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LECTURES ON CHEMISTRY,BY

PROFESSOR BRANDE.

Delivered at the Royal Institution of GreatBritain.

LECTURE XL.

On lVle),cury, and its Compoitnds.THE next metal on our list is mercatry,

which is an important metal in many re-spects, but especially on account of its ex-tensive use as a medicine. I shall occupyyour time this morning in stating to you, thenative sources of the metal, the mode ofobtaining it in its pure state, and the prin-cipal combinations which it forms with othersubstances.The most productive source of the metal

is the sulphuret, or the mineral called cin-2tabar, but it does also occur in the purestate in the mines, where the sulphuret isfound in small globules; but you must notallow yourselves to be deceived by thedealers in minerals, who pretend to sell youspecimens of the native metal, since nothingis more easy than to sprinkle a little mer.cury over a piece of cinnabar and to collectit in the crevices of the stone. You mayeasily understand, however, that it may oc-cur native in this state, and in some of themines a considerable quantity of fluid mer-cury is collected, by placing vessels so asto catch the drippings of the metal from therocks. The native sulphuret, or cinnabar,notwithstanding its extreme density and itsstate of high aggregation, is frequently crys.tallised and transparent. The mercury isobtained by distilling the sulphuret withiron, or lime, or by a careful kind of roast-ing of the sulphuret; and if it be roasted,with exposure to air, the mercury is volatilis-ed and condensed in long pipes, and in thisway it is obtained in large quantities. Thereis only one other native compound of mer-cury, which is more a matter of interest tothe medical man than the chemist, and thatis the native calomel, or a true chloride ofD.ercury. _ _

With the metal itself you are already fami-liarly acquainted ; it is of a brilliant whitecolour, having much of the appearance of sil-ver, and, from its being fluid at ordinary tem-perature, it was called quicksilver, argentumMMM?:, and, at present, hydrargyrum; it issolid, and malleable at 10°, and, at about670°, it boils, and becomes converted intovapour. The weight of the metal is 200, Iand it enters into combination with oxygen

in two proportions, forming a protoaideand aperoxide.The protoxide of mercury is composed ei

one proportional and one, giving 208 as hequivalent ; it may be obtained by precil,i.tating the nitrate of mercury with an alkali,or from a mixture of calomel and lime water;but it is difficult to procure the black, or the

’ protoxide, in a pure state, and it is singularin this respect, that it holds its oxygen bya weaker affinity than the peroxide, thatcontains two proportionals of oxygen, whichis contrary to the general rule. It is nearlyinsoluble in water, but soluble in the acids,forming a peculiar class of salts, and thisoxide assumes a crystalline form. If youdigest the metal in excess of nitric acid, you

. ’ obtain a solution, from which, by the addi.tion of an alkali, you may procure the per.oxide, which will be thrown down of a yel-low colour, and will become red on exposureto heat. It is composed of one proportionmercury 200, and two proportionals of oxy.gen 16, so that its equivalent is 216. Itenters into combination with various acids,and forms a class of salts which are all acid,

If you take either of these acids, and applyheat to them, the ultimate effect is to reducethem both again to the metallic form; andyou formerly heard, that it was from thissubstance that Dr. Priestley first obtainedoxva-en.

’

We shall now pass on to the compoundwhich mercury forms with chlorine. When

mercury is exposed to chlorine in excess, aperchloride of mercury is formed, and if youtriturate the perchloride with metallic mer-cury, it is converted into a pi-otochloride ofmercury. Here is the perchloride made bythe direct action of the chlorine upon mer-

cury. and here is the protochloride obtainedby triturating’ it with the perchloride, andby applying heat.

, In obtaining the protochloride, or calomel,for medical purposes, the pharmacopoeia di-rects, the trituration of corrosive sublimatewith fluid mercury, and ’that it afterwardsbe sublimed three times. Formerly the sub-limation was repeated fourteen or fifteentimes, and it was imagined that the subli.mation gave the calomel blandness, or mild-ness, and hence it was called mercurius diil-cis ; at one part of the operation it wascalled dracomitigatus, giving the name of draroto the corrosive sublimate, it was also calledaquila alba, or the white eagle, but calomel isthe term by which it is now generally dis-tinguished, and it is a very unobjectionableone for common purposes. In one of the

pharmacopoeias, it was called hydrargyrummuriatum 7?zitius, and corrosive sublimate wascalled hydrargyrum muriatunz so that if, byany chance, you left out the word mitius,the one substance was used for the other,and this was done in one of the old editions.

