TIN

TIN

( 425 )

cf calomel arifmg from the partial decompo-fition of the corrofive muriat, and if the heathas been kept at rednefs for a fufficient time,all the muriated fub-oxyd of tin, calomel, andrunning mercury, will be fublimed, and onlya grey powder left, which is probably chieflya fub-oxyd of tin.

The fmoking muriat when inclofed in a bottleprefents nothing remarkable, but the empty partof the bottle above the level of the liquid foonbecomes lined with cryftailine needles, whichgenerally caufe the hopper to adhere to a verytroublefome degree. When this liquor is ex-pofed to the air it immediately fends forth aquantity of denfe white vapours which excitecoughing, and condenfe into a femi-cryftallizedpellicle on the contiguous furfaces. The pre-cife nature of this Angular liquid has been il-luftrated by a very ingenious fcries of experi-ments by M. Adet, m and afterwards by M.Pelletier. 11

From thofe of the former chemift we have thefollowing fa£ts : when a little of this liquor ispoured into a cup, and enclofed under a bell-glafsover water, the whole of it evaporates in whitefumes, which prefently cryftallize on the fidesof the glafs in the form of a faline vegetation.Thefe cryftals have now loft the property offmoking, are fomewhat deliquefcent, and readi-ly difl’olve in water into an acid folution ofmuriat of tin. This cryftallized condenfationof the vapour is owing to its union with themoifture held in folution in the air, and whichis conftantiy fupplied by the water over whichthe veflel Hands, fo that in fact this fubftanceis a moil powerful hygrometer. In proof ofwhich M. Adet found, that when the fumingmuriat was confined with a fmall quantity ofdry air, fcarcely any of the cryftalline vegeta-tion was depofited, but it immediately appearedwhen the air from the lungs was introduced,which is known to be loaded with moifture.The fmoking muriat therefore lofes its fmokingproperty, and iolidifies by union with a certainquantity of water, and is again reducible to aliquid by a greater proportion of water. Thismay alfo be fliewn more diredlly; when the mu-riat is mixed with not more than about a third ofits weight of water, much heat is given out,and the whole fuddenly congeals, at a commontemperature. At the fame time a number ofbubbles of gas, apparently pretty pure azot, aregiven out, the caufe of which is not very ob-vious, but it feems to bear an analogy with theexpuliion of air from water, and all other li-m An. Ch im. tom. i.

quids in the act of freezing; and botn in thiscircumftance, as well as in the evolution of calo-ric, the fixation of the water may be confideredas equivalent to congelation. This folid mafsreadily liquefies in a gentle warmth, and by theaddition of more water it is refolved into a merefolution of the fuperoxydafed muriat of tin with-out giving out any more vapours.

The habitudes of. this muriat with regulinetin throw much light upon its true nature. Ifthis muriat, diluted with fo much water as tobecome folid when cold, is liquefied by heatand digefted with fome filings of tin, a con-fiderabie portion of the frelli metal is diffolved,without the difengagement of hydrogen or any gaswhatever, and when faturated, the folution liasnow loft all the charabteriftic properties of thefmoking muriat, will bear being heated to red-nefs with very little lofs by fublimation, andthen concretes into a brown mafs which ciofeiyrefembles the common fufed muriated fub-oxyd.This linking experiment (hews, in the firftplace, that the tin in the fmoking muriat is in ahigh Hate of oxydation, fo that it can impart aportion of oxygen to an additional quantity ofmetal fufficient for its folution ; for as no hy-drogen is given out, the oxygenation of thefreffi portion of metal cannot (as in the com-mon folution in the muriatic acid) arife fromthe decompofition of water. It alfo fhews thattin in a low ftate of oxydation requires much ieismuriatic acid for its folution than in the higherftate, (and confequentiy that its affinity for theacid is ftronger) otherwife the tin bit added,though oxydated, could not be held in folution,as it is, and with that fenfible excefs of acidwhich, as we have already mentioned, is efien-tial to a folution of the muriated fub-oxyd.

Pelletier in his experiments on muriat of tin(many of which have been already related) en-deavoured to form the fmoking muriat by com-pleatly oxygenating the common folution of tinin muriatic acid. This he effebted by pallingoxymuriatic gas through this folution, which ab-forbs it readily, 2400 grs. of tin diffolved in fourtimes its weight of common muriatic acidtaking up 2 oz. of the gas. This liquid, boiledfor a few minutes to expel a little uncom-bined gas which it contained, yielded a clearlimpid folution, free from the peculiar pungentfmell of oxymuriatic acid, in which the metalis certainly as highly oxygenated as poluble.When this folution was evaporated confiderablyit depofited cryftals exactly refembiing thofeafforded by the fmoking muriat when a little

» Meuioires d« Pelletier, tom. I.

3 H

YOL. II.