22 3 23 1

1

25 1 fi t

a? a 28

29 1 30 1 31 1 32 1 33 3 34 2

55 1

36 1 1

38 2

39 2 40 1 41 1 42 1 *3 1

.3759 4 6

5 .4852 6 447 6 51/7 0

46.83 .5319 5 56* .5966 7

54.6? .6656 7

55.79 «6839 6

5? ?5 71.33 8 65.03 .7949 3

67617 .8494 5

QuO. Vattern no. 290. (coat.)

el

74.76

?9.34 06

k3L1241. k k 1 Maga. (ewls.)

.9310 6 6 8 4317 O.

«9613 9 0 6 .9662 41•78) .5702 0 0 22 .9695 0481

Indared on tka tetragonal wales Wins z

111.7.2801 .01 047.2011 .ca A0. 0802.3,

Intensity

44 1 45 2 46 1.80

446011/38110114.

114-

4p,g170,4 ixt _ DPVtIsalois

he system reaulting from the present

study in shown in fig.?, and the only previous werk

on this topic is represented diagramatically in fig.%

(1) Accuracy of measurements made

(a) Low temperature thermel analysis.

In so far as the determinations of the meltint:,

point of practically pure selenium are concerned, the

question of accuracy hss been discussed when deolinG

with the actual valuet. obtained, as upon this depends

the si ificszce of the variation noted in the meltins

point. figure of o W4s deduced from repeated

determinations on pure lead, and in the 11 of this

figure the above-alentioned variation was found to be

significant, end the appropriate interpretation made.

t. quite considerable source of error in these low copper conten alloys is likely to be found in the

preparation* 44 about 55, of selenium was weighed

out, for a 0.254 copper alloy, on error of up to 51,

could easily have occurred in weighing the copper.

qpile this is not in itself of major significance when

considered with respect to the rest of the system, it

does seem to preclude an accurate determination of the

2 A-145.

Cu + Se-

9 00

700

-1

Ti

rn

rn

(00

300

1100

THE S YS TEM Cu —5e.

2 Li ou iv

je

Gus( 4- A.isTorD

Cu Se *

Lu z Se, + Cu Se Q

Cu, Se,

100 Cu 20 40 COMPOSTT7 ON 6o

AT.-%

Cu a Se, + Se

BO Se

A -rofrucZ Se

1160 O 3t •to 10 1

114-0

1120

1100

ji 0 80

cr 1060

"(1040 4.1 0. W20

14J

Z LIQUIDS \ Cu2.5 e. 1 ,

1107 .C... ,.. W

, LiQuip , 4- , , , , , cu,..se. ,

\I _1063-c.

1000 Cu 4- Cu, S e

4670

960

'7+0

920

Cu (o ;0 30 WT 7 Se'.

g.

4-0

SO

I 5-

position of the eutectic as the latter lies so close

to pure selenium.

for the sealed-tube type of thermal analysis, a

good conception of the accuracy of the set-up maybe

obtained from a conaideration of the figures obtained

throughout the range of existence of two liquids. These

show that the values for the position of the halt at

ca.523°f3. may be covered by en error of = 2°G., while

in the case of the halt at the lower temperature, with

one exception the NOXIMUM variation is 10C. It would

therefore seem quite safe to say that the accuracy is

covered by an error of = 2°C.

.A‘rors in the preparation of mixtures for analysis

do not of course have any effect within the limits of a

miscibility gap. Outside this gap, the compositions

covered by this method of analysis were such that about

equimolecular amounte of copper and selenium were

required. In this case, when quantities of the order

of 2cg. are being weighed to three places of decimals,

the error introduced is of such an order es to be

totally insignificant.

,hen the copper-rich end of the system is

considered, the temperatures being higher, there ie

-116-

more difficulty in obtaining an accurate value, end

the error is consequently greater. .t11) 4kaguitude of

this error is not amenable to precise determination,

but as before, it ueems that a fairly reliable value

may be obtained by considering the values obtained

across a miscibility gap. These are all covered by

an error of 0 4 0. AS pure copper is approached, the errors

introduced in dealing with the preparation of alloys

increfise. ; no measurements were wage on very high

copper content alloys, however, no serious error is

likely to erise from this source.

The particular difficulty introduced by the loss

of selenium by volatiliastion has been considered in

connection with the Qelts in the system Cu e

these being especially affected.

