ANTIMONY. 221 



be applied to the discussion of all these series further along. It may, 

 however, be properly noted at this point that the probable errors assigned 

 to the percentages of oxygen in three of Kessler's series are too low. 

 These percentages are calculated from the quantities of KC10 3 involved 

 in the several reactions, and their probable errors should be increased 

 with reference to the probable error of the molecular weight of that salt. 

 The necessary calculations would be more laborious than the importance 

 of the figures would warrant, and accordingly, in computing the final 

 general mean for antimony, Kessler's figures will receive somewhat higher 

 weight than they are legitimately entited to. 



Naturally, the concordant results of Dexter, Kessler, and Dumas led 

 to the general acceptance of the value of 122 for antimony as against the 

 lower figure, 120, of Schneider. Still, in 1871, linger * published the re- 

 sults of a single analysis of Schlippe's salt, Na 3 SbS 4 .9H 2 0. This analysis 

 gave Sb = 119.76. if S = 32 and Na = 23, but no great weight could be 

 attached to the determination. It served, nevertheless, to show that the 

 controversy over the atomic weight of antimony was not finally settled. 



More than ten years after the appearance of Kessler's second paper the 

 subject of the atomic weight of antimony was again taken up, this time 

 by Professor Cooke. His results appeared in the autumn of 1877 1 and 

 were conclusive in favor of the lower value, approximately 120. For full 

 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 antimony 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 compounds, tartaric acid was added,* and 

 then, with a supersaturated aqueous sulphhydric acid, antimony trisul- 

 phide was precipitated. The precipitate was collected by an ingenious 

 process of reverse filtration, converted into the black modification by 

 drying at 210, and weighed. After weighing, the Sb. 2 S 3 was dissolved 

 in hydrochloric acid, leaving a carbonaceous residue unacted upon. 

 This was carefully estimated 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 trisulphide was 

 weighed only in the red modification, and the results were uncorrected 

 by conversion into the black variety and estimation of the carbonaceous 

 residue. In fact, every such conversion and correction was preceded by 

 a weighing of the red modification of the Sb,S 3 . The mean result of these 

 weighings, if S 32, gave Sb = 119.994. The mean result of the cor- 



* Archiv. der Pharmacie, 197, 194. Quoted by Cooke. 

 f Proc. Amer. Acad., 5, 13. 