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It is very inconvenient to alter pharmaceu- tical terms according to the changes in che-mical nomenclature, and, as physicians inpractice have not come to accord on thisparticular, I can see no objection to theterm calomel for the one substance, and cnr-rosive sublimate for the other, pharmaceuti-cally speaking. Chemically speaking, wecall the latter, the perchloridum hydrargyri,and the former, the protochloridum hydra!’.gyri. Instead of which, some persons callthem the muriate and the oxymuriate, whichis decidedly improper, because there is noevidence whatever of muriatic acid beingcontained in these substances ; they are chlo-rides and not muriates of mercury.One of the best methods with which I

am acquainted for obtaining calomel, con-sists, first, in forming a protosulphate of

mercury, by boiling mercury in sulphuricacid and adding excess of metal, and heat-ing the protosulphate with common salt.This process furnishes calomel in consider-able quantity, and, if properly conducted,corrosive sublimate is not formed. On thistable you see I have set down the sulpliateof mercury 248, and common salt 60, whichare their equivalent numbers, to show youthe weights of the materials required. The

consumption of calomel in this countrybeing very considerable, and a large quan-tity of it being exported to the East Indies,it becomes an object to obtain it as pure aspossible. Now, if we take these materialsas dry as possible, and triturate them tho-roughly together until the globules disap-pear, and then submit the mixture to heat,we obtain calomel, which should be washedin large quantities of distilled water, andafterwards be ground to a fine impalpablepowder. Now, common salt contains 36

parts of chlorine, which combines with 200parts of mercury to form 236 of calomel ;and the sulphuric acid combines with theoxide of sodium to form sulphate of soda ;thus, you see the importance of a table ofthis kind, of proportionals and numbers, tothe manufacturing chemist ; because if themanufacturer finds, that from 200 parts ofmercury and 60 of common salt, he getsless than x36 parts of calomel, he may besure that there is something faulty in thepreparation. It is manufactured in largequantities at Apothecaries’ Hall, and, bythe contrivance of Mr. Hennell for sublim-ing it, we can get within five or six poundsofthe proper quantity. If you sublime insruall vessels they get very hot, and calomelis deposited in a crystalline state ; but ifyou use spacious subthoing vessels, madeof good conducting materials, and there isnothing better than sheet iron, you will findtht the calotiiel, as it rises, falls down inan impalpable powder, like a shower ofenow, and it then requires nothing more

than washing it and levigating it, to obtain itin a state of minute division, and it is one ofthe great secrets of the sublimation to havea large vessel. Messrs. Howard and Jewell,of Stratford, took out a patent for the sub-limation of calomel ; in their process thecalomel was at once received into water.This is a very good mode of obtaining it,but not better than the one I described toyou.

Calomel, when recently prepared, is per-fectly white and tasteless, but if kept sometime it acquires a buff colour, which, how-ever, is not of any importance, as far as its

efficacy is concerned, provided always, thatit be in very fine powder. Its specific gravityis 7.2; it is insoluble in water, and not poi-sonous, to use the term in its common ac-ceptation. With regard to its composition,that is evident, from the statement whichhas been made ; it is composed of one pro-portional metal 200, and one proportionalchlorine 36, giving 236 as its equivalent, orrepresentative number.Now in this preparation you have taken

the protosulphate of mercury, and commonsalt, and triturated them together, and theconsequence was the production of the proto-chloride of mercury ; but if you substitute forthe protosulphate, the persulphate, or oxy-sulphate of mercury, you will then obtainthe perchloride of mercury, or corrosive subli-mate. You take two proportionals of com-mon salt, or 120 parts by weight, and oneproportional of the oxysulphate of mercury-296, to produce 272 parts of corrosive sub-limate, so that mutatis mutandis, the theoryof the formation is the same. It may beobtained by applying chlorine directly to themetal with heat, as you see here. [Theexperiment was made, and a considerablequantity of corrosive sublimate obtained inthe retort.] This substance is of a brilliantwhite appearance when recently made ; itstaste is nauseously acid and exceedinglypoisonous : it dissolves in twenty parts ofwater at 60°, and in its own weight of boilingwater; but chemical authors differ on this

point. It is soluble in muriatic acid, but de-composable by alkalies and many other me-tals ; potash, soda, and lime, readily de-compose it.

