PROCEEDINGS OF THE AMERICAN ACADEMY 



is obviously therefore no danger of the formation of this j^rotluct in 

 the precipitation of chlorine, bromine, or iodine from solutions of the 

 antimony compounds of these elements in tartaric acid, unless the 

 excess of silver nitrate is very large and the solutions very concen- 

 trated ; and although we have most carefully looked for it in the 

 precipitate we have never discovered it, except under the peculiar 

 conditions described in our former paper, and our fear that it might be 

 occluded by these precipitates was wholly unfounded. 



It is evident from the above experiments that the solubility of silver 

 emetic in water like that of cream of tartar and other salts of tartaric 

 acid is very greatly increased by heat, and we were easily able to 

 obtain good crystals of the compound in large quantities by dissolving 

 the precipitate, obtained as Wallquist describes, in boiling water, and 

 allowing the solution to cool. The crystals are colorless and have a 

 very brilliant, almost an adamantine, lustre. 



From the reaction by which silver emetic is formed we should infer 

 that the composition of the salt would be expressed by the symbol 



Ag, SbO,H,^OXC,HA)-H,0. 



This compound would theoretically contain 2G.34 per cent of silver 

 and, as a mean of tJn'ee analyses, we obtained for the amount of silver 

 in the crystals 26.30 per cent, as previously stated. 



The crystals of silver emetic rapidly blacken in the light, and are 

 very easily decomposed by heat. This decomposition takes place at 

 about 200° C. with a slight explosion. A very 

 fine carbon dust is blown out of the crucible, 

 and a residue is left behind, which under the 

 microscope is seen to consist of spangles of 

 metallic silver mixed with an amorphous 

 powder. Almost the whole of the powder 

 dissolved easily in a solution of tartaric acid, 

 and it evidently consisted of SbgOg. In one 

 experiment we weighed the silver emetic and 

 the product, and found that 0.8460 gramme of 

 the salt left 0.5304 gramme of residue. If the 

 residue consisted solely of silver and Sb^Og, 

 theory would require 0.5200 gramme, and it can be seen from this 

 how perfect the decomposition was. It is obvious, therefore, that were 

 this compound occluded as we at first feared, it would have made itself 

 evident on drying the precipitates. 



Mr. W. II. Melville, assistant in this laboratory, has made the fol- 



