$t6 OnthtOxyiaiionofTtn,^i:. 



atic acid, jJarticiilatly wlien the tin contains arfenic, which may be very Well afcertained, {ly 

 turning the gas under a glafs veflel, when the arfenic is depofited on the fides. Prouft alfo 

 obferves, that this gas is very hurtful to the brlghtnefs of the purple of powder of, caflius- 

 He therefore very properly advifes, that the folution fliould be heated before it is ufed: an 

 obfervation of the greateft importance for porcelain and enamel painters. 



If a few drops of the moriate of tin, be added to the muriatic acid of commerce, the 

 yellow colour of the latter inftantly difappears. The tin deprives the iron of the excefs of 

 oxygen, which rendered it red, and ammoniac then precipitates it of a green colour. The fame 

 thing happens with the folutions of the fulphates, nitrates, and red muriates of iron. 



But, if a ftroriger dofe of muriate of tin be poured into the muriatic acid of commerce, a 

 grey powder falls down, which Prouft has afcertained to be mercury. 



When a folution of the muriate of tin is diftilled, the whole of the liquid comes over, with 

 a portion of the muriate. Towards the end, the matter fwells up, and afterwards f:ttles in the 

 flate of calm fufion, of a green colour; and if the fire be raifcdj pufFs of fuming vapour are 

 driven ofF, but nothing comes oVer in the fluid form. If the muriate of tin contains a fmalf 

 portion of fulphuric acid, that acid is decompofcd, and the fulphur partly unites with the tin, 

 forming a fulphuret, in vi'hich the tin is oxyded to the minimum. This muriate requires a 

 ftronger heat for its diftillation, than the fmoking muriate irt the ordinary procefs. 



But that fubftance which rifes, and is condenfed in the neck of the retorts, proves, after 

 wafiiing, and feparating the fuming muriatcj to be nothing but tin half oxyded, to which acid 

 only need be added, in order to diflblve it again. This diftilled muriate eiFeftually decompofes 

 the fublimate of mercury, and all the mercurial preparations, or oxydes; while the fuming 

 muriate, being oxyded to the maximum, dccompofes nothing. 



The muriate of tin affords, with alcalis, a precipitate, which cauftic pot^afli abundantly dif- 

 folves. This folution referved, in a clofe vefl'el, at the end of 1 2 or 15 days, affords a metallic 

 group, in the form of cauliflowers, which confifts of tin, nearly pure^ In this procefs, one 

 part of the tin, oxyded to the mininum, robs the other, and becomes falurated; and this mu- 

 riate of tin, fo faturated, is no longer capable of altering corrofive fublimate. 



The fame thing happens, if a mixture of the carbonate of copper, and the oxyde of tin, fe- 

 parated fromithe muriate by pot-afh, be kept under water. The oxyde of tin robs all the 

 copper of its oxygen, aiid the portion of carbonic acid; whence the copper is found reduced, 

 in cryftalized plates, among the oxyde of tin. 



Laftly, the muriate of tin difoxygenates indigo, and changes it to grcert. This experiment 

 is analogous to other difoxygenations of the fame fecula, known to dyers. ProUft mentions 

 <his circumftance as an obje(Sl deferring of great attention, upon which he means to malce 

 -further refearches. 



The fulphates, nitrated, muriates, acetates, and carbonates, of copper, and alfo, the red, 

 blue, or green oxydes, mixed vvith the muriate of tin, are generally converted into a white 

 oxyde, which is collefted at the bottom of the vefTel; and if this muriate be palTed again upon 

 a new oxyde, it becomes itfelf green, and is faturnted to fuch a degree as no longer to 

 alter the colour of oxydes. The powder, thus robbedliy the muriate of tin, afTumes differ- 

 ent fhades of colours, violet, blue, black, &c. which are more particularly governed by the 

 - , degree 