It may be worth while to call your atten-tion to the decomposition of these two sub-stances, calomel and cormsive sublimate; in

order to explain to you the manner in whichthe decomposition actually takes place, toshow you its difrerence from the manner in

* which it was formerly supposed to take ptace.Before the discovery of chlorine, it wasimagined that calomel was a combination ofmuriatic acid and black oxide of mercury,and that corrosive sublimate was a combina-’ tion of muriatic acid with the red oxide, and! nothing seemed clearer than this. Now here

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in this glass is a solution of corrosive subli-mate, and in another vessel there is calomel.Potash, soda, or lime, maybe taken for theirdecomposition, and you observe that theone throws down a black powder, and theother a hydrated peroxide of mercury. Nowit has been said here, that the alkali takesaway the muriatic acid from the black oxide,and that in the other case it takes it from thered oxide, separating the oxides in their pureor free state. Now here are two tableswhich will show you the real explanation ofthis decomposition. Here we have calomeland potash acting upon each other, and theproduce is black oxide of mercury, that is tosay, the mercury of the calomel combineswith the oxyg’en of the potash, forming ablack or protoxide of mercury, and tle chlo-rine of the calomel combines with the potas-sium to form a chloride ofcotassium.

Now of the triple saitsof mercury; thertis a triple salt of ammonia and mercury,which is to be obtained by mixing a solutionof corrosive sublimate with a solution ojsal ammoniac, and precipitating the mixtureby potash ; a white powder falls down, whichis called a white precipitate, and in the Plar-macopoeia hydrargyrum precipitatum album, al-though, in fact, it is a triple salt, a muriate ofammonia, and mercury; it is used in medi.cine as an external application. These twochlorides of mercury are important, medical-ly speaking, and you will recollect, that inthe protochloride, or calomel, the mercury iscombined with one proportional of metal aDdone of chlorine, and in the perchloride or

corrosive sublimate, with one proportion ofmetal and two of chlorine ; and that youmay convert the corrosive sublimate intocalomel, by adding to it an additional quan-titv of mercurv.

lodii2e and mercury combine, and form aproto and periodide of mercury. The peri-odide of mercury assumes a beautiful redcolour, and it has been proposed to use it asa paint, but, like the other iodides, it isunfit for this purpose, since it does not re-tain its colour. ’1 hey are compounds of oneproportional and one, and of one and two, sothat their equivalents are 325 and 450.. Respecting the action of acids upon mer-cury generally ; it you boil mercury in sul-

phuric or nitric acids, but take the nitricespecially; if you boil mercury in excess ofnitric acid, the mercury becomes peroxi-dised, and you get a dense solution of per-oxide of mercury in nitric acid, forming a

pernitrate of mercury ; but if you take a largequantity of mercury, and a small quantity ofacid, and allow them to act slowly upon eachether, when cold, you get a solution of theprotoxide in nitric acid, or, in other words,a protonitrate of mercury; and you may judgeof the state of oxidisement of the solutions,by adding potash or soda, which gives a

grey precipitate in the first case, and a redprecipitate in the other. You find somechemists not content with two oxides of

mercury, but describing a half dozen moreand the fact is, that if you choose tomtitxtwo, you will get an indefinite number ofoxides. These are of no great importance,excepting as entering into combinatior withother preparations. The pernitrate is Jf afine red colour, and requires some nieftr inits preparation ; it generally retains sometraces of nitric acid, which it is difficult to

get rid of entirely. It is exceedingly caustic,and is used as a stimulating application tosores.

Sulphur and mercmy combine, and pro.duce a black or a persulphuret, and a red, ora protosulphuret of mercury.

With regard to the protosrelphuret, this haslong been known in medicine under ths

name of Æthiop’s mineral; it may be readily, obtained, by passing a stream of sulphu-! retted hydrogen through a solution of dilutenitrate of mercury. The persulphuret, or cin-nahar, is found native, and is one of thesources from which the mercury is ob.tained. It is used in the arts by the manu.facturers of good sealing wax, to give it thered colour ; the common colouring is redlead ; and the consequence is, that it turnsbrown or black when heated. Sulpburicacid and mercury form, when boiled to.

gether, a persul.phute of niercitry, and bytriturating it with mercury, it becomes con.verted into a protosulphate. fVlzen the per.sulphate of mercury is put into warm water,it is divided into two parts ; the one part isheld in solution, which is a bipensulphate, andthe other falls down in a yellow powder, andis a subpersulphate this I mention to you,as it is one of the preparations ot mercury,

which used formerly to be called turpethmineral, and it is only within a few years, thatthe list of minerals has been properlydiminished; formerly, they abounded to a

dangerous extent. It is violently emetic andpurgative, notwithstanding it was called bythe mild name of the mercurial alterative.It may be obtained, by pouring some waterupon the persulphate, and this sort of decomposition the salts of mercury are verysubject to, which throws considerable diffi-culty in the way of explaining them, andadds considerably to the intricacy of theirchemical history.The remaining combinations of mercury,

