THE SYNTHESIS OF ARGENTIC CHLORIDE. 57 



THE SYNTHESIS OF ARGENTIC CHLORIDE. 



Many accurate analyses were made by Stas which involve more 

 or less directly the atomic weight of chlorine, but of these we are 

 concerned in the present paper only with those which compare silver 

 with chlorine, because such alone could cause an error leading to the 

 discrepancy under discussion. The experimental solution of the 

 problem is thus a comparatively simple matter, to be accomplished by 

 combining silver with chlorine. Among all Stas's experiments there 

 seems to have been only seven which dealt directly with this ratio.* 

 These were carried out by two methods. Of these methods one, the 

 ignition of silver in a stream of chlorine, is acknowledged by Stas to 

 possess errors which he could not wholly correct. Hence the three 

 experiments made by this method are of doubtful value, and only four 

 analyses remain for the purpose of obtaining directly this very important 

 ratio. Even in these the large glass globes employed were more or less 

 attacked by the strong acids or the fused chloride, and, moreover, Stas 

 questioned the purity of the silver used in one case.f There is obviously 

 no doubt of the need of obtaining more light upon this matter. 



The fundamental requirements of a satisfactory synthesis of argentic 

 chloride are as follows: First, that the silver must be pure; secondly, 

 that it must all be collected in the argentic chloride, and thirdly, that 

 this argentic chloride must be pure. Because all the error accumulates 

 upon the consequent atomic weight of chlorine and is magnified in 

 calculation, the requirements are usually rigorous. 



The fulfilling of the first of these requirements has already been 

 treated in detail, under the discussion of the preparation of silver. 

 Our knowledge of the essentials of this easy but subtle process grew 

 as the quantitative work on the synthesis of the chloride progressed. 

 Whether in the future anyone may be able to discover an unsuspected 

 source of impurity in our purest silver, is of course impossible to say. 

 At least, there can be no doubt that it was of distinctly a higher grade 

 than the silver used by Stas in most of his work. 



In order to convert this silver wholly into the chloride without 

 loss or illegitimate gain, two methods were used, for fear that in one 

 of these a constant error might lurk unsuspected. The first consisted 

 in the usual method of solution in nitric acid and precipitation in 

 dilute solutions, being essentially similar to that used in obtaining the 

 ratio between common salt and silver chloride. The weighed silver 



*Stas,Untersuchungen (trans. Aronstein) 173, 175 (1867), Ex Oeuvr., 1,333- 

 tStas (Aronstein), pp. 117, Oeuvres, l,p. 330. 



