0-N Tl^'. 43 



F;u'ts and ob»> 

 Sulphur et and Potash. nervations on 



,.., ,, ., . 11 ^r- till and its com- 



Liquid potash has not the least action upon siu|)liuret ot tin; py^,j,ds. 



that of antimony is affected quite otherwise under similiw cir- 



xjamstanccs. Antimony, however, is^far from possessing so 



great an aftiiiity to oxigen as tin does. I'liis diversity shews 



?iow cautious we ought to be in forming previous judgments in • 



chcmistiy. 



Mosaic Gold and Poiash. 



Liquid potash, assisted by heat, dissolves mosaic gold. The 

 changes it undergoes are curious. As they tend to throw a 

 light on the theory of oxidation, it may be useful to detail 

 them; but to do this with clearness, it is indispensable, first, 

 to speak of the hydro-sulphurets of tin, combinations which 

 I have hitherto but imperfectly understood, and of which 

 the denomination will stand in need of being improved. 



Major Hydro-Sulphnrct of Tin. 



A current of sulphurated hydrogen is passed through any solu- 

 tion, of which the oxide is perfectly at ti maximum ; and a yellow 

 jMecipitate will be obtained, to be collected, washed, and left to 

 dry. To obtain more precipitate, it is proper to saturate the 

 excess of acid in the solution; for when that predominates too 

 much, thf! hydrogen with more difficulty attracts the oxide. 



The precipitate possesses the following characters : Heated 

 with marine acid, it dissolves with effervescence, yields abun- 

 dance of sulphurated hydrogen, and is reduced to a simple 

 muriatic solution, in which the oxide is always found at a 

 maximum. This clear yellow precipitate, so long as it remains 

 clear, is what we call hjdro-sulphurct major ; it augments the 

 number of those combinations, which serve, in chemistry, to 

 demonstrate the facility with which mere heat can vary th« 

 affinities. At an ordinary temperature, sulpluirated hydrogen 

 is an acid which takes the oxide from muriatic acid : but at 

 the temperature of boiling water, the latter, in its turn, acts 

 upon the sulphurated'hydrogen, and resumes its oxide of tin. 



Dry hych'o-sulphuret of tin is of a dark-brown colour : it is 

 vitreous in the fracture of its pieces, as are likewise the oxide 

 major, the purple of cassius, and the native oxide. Potash 

 readily dissolves it, and acids precipitate it without alteration. 



G2 K 