Awn chemical analysis has been carried out to

determine the liwite of a miscibility gap, it is not

in the actual analysiu thet the main error lies.

error involved In an analysis is not usually greater

than I part in 5W. The source of error is contesication

of the material analysed. This contamination may be

due to several causes. here ray De currents in the

preventing sharp separation of the two layers;

the containing vessel may have a surface effect on

one of the liquids causing creeping; whichever layer

solidifies first may contract or crack, and allow

penetration of the still liquid layer. All these

sources of error cannot be estimated, and while ever'

effort may be made in selecting the sample for analysis

in avoiding obviously contaminated material, this risk

cannot be entirely eliaiinateds .:onsideratiou has

been given to the possibill.ty of taking the composition

of one layer formed in the presence of small amounts of

the second layer, and plotting this against the overall

composition of the alloy and extrapolating to the point

where the second layer di sappears. /application of

this prinoiple to the figures obtained in the present

work showed that it is very doubtful whether any

definite relationship exists between the overall alloy

composition, end that of the predominating layer, and

for this reason the idea hes not been pursued.

The extent of the non-atoiohiometry of ,Cu f*el

has been determined by the measurement of lattice

parameters of the cubic C) phase. ale usuel method for

obtaining accurate values of the parameters of a cubic

phase consists in making a mathematical or graphical

-118-

extrapolation of the value of the parameter to the point where ,lAr320 a 1. This method eliminates most of the sources of error (Oradley and Jay,Aroc.D2zE.

oc., 1932,44 5634 1933ctt1.5c7.). This linear

extrapolation is, however, only operative for fairly

high values of 0, but owing to the nature of the

pattern given by ou2 4, it was not in geueral possible

to obtain such values. The method therefore adopted W89 to work out the values of the lattice parameter for the highest five lilies which could be measured,

and to take the linear mean, and to conaider the error

ea the MeZiMtigi requi.,sd to cover the values obtained.

A comparison of the values obtained for the same alloy

on samples quenched from different temperatures showed

that this procedure covered the errors encountered. To ascertain the non-stoichiometrio limits, the mean values obtained at any one temperature were plotted against the composition, and the limits of the change of lattice parameter noted. The error considered possible in these limits is of the order of on

the compooition.

In cases where non-cubic crystals are eovolved,

there is no fixed procedure for determining accurate

lattice parameters. oohen c.ev. iost 1935,6 68.

-119--

hoc cut forward a mathematical procedure, but this

demands very considerable accuracy in the 0 values

for the high angle lines. .;wing to the nature of

selenldes, the patterns ootained ere not of eufficiently

nii8a standard to enable this requireaent to be viet, so

tnia vrocedure was not adopteas ale metood usa6 was

to consider the tea lie of hi best 0 values, and

adjust the parameters so that the fluctuations in these

are at a minimum. can value for each perameter was

then found, together with the error required to cover

sll the values obtained. 2rom the saran parameter

values, values of .-An.w+ for each line lore calculated,

and these were compered with the experimental values.

in any case where the agreement was not good, the

whole was abandoned, end a fresh start made. :his method is entirely empirical, and cannot be expected

to lead to a a:athematic:ally correct aseignment of

possible errors. It does, however provide some

indication of the degree of correspondence between

the chosen crystal and the actual data obtained from

the powder pattern.

Itilising the trial and error method for designation

of crystal syster and approximate lattice i)arameter for

sn unknawn pattern, it is not posoible to state

categorically that the chosen system and parameters

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are the correct ones to the exclusion of all others. It le possible that other combinations of lattice

parameters would give reflections in the positions

of those found. An cases where a considerable

number- in many cases forty or fifty - linen are

fitted to one crystal system and one set of parameters,

the chance of an erroneous set of values being chosen is very much reduced, and may be considered very small.

Gorrelation with work previouslyo..... zazttLeute , redetermination of the systems Cu - Oui.4 hes

been made. Me original work of :riedrich and Leroux

( etallureft,19v8, , 355.) cannot be considered to have

done much beyond establishing the vftneral form of the

diagram (see fi 8). this form has been retained,

but the temperatures of the eutectic, the solidification

of one of the liquid layers, and of (:22!;e have all been

lodified. This modification has always been le-is than

2.Pc. ?he error on the original work was given as = 1 0.

'hat some modification should have been necessary is

not surprising when the set-up originally used is

examined. Ole main respect in which, this could have

Peen claeoed as faulty is that it lacked any really

certain method of avoiding oxidation of the melt. he

121

crucible containing the alloy was positioned in the apace surrounding the carbon hiating rode, end it was considered that any air les►>king through the refractories would attack these, forming carbon monoxide and carbon dioxide, rather than oxidise the melt. it was also assumed that carbon monoxide and dioxide had no effect on the melt. ../mile this latter postulate is probably correct, it is not difficult to conceive of some oxidation of the melt by ai leaking through the refractories.

in addition to these redetermination*, a more accurate determination of the euteotio composition can now be made. eriedrich. and Leroux gave a value of about 1.5;4 selenium deduced from an extrapolation of the curve on the copper-rich side to the eutectic temperature. tie stated above, the new estimate of

is based on an extrapolation of the curves on both aides of the eutectic to the point where they intersect. A check of this is furnished by the fact that this intersection Lies at the eutectic temperature as found frna a number of laelts.

