SILVER, POTASSIUM, ETC. 31 



The third and hist sulphur ratio with which we have now 

 to deal is one of minor importance. When silver chloride 

 is heated in a current of sulphuretted hydrogen the sul- 

 jjhide is formed. This reaction was applied by Berzelius* 

 to determining 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 

 track out the cause of the mistake, I must exclude the fig- 

 ures involving it entirely from our discussion. 



The three available experiments, however, give the fol- 

 lowing results : The last column contains the ratio of silver 

 sulphide to 100 parts of chloride. 



6.6075 grm- AgCl gave 5.715 gmi. Ag^S. 86.478 



9.2323 " 7-98325 " 86.471 



10.1775 " 8.80075 " 86.472 



Mean, 86.4737, dz .0015 



We have also a single determination of this value by 

 Svanberg and Struve.f 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 undissolved. 

 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. 



For sodium there are but two ratios of any definite value 

 for present purposes. The early work of Berzelius we may 

 disregard entirely, and confine ourselves to the considera- 

 tion of the results obtained by Penny, Pelouze, Dumas, and 

 Stas. 



* Berzelius' Lehrbuch, 5th Ed., Vol. 3, p. 1187. 

 f Journ. fur Prakt. Chem., 44, 320. 1848. 



