Cryjlah of Oxidated Tin Ore. 159 



tals are fo Infoluble in acids, and combats the idea of Klap- 

 roth, that it arifes from fuperfaturation by oxygen, which is 

 diflipated by fluxing the orevrith vegetable alkali. 



" I believed I had good reafon," fays he, *'to doubt that 

 the complete oxygenation, or (if the term be preferred) the 

 fuperfaturation by oxygen, was the true caufe of its infolu- 

 biUty in the muriatic acid ; becaufe I could not, at any one 

 inftant of the operation, perceive either the fubftance that 

 fhould take it away, or any of the phenomena that w^ould 

 have accompanied its difengagement. That I might with tlie 

 greater facility obferve all the circumflances, I operated with 

 a fmall platina cinicible over an Argand's lamp. Fifty-five 

 centigrammes of brown cryftals of tin were reduced to a fine 

 powder, and mixed wath fix times as much pot-afti (purified 

 by alcohol, and dried) : the mixture was moiftened with a few 

 drops of water, I evaporated it firft to drynefs, and then to 

 a commencement of fufion. After the firft treatment, hot 

 .water poured on the mafs diflTolved more than half the mi- 

 neral, which was then firft precipitated from it by muriatic 

 acid, and afterwards redifl^olved by it with the greateft faci- 

 lity ; and the precipitate of the metallic oxyde, reproduced 

 by adding carbonat of pnt-afh, was found, as ftated by Klap- 

 roth, comp'etely folublc again by the fame acid. After hav- 

 ing my klfwitnefTed this faft, my firft doubt on the dire<St. 

 caufe of the infulubility of this ore was rather ftrengthened 

 than removed. It caimot be faid that the excefs of oxygen 

 efcaped during the fufion with the pot-afli ; for the metal 

 could not form a folublc combination with alkali, unlefs it 

 was oxidated in the higheft degree; or, more properly, in 

 the ftate of an acid, fo as that the folution filtered from the 

 fefidue fliould be a true ftannatc, or (if the term be pre- 

 ferred) ftannitc of tin*. 



" Now, if wc are obliged to admit that all the oxygen of 

 the ore is again found in the alkaline folution, it cannot be 

 the lofs of a fart of that principle that renders the metal 



' The auilioi muft liavc written Staiinicc of pot^alli. D. 



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