62 PEOCEEDINGS OP THE AMERICAN ACADEMY 



Reduction of Argentic Sulphide. 



Thied Series of Experiments, Temp, below Visible Redness. 



Tj.„ Wt. ofAgjS. Wt. ofS. At. Wt. ofS. At. Wt. ofS. 



■""• grammes. by loss. Ag = 108. Ag = 107.93. 



1. 1.1357 0.1465 31.990 31.969 



2. 1.2936 0.1670 32.010 31.990 



Mean value 32.000 31.980 



"We are sure that in these experiments no silver was lost, because 

 the least trace of sublimate would have been visible on the glass. We 

 cannot be so certain that a trace of sulphide did not remain unreduced ; 

 but we do feel confident that the true value of the atomic weight of 

 sulphur — so far, at least, as it can be determined by the analysis of 

 argentic sulphide — must lie between the limits which the two last 

 series of experiments fix. This is equivalent to confirming the accepted 

 value of this constant, so far as any experiments on a scale less exten- 

 sive than those of Stas can be of value to this end. 



While, therefore, this portion of our investigation was not wanting 

 in interesting results, it did not help us to explain the discrepancy we 

 had observed in our experiments on the atomic weight of antimony. 

 We now felt, however, greater confidence in our synthesis of sulphide 

 of antimony; for if the sulphide of silver we had analyzed was so pure 

 there was every reason to believe that the sulphide of antimony pre- 

 pared in the same way was equally pure, save only the small occlusions 

 which were so well known, and had been taken into account. We 

 were therefore now still more fully persuaded that the value 120, which 

 we had obtained for the atomic weight of antimony, must be correct 

 within a few tenths of a unit ; and it seemed to us very clear that the 

 constant error, which had so perplexed us, was to be looked for in the 

 analyses of chloride of antimony. Moreover, it seemed probable to us at 

 this time that we might obtain a clew to the hidden source of error by 

 analyzing the bromide and iodide of antimony before continuing our 

 experiments on the chloride, for the same influences would be likely 

 to afiFect all these processes ; yet it was reasonable to expect that they 

 would act in varying degrees in the three cases, and that they might 

 thus reveal their nature. We begin with our work on the bromide. 



We prepared the bromide of antimony by adding in small portions 

 at a time the pulverized metal to a strong solution of bromine in sul- 

 phide of carbon. The retort containing the solution was kept cool by 