The extent of the miscibility gap, previously unknown, has been determined by chemical analysis of

122-

the two layers. "live difficulties in the accurate interpretation of the results hems been mentioned above. it has also been possible to obtain, by thermal analysis of an alloy of 0.22i, selenium, a point on the liquidus carve between the eutectic and the limit of the miscibility gap. the melting point of Ou previously given at 1113°C. is now at 1i:49?

The shape of the liquidue curve for the On system is Andlar to that obtained for the system As - ;1. by (Gamz..itel.,1915,4A,533.).

*)th show a compound Maas, and have a miscibility gap on both aides of this. the Ag2se miscibility gap has its upper limit of composition above 5 silver, so it is difficult to conceive of sive, reported in the literature, behaving as does iJuse. It say of course be that Aga* dodo poses at a temperature below that of freezing of the silver-rich liquid layer

in this case though, one would have expected this to be detestable. does not locate precisely the selenium-rich end of this miscibility gap. The lead selenium system (1=.41etbon, citmt.'1;end.,1912,121.1414.) is similar, but in both these cases the selenium-rich eutectic is placed at the same temperature as the

.oeltins T;oint O ti gieleniux. bile thi, suf,,,e3ts

that the systegis are of tho ;=otestie variety, tials

a6y l!ell not e the case, as the ex2erkulental rrs,,,ie-

c,lents used were not sufficiently -'ensitive to hetect

the siimall temperature differences involved. A is,

however, worthy of &motion that the silver - sulphur

systea recently studied by ,:rec. (Trens.,zer. eokhysics

,Jnion 194642064.) also shows a caonotectic type.

,hile it is doubtful whether the temperature recording

system would have been sufficiently sensitive to detect

the small change involved, ',racer utilised a technique

capable of giving the ooaposition of the sulphur-rich

liquid layer with a considerable accurvey, and was

unable to detect any silver therein.

The value taken for the tielting point of copper

in the present work mu used as a cvlibration point,

and conaequentlr no significance may be attached to it.

0:oceoure seemed justifiable In view o the very

pure (kkreeter than snectroeconically pure) natuTe oT

the copc,er. ,he meltinc; point found for selenium come,

after calibration correction, to 216.7°',3. Adis compares

fsvorebly with, values of 211°0. by luertler nnd ,irami

etallirundo, 1,A9,11,1.) end .ondein and onval

124--

comt,.!',iend.,1926,182,1465. 11 Chita., 1926, 2,1349; 4°,11430, and of 217.4°C. by Dodd (i• Amer. Ches.42., 192u,R,1579.).

,ith regard to the temperature range over which is stable, previous workers have reported that

this compound decomposes at around 17,PC. .4 .;fr •

khYeik • C12001.13. • 11.936cno 157. Goria, Gessz.ohinuitel

194`,L:,461.). 'neither of these workers claimed to have made en accurate measurement of the decomposition temperature which has been shown in the present study to lie et 13Q°0. ilehlfa also claimed to have prepared .030,2 by direct union in the liquid state. 'Phis is not easily conceivable, but it is noticeable that he makes no reference to quenching of the specimens, end the Cu3 fie2 mey have been formed on relatively slow cooling. Anthers if in fact the specimen was quenched, it is probable that a considerable amount of CtE.3e was present therein. This amount might well have been sufficient to bring out the weeny lines on the pattern of this compound. and this would have wade it difficult to distinguish. between Cu3se2 end a mixture of CuLie and Cu2Set by a mere qualitative examination of films taken on a small radius camera such so that used by

-1 5

is more erpecially true ea an lines

are common to the patterns of Cue and

assumption that no quantitative exnaination of the

films was nude by .Ethlfs is based on the lack of

quantitative data in his paper.

s a result of the plotting; of the system, it

hee not been possible to oonfirm the deductions of

i:'61abon (ComA.rend 1912,311,1414. )9 who found from

azoureifients of tae of the cell :;,'IuicAL,:-Li ;Et

that Cfla , e was the only selenide stable at room

temperature.

