OF ARTS AND SCIENCES. 13 



behind on evaporation a sufficient amount of oxicbloride to reduce the 

 per cent of chlorine 0.1 IG (loc. cit. page 64). The mean results 

 which we actually obtained from seventeen analyses of chloride of 

 antimony was 4G.G20 ; and when to this we add 0.212 and O.llG, the 

 sura is 46.948, which differs from 46.985 — the theoretical value 

 when Sb = 120, and CI =35.457 — by only 0.037, or if we take 

 CI = 35.5 by 0.072. In this estimate we leave out of the account 

 the known solvent action on chloride of silver of the tartaric acid 

 used to keep the antimony in solution. This must equally affect 

 botli of the series of determinations given above, and fully accounts 

 for the small difference that remains to be explained. This whole 

 discussion, however, only serves to confirm the conclusion previously 

 expressed, that chloride of antimony is a most unsuitable material 

 for the basis of an atomic weight determination ; and, having ex- 

 plained the anomaly to which we gave prominence in a previous 

 paper, we shall here take leave of the subject. We have also studied 

 the solubility of bromide of silver in water, but this is so small that 

 we found it difficult to measure the amount. In water at the ordinary 

 temperature, or even in tepid water, bromide of silver is practically 

 insoluble. In boiling water it is perceptibly soluble, but not more so 

 than is chloride of silver in water at the ordinary temperature. Hence 

 the determination of bromine does not require the same precautions, 

 and is susceptible of greater accuracy than that of chlorine ; and on 

 this account, as well as for other reasons which we have previously 

 discussed, the atomic weight of antimony can be deduced from the 

 analyses of the bromide of antimony with as great accuracy as can at 

 present be reached in such determinations. In the seven determina- 

 tions of the per cent of bromine in bromide of antimony, whose results 

 are given beyond (p. 18), the maximum difference from the mean value 

 66.6651 was only 0.0045, and Professor Mallet, in his analyses of 

 bromide of aluminum, has obtained with the same method a similar 

 degree of accuracy.* 



In conclusion, we would again express our obligations to Mr. G. M. 

 Hyaras, who has assisted us in the work of this investigation. 



IV. Additional Experiments on the Atomic "Weight op 

 Antimony. 



In our previous j^aper on this subject, we gave our reasons for the 

 opinion, since fully confirmed, that the bromide of antimony is the 



* Philosophical Transactions, Part III. 1880, 1022. 