need not to detain more than a minute ortwo. Phosphorus unites with mercury, andforms a phosphuret; and a proto and per-phosphate are formed, by union with the

phosphoric acid. The phosphate of mer-cury became, at one time, a fashionable pre-paration, because some physicians said thatphosphoric acid was a favourite acid eiii-

ployed by nature in -the composition ofcer

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bodies: and they became very fond of givingphosphate of mcrucry, phosphate of soda,aud others, under the impressiou of phos-phoric acid being particulorty favourable to !the system, the absurdity of which I need not iadvert to. There is one salt still to advertto, which is the prussiate, or the cyanuret 0/ ’mercury; this is obtained by boiling thered oxide of mercury with prussian blue,filtering the solution, and then setting itaside to cool. On cooling, it deposits aquantity of white crystals, which are cyanuretof mercury, composed of one proportional ofmercury, and two proportionals of cyanogen ;so that 1 ought rather to have said, that itis a bicyanuret than a cyanuret. When this

cyanuret is heated, it is decomposed, eyano-gen is given out, and from this substanceGay Lussac obtained the singular gas, andhis investigations of which terminated inthe very important discovery of cyanogen.If you distil the cyanuret of mercury withmuriatic acid, you obtain a chloride of mer-cury, and a hydrocyauuret of mercury.There is an experiment, which once made

a great noise in the chemical world-naaiely, tlte metallisatiun of ammonia ; it wasimagined, that under certain circumstances,ammonia was capable of assuming the formof a metal ; ammonia, you know, is a com-pound of nitrogen and hydrogen ; and if truethat it could assume the metallic form, weshould have some insight into the compo-position of metals ; as it might then be said,that they were either compounds of nitro-Igen and hydrogen, or oxides cf these bodies.The experiment was made by electrifying aglobule of mercury upon a piece of sal am-moniac, or by pouring an amalgam of potas-sium and mercury upon apiece of sal am-moniac, and rubbing the mass with a littlesolution of ammonia. You will .observewhat will happen; the ammonia loses itsfluidity, puffs up, assumes the consistenceof butter, and appears to take on the crystal..lilie character. Now it appears, from recentexperiments, that this is nothing more thanmercury mechanically mixed with ammo-nia, that they are puffed up together, form-ing a sort of soap-suds of ammonia and mer.cury, and that there is no further approachto metallisation on the part of the ammonia.If you collect this substance and heat it,the ammonia flies off, and the mercury reoassumes its hquid form.

In the next lecture, we shall proceed tothe consideration of the metals silver andgold.

FOREIGN DEPARTMENT.

ON THE LATERAL DEPRESSION OF THE PA-RIETES OF THE CHEST.

BY BARON DUPUYTREN.

(Report. d’Anatomie, Tom. v., p. 198.)I PUBLISHED, ill one of the preceding

Numbers of the Repertoire,* a species of dis-placement of the femur, which is congenital,and which, t believe, has never been de-scribed by any other surgeon. t I am now

going to describe a deformity of the chest,still more common and important than theother malformation ; in fact, scarcely a

month elapses without several instances ofit coming under my notice. This deformityconsists in a depression of the sides of thechest, a proportional projection of the ster-num and abdomen anteriorly, and the ver-tebral column posteriorly. In children ofscrofulous and other cachectic constitutions,affected with this deformity, the sternum

projects like a keel ; the vertebral columnpresents quite a bump, whilst the sides arenot only flattened, but depressed. This dè-

formity exists to such a degree, sometimes,that the two sides of the chest may be em.braced with the fingers of one hand. Thetransverse diameter of the chest is thus

considerably diminished, whilst the antero-posterior is enlarged. The function of theorgans contained in the chest become im-

* Vide TnE LANCET, Vol. xi., p. 441.t I have been astonished on re-perusing

the paper, in which this kind of dislocationis mentioned, to observe the indication ofone fact overlooked, viz., that the congeni-tal dislocation of the femur, which, in thegreater number of cases, exists on both sidesat one time, is found, in some individuals,on one side only. Among the twenty casesof this disease which I observed, the dislo-cation existed on one side only in two orthree individuals. I have, at this moment,before me, a young child with congenitaldislocation on the right side only, and whatrenders the case still more interesting is,

that the child has a sister affected with thesame disease on the right side. I will avail

myself of this opportunity of remarking,that since the publication of the paper onCongenital Dislocation of the Femur, I haveseen five or six other instances of this mal-formation. I saw one with Dr. Louyer Vil-lermay, where the exquisite pain liointedout to our notice the seat of the mischief.. _.