TIN

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TIN

C

430

jjliuret of tin is obtained. To faturate the tinwith fulphur the heat fhould be moderate, andthe projedtion of fulphur repeated once or twice,till the tin appears to be faturated.

The quantity of fulphur retained by the tinin this procefs is varioufly given, and no doubtactually varies. Mr. Woulfe s found 4 oz. oftin to furnifh 5 oz. of the fu'phuret, and eventhen it is not entirely faturated, for on rubbingit in a mortar a portion remains which extendsunder the peftle, and therefore is Hill malleableand unfaturated with fmpliur.

On the other hand, Bergman finds that 100parts of tin will take up in this way no more.than 20 of fulphur, in which proportions Proud;.agrees. But Pelletier f found the increafe ontoo of tin to be no more than 16J of fulphur,fo that the faturating proportions of fulphurand tin are ftill unknown, and could only bedetermined with accuracy by adding an excefsof fulphur to the pulverized fulphuret made inthe way above mentioned, and keeping the mafsjuft at fufion in a clofe retort as long as anylulphur fublimed from it.

This fulphuret is a black brittle fhining fub-ftance, of a flaky confiftence, and clofely re-fembling molybdena in appearance. Whenmelted and cooled very flowly it aflumes a la-mellar texture, in the hollows of which arefeen dillinft needled and fometimes cubic cryf-tals.

This fulphuret is not added on by a folutionof cauftic potafh. u When digclted with nitricacid a large quantity of nitrous gas is given out,from which, and from the analogy with the otherfulphurets made by fufion, we may concludethe metal to be in the reguline {fate in this com-pound.

Vfhcn a current of fulphuretted hydrogen-gasis palled through any folution of fuper-oxydatedtin, T a vellow precipitate of hydro-fulphurettedfu-peroxyd gradually colledfs,which takes place withmore eaie if a little alkali is previoufly added tothe folution till the moment that a precipitatebegins to appear. When the hydto-fulphuretis heated with muriatic acid it again quits theoxyd of tin with effervefcence, and refigns it tothis acid. Hence it appears that the affinity offulphuretted hydrogen for this oxyd of tin isgreater than that of muriatic acid in a low tem-perature, but lefs, when the heat is raifed.When this yellow hvdro-fufphurct is dried itbecomes vitreous in its fradfure, it is eafily fa-llible in potalh, and precipitated thence by acidsunaltered. When gradually heated per fe, wa-* r’lil. Tram ', vel. (,l. ' Memoires, vol. ;

ter, fulphureous acid, and fome fulphur aregiven out, and the refidue, if not overheated, isthe golden fulphuretted oxyd of tin, or AurumMufivum, which will be preiently deferibed atlarge. The affinities that adf in this procefsare complicated. They are ffated by Proult tobe the following : the oxyd of tin gives out partof its oxygen, of which one portion unites tothe hydrogen of the hydro-fulphuret, and formswater, and the remainder carries off with itpart of the fulphur as fulphureous acid; fomeexcefs of fulphur beyond the requilite propor-tions for the aurum mufivum is all'o volatized ;whilft the remainder of tM fulphur, and the tin,now in low oxydation, unite into the aurummufivum which remains behind.

When fulphuretted hydrogen gas is palledthrough a folution of fub-oxydated tin, fuch asthe common muriat recently made, a dark cof-fee-coloured precipitate takes place, which isthe hydro-fulphurcttedfub-oxyd , and when yvafhedwith boiling water it dries of the fame co-lour.

This hydro-fulphuret is alfo decompofed bymuriatic acid with effervefcence in a boilingheat, but it gives no aurum 'mufivum whenheated per fe. When heated with a foiution ofcauftic potafh, both a folution and precipitationtake place; the precipitate is the fimple ful-phuret with the tin in the metallic hate; thefolution on the other hand, is a hydro-fulphuretof potafh holding the metal in the higheft (fateof oxydation, fince acids precipitate the hydro-fulphuret yellow, like that firfl deferibed. Thepotafh therefore caufes the condenfation of allthe oxygen into a portion of the fubftance, to-gether with all the hydrogen, at the expence ofthe other , portion, which is then found defti-tute of both. This effe£t of potafh, in con-centrating all the oxygen into that portionwhich it diffolves, is analogous to what occursin other cafes, and depends on the much greateraffinity of the fuper-oxyd than of the fub-oxydfor this alkali. A fimilar a£fion takes placewhen the fub-oxyd of tin, fulphur and folutionof potafh arc heated together, and p hy.dro-ful-pliuret of fuper-oxydated tin is produced. Inlike manner if liquid muriated fub-oxyd of tinis poured into liquid fulphuret of potafh, a yel-low precipitate takes place, which is the fuper-oxydated hydro-fulphuret.

A beautiful golden-coloured fpecies of ful-phuret of tin has long been known in the arts,under the name of Aurum Mufivum , or Mafai-cum, (Mofaic Gold). It is in the form of a, " i*rouft Phyf. tom 61. T Ibid,