]28 COMBINATIONS OF OXIMUKIikTIC ACID AND METALS* 



chlorine, it is only necessary to compare them with the ana- 

 lyses of the oxides of the same metals. If the two agree, 

 there will be reason to consider them both correct, but should 

 they disagree, there is equal reason for supposing one or both of 

 them to be wrong. 

 Applied to the Thus as the orange oxide'of copper is analogous to cuprane, 

 compounds of g^d the brown oxide to cupranea, the oxigen and chlorine 

 ' should be to each other in these compounds as T'b to 33'6. 



And from comparison of my analysis with those of Mr. Che- 

 NEvix and Mr. Pkoust, it appears, that in the two first; 

 copper being as 60, the oxigen is to the chlorine as; ^'']Q, 

 instead of ^^'5 to 33'77j instead of 336 j and in the two last 

 as T'6 to 33'6, or as 15 to 672. Coincidences as near as might 

 be reasonably expected, 

 ^fjj,^. There is not the same agreement between Mr. Proust's 



analyses of the oxides of tin and the preceding ones of the 

 combinations of this metal and chlorine. This discordance 

 induced me to repeat my analyses j and, obtaining the same 

 result as at first, I directed my attention to the oxides of tin, 

 and made the following experiments to ascertain the propor- 

 tion of their constituent parts. 

 . 42'5 grains of tin, which had been precipitated from the 



on the oxides muriate of this metal by zinc, were heated with nitric acid in a 

 •ftin.) platina crucible, and slowly converted into peroxide; the acid 



and water were driven off by gentle evaporation at first, and 

 afterward by a streng red heat, continued for a quarter of an 

 hour. The peroxide thus produced was of a light yellow 

 colour, and being very gradually dried, it was semitranspa- 

 rent, and hard enough to scratch glass ; it weighed 54*25 grains. 

 Hence, as 42*5 grains of tin acquire, on conversion into per- 

 oxide, 1175 grains of oxigen, this oxide appears to contain 

 21'66 per cent of oxigen, just the quantity found in the 

 native oxide by Klaproth, instead of 28, the proportion stated 

 by Proust. 



Mr. Berthollet, jun,, has shown, that Mr. Proust's estimate 

 of 20 per cent of oxigen in the protoxide is incorrect. To 

 ascertain the true proportion, 20 grains of tin were dissolved 

 in strong muriatic acid in a retort connected with a pneumatic 

 apparatus, and without the assistance of heat j l6 cubic inches 

 of hidrogen gas were produced. (Barom. 30, thermom. 60.) 



As 



