OP ARTS AND SCIENCES. 41 



If in calculating the per cent of chlorine from the results of the 

 above determinations we use the atomic weights for silver and chlorine 

 obtained by Stas (namely, CI = 35.457 and Ag = 107.93), these per 

 cents will be in each case very nearly 0.020 lower, and we shall obtain 

 for the mean value 46.600 instead of 46.620. Moreover, on this 

 assumption the atomic weight of antimony, deduced from Dumas's an- 

 alysis of the chloride, would be 121.95 instead of 122. Again, if we use 

 Stas's value of the atomic weight of sulphur (S = 32.074) in calculating 

 the atomic weight of antimony from our own results, on the synthesis 

 of the sulphide, we should obtain 120.28 instead of 120; and, lastly, 

 the values Sb = 120.28 and CI = 35.457 give for the per cent of 

 chlorine in antimonious chloride the value 46.931. 



Here, then, is a most striking result; for these determinations con- 

 firm the value of the atomic weight of antimony obtained by Dumas 

 as closely as did the previous determinations confirm that obtained by 

 Schneider. Evidently, there was a large constant eri'or in one case or 

 the other. Moreover, it appeared improbable that in either case any 

 error could arise in the chemical process employed : for, in the first 

 instance, we had a synthesis by one method confirming an analysis by 

 a wholly difierent method ; and, in the second instance, the analytical 

 process employed is regarded as one of the most accurate known to 

 science, and we had apparently shown that its accuracy was not impaired 

 under the peculiar conditions present. It appeared, therefore, reasonable 

 to assume that the results did truly indicate both the actual proportion 

 of antimony in the sulphide of antimony and of chlorine in the chloride 

 of antimony analyzed, and to look for the cause of the discrepancy to 

 some impurity in one or the other compound. We therefore next 

 sought to determine how much sulphide of antimony could be obtained 

 from a given weight of chloride of antimony, hoping that by thus 

 bringing the relations of antimony to chlorine and sulphur into close 

 comparison the source of the error might be indicated. 



The precipitation of sulphide of antimony from a solution of the 

 chloride in tartaric acid is made under conditions which are far more 

 favorable to accurate results than those with which we were obliged to 

 contend in our previous experiments. If the solution is diluted with 

 water charged with carbonic dioxide, and if the precipitation is made in 

 the way we have described,* we can avoid all excess of hydrochloric 

 acid except that which is formed by the chemical reaction, and there 

 is then no oxichloride of antimony formed, and no subsequent loss 



* See page 14. 



