[ 69 J 



XIII. On the Oxides of Gold, Tin, and athe?- Metals; with 

 Hints for extending their Uses in Dijein'j;. Communicated 

 in a Letter to M. Berthollkt Ly M. John JNIiciiael 

 Haussman*. 



jL believe that I am as well founded as yourself" Tn admit- 

 ting of intermediate terms of oxidation between the mininjimi 

 and maximum of several metallic substances. I shall, bv- 

 and-by, cite an example of the oxide of tin at the minimum 

 precipitated from its muriatic solution, and redissolved by an 

 excess of caustic potash; the alkaline metallic solution of 

 which I have already mentioned in mv observations upon 

 the Adrianople red, inserted in the Annules de Chimief, as 

 well as in another memoir upon the coloured oxides of tin, 

 given to the public in the Journal de PJiysiqm. In avoid- 

 ing to dilute the muriatic solution of tin too much with 

 water, and employing a solution of caustic pota?h very much 

 concentrated, a considerable quantity of caloric disengages 

 itself during the mixture of these two liquors : one portion 

 of the tin precipitates itself in the metallic state, while the 

 other remains in solution in a state of intermediate oxida- 

 tion. This alkaline solution has so strong an aflinitv for 

 oxygen, that it changes into a gray colour the yellow oxide 

 of gold fixed upon a piece of cotton bv means of ammonia, 

 while a similar yellow piece does not change its colour when 

 allowed to soak in a pure liquor of caustic potash, Th€ 

 same change takes place upon plunging a small piece of 

 cotton, which had been saturated with a solution of gold, 

 well squeezed and dried, into an alkaline solution of tin. 

 The same cftect will follow if we pour into this alkaline so- 

 lution a solution of gold diluted with water. 



The change of the yellow colour of the oxide of gold by 

 the alkaline solution of tin is not the only proof of the in- 

 termediate oxidation : this liquor, besides, possesses the pro- 

 perty of extracting the blackish brown colour of the oxide of 

 jpanganese fixed upon a piece of cotton by an alkaline pre- 



I 



• From the /l.-mu.'cs dc Chin- it, JIo. 1C6. 

 I Sfi> Phil. M^5. v<;l. nii. and vol. xviii, 



K 3 /Ipitate. 