einhold and Wiring (2..pb,sik ham•Li

221.) stated as a result of conductivity measurements

that the non-stoichiometry of CuaLTe previously reported

b. ► Izahlfs (l.c.) existed at least dory to Gu1.6.,_e,

i.e. 61.5 atomic capper. in the present wor # the

lower copper content of the c,4 form renle of existence

h s been located, ss a result of measurements of

lattice parameters on quenched specimens, at 63.7,,

copper. )oth ,i,thlfs and .,1orchert ('•riat.#13ig4 1 #5.)

have found that the 0C # cubic Cormexiste right up to

the stoichionetric composition at tent9eratuze of 120 Q.

and above. Blow the transition point at 110 tlis

tetragonal 8 form crag found by Aorchert, who also

-126-

found that the transition temperature decreased with decreasing copper content, reaehing room temperature at about 64.34 copper. both these workers used high temperature castrato. :the present study, using quenched specimens has railed to obtain theo< phase with more than 64.3.:. copper. iortween this and the stoichiametric esosposition a mixture of .0 and A phases has been found, and above the stoichiometric, only the I phase. it bee been stated by borell (.1net. ,1944,21t0435.) that the o phase is not retained by quenching. This would explain the findings in the present study, as the upper limit found for the non-stoichionetric range coincides with the composition at whichthe transition temperature reaches room temperature. 3n the other band, F_ahlfs found just this type of behaviour for Cu using a huh emporature camera. s :ehlfs and 6orchert both give a parameter ms5.8C,j0., it seems clear that they were not misled by lack of knowledge of the composition of their specimens. ::.upport for the assumption that the divergence in findings is due to non-retention of the oZphase on quenching is furnished by the fact that specimens quenched from

show behaviour similar to those quenched from

127-

a lower temperature. For if the two forms ere capable of simultaneous existence separated by a two-phase region, there should be two maxima 013 the melting point curve. This is not the case, and 9o0°C., is sufficiently near the melting point of a 64.3;'6 copper alloy to eliminate the possibility of the disappearance of one of the phasea between thin temperature and fusion. Thus it seems that only an investigation with a high-temperature camera can completely study this nonwstoichiometry.

Nith regard to the crystallography of the selenides of copper, the form of Cu was found to give the sear pattern as that of :4021fs and Liorchert. vim I fors indexed by ilorchert as tetragonal, hes been indexed before the availability of Oorchertes paper in this country (C.A.$1948$42,1i49.)• The parameters obtained are of the same order, but not identical.

liorchert does not publish any numerical date, but gives a diagrammatic representation of the pattern

obtained. This shows sharp definition of relatively close lines towards the high angle end, even though the pattern is *aid to be of poor qualit'S Also the pattern obtained showed a few extra lines as compare

-128-

with Dorchert's.

in the case of Cu 3e 9 Goria (1.c.) EiVeS a

very poor reproduction of the pattern obtained in a

5-cm. camera. As for as can be seen from this, the

pattern obtained in the present work is similar, but

owing to the lack of numerical data in Aria's paper,

nothing definite can be stated on this topic.

suggested that Cupt2 was hexagonal. This was based

on a similarity, between the pattern he obtained, and

that of Bi 724. obtained by Parravano end Coglioti ( azz.

chimital.,193J,6t11,923.). it is to be hoped that Toxic

had access to the original pattern, as the paper of

iarravano and Caglioti gives only a. poor reproduction.

urther, examination of the numerical data given for

Bi2' Se3 gives rise to grave doubts as to whether in

fact this substance has been correctly indexed by these

norkers. Thus it is not at all surprising that Cu5: e2

is found to be orthorhombic, and not hexagonal. he

assignment of a cryntal system to one compound as a

result of a similarity between its powder pattern, and

that of a substance of known crystal system is not a

procedure to be recommended. ;,,or unless the axial ratios

of the two crystals are similar, and these possess the

same systematio extinctions, then two crystals of the

2

same *rates can give patter** which appe#r to be entirely unrelated.

The reseereh bora itkaaasibalt was Riau

a tine when the writer was in receipt of * sintonanos allowance from the 1;epartnent of

+read Industrial Research. $1tbaut this, no mob stud," coutd have been made.

• be writer wishes to thank the feasor 11.V.A.brisco* for the research a d. indesowariscoess kindi interest end

have been warmly appreciated. 4pecia1 se due to iv.Albj.11;4041ch for his extreme

giOrie

use has been mad* of the X—ra equipment

by a rant from the T:oyal society' to erofessor

e and r. =elch, sad greteful recognition in given

fsoilit es provided.

2 4Z.4-eij6

AUgUat 1949*