OXIDATION, 



xviir. 



265 



Extras of a Letter from M. John Michael Haussmann, 

 to M. Berthollet, on the Exijience of intermediate Terms 

 of Oxidation. * 



1 THINK there are fufficient grounds for admitting, with ^^'^fn" of ir 

 you, that there exift, in the oxidation of many metallic bodies, degrees of^jjii^j^ 

 intermediate degrees between the minimum and the maximum. t'°n of metals. 



The firft example I (hall cite, is, that of a mm.mum oxide Oxide of tin. 

 of tin, precipitated from the muriatic folution, and diflfolved 

 in an excefs of cauftic potafh ; a metallic alkaline folution 

 M'hich I have before noticed in my Obfervations on the Red 

 Dye of Adrianople, inferted in the " Annates dc Chimie," and 

 alfo in a Memoir on the coloured Oxides of Tin, inferted in the 

 " Journal de Phi/fique." 



By avoiding any dilution of the muriate of tin, and ufing Expetlmcnt. 

 a very concentrated folution of cauftic potafti, the mixture /^.""^''^°^ '^'" 



• r ... 's in part prc- 



difengages much caloric, part of the tin is precipitated in thecipitated metallic 

 metalline ftate, whilft the remainder is held in folution in^n ^'^^ ^^^ '^^^ , 

 intermediate ftate of oxidation. This alkaline folution is fo intermediate' 

 difoxidant, that it changes the yellow oxide of gold, fixed on oxidation, 

 icotton, by means of ammonia, to a grey ; whilft a firailar 

 yellow pattern underwent no change of colour on 'being 

 Jlleeped in the iimple liquor of cauftic potafli. A like altera- 

 tion took place on dipping a cotton clolh, which had been 

 previoufly liained with the folution of gold, and well dried 

 in the alkaline folution of tin, which alfo produced the fame 

 effefl on pouring into it the pure folution of gold diluted 

 with water. 



This change of the yellow colour of oxide of gold by the Other proofs of 

 alkaline folution of tin, is not the only proof of an interrae- ^j." j^'"J^"^ '* 

 diate ftate of oxidation ; this liquor poflefTes befules, a pro- 

 perty of deftroying the blackifti-brown colour of the oxide of 

 raanganefe ftained upon cotton by an alkaline precipitant. 



All thefe changes are more rapidly produced, if, prior to the 

 precipitation and folution in the cauftic potafti liquor, the 

 muriatic folution of tin be diluted with (ix or eight parts of 

 jyater, in which cafe there i« no fenftble difengagement of 



* Annales de Chimie, Vol. LVI. 5. 



caloric 



