ATOMIC WEIGHTS 



133 



The third sulphur ratio to be considered is one of minor importance. 

 When silver chloride is heated in a current of sulphuretted hydrogen the 

 sulphide is formed. This reaction was applied by Berzelius ' to deter- 

 mining the atomic weight of sulphur. He gives the results of four 

 experiments; but the fourth varies so widely from the others that I 

 have rejected it. I have reason to believe that the variation is due, 

 not to error in experiment, but to error in printing; nevertheless, as I 

 am unable to discover the cause of the mistake, I must exclude the figures 

 from our discussion. 



The three available experiments, hoAvever, give the following results. 

 The last column contains the ratio of silver sulphide to 100 parts of 

 chloride : 



6.6075 grm. AgCl. gave 5.715 grm. AgoS. 86.478 



9.2S23 " 7.98325 " 86.471 



10.1775 " 8.80075 " 86.472 



Mean, 86.4737, ± .0015 



We have also a single determination of this value by Svanberg and 

 Struve." After converting the chloride into sulphide they dissolved the 

 latter in nitric acid. A trifling residue of chloride, which had, been 

 enclosed in sulphide, and so protected against change, was left undis- 

 solved. Hence a slight constant error probably affects this whole ratio. 

 The experiment of Svanberg and Struve gave 86.472 per cent, of silver 

 sulphide derived from 100 of chloride. If we assign this figure equal 

 weight with the results of Berzelius, and combine, we get a general mean 

 of 86.4733, ±.0011. 



The work done by Richards ^ relative to the atomic weight of sulphur 

 is of a difl'erent order from any of the preceding determinations. Sodium 

 carbonate was converted into sodium sulphate, fixing the ratio' Na.^COa : 

 XaoS04 : : 100 : x. The data are as follows, with vacuum weights: 



' Berzelius' Lehrbuch, 5 Aufl., 3, 1187. 



2Journ. prakt. Chem., 44, 320. 1848. 



' Proe. Amer. Acad., 26, 268. 1891. Incidental to work on the atomic weight of copper. 



