196 THE ATOMIC WEIGHTS. 



details the original memoir must be consulted ; only a few 

 of the leading points can be cited here. 



Schneider analyzed a sulphide of antimony which was 

 already formed. Cooke, reversing the method, effected the 

 synthesis of this compound. Known weights of pure anti- 

 mony were dissolved in hydrochloric acid containing a little 

 nitric acid. In this solution weighed balls of antimony 

 were boiled until the liquid became colorless ; subsequently 

 the weight of metal lost by the balls was ascertained. To 

 the solution, which now contained only antimonious com- 

 pounds, tartaric acid was added, and then, with a supersat- 

 urated aqueous sulphhydric acid, antimony trisulphide was 

 precipitated. The precipitate was collected b}' an ingenious 

 process of reverse filtration, converted into the black modi- 

 fication by drying at 210°, and weighed. After weighing, 

 the SbjSg was dissolved in hydrochloric acid, leaving a car- 

 bonaceous residue unacted upon. This was carefully esti- 

 mated and corrected for. About two grammes of antimony 

 were taken in each experiment and thirteen syntheses were 

 performed. In two of these, however, the antimony tri- 

 sulphide was weighed only in the red modification, and the 

 results were uncorrected by conversion into the black va- 

 riety and estimation of the carbonaceous residue. In fact, 

 every such conversion and correction was preceded by a 

 weighing of the red modification of the SbjSg. The mean 

 result of these weighings, if S = 32, gave Sb = 119.994. 

 The mean result of the corrected syntheses gave Sb = 

 120.295. In these eleven experiments the following per- 

 centages of S in SbjSa were established: 



28.57 

 28.60 



28.57 

 28.43 

 28.42 

 28.53 

 28.50 

 28.49 

 28.58 

 28.50 

 28.51 



Mean, 28.5182, ±z .0120 



