28 THE ATOMIC WEIGHTS. 



and chlorine. Other ratios have been applied to the deter- 

 mination of the atomic weight of sulphur, but they are 

 hardly applicable here. The earlier results of Berzelius 

 were wholly inaccurate, and his later experiments upon the 

 synthesis of lead sulphate will be used in discussing the 

 atomic weight of lead. Erdmann and Marchand deter- 

 mined the amount of calcium sulphate which could be 

 formed from a known weight of pure Iceland spar ; and 

 later they made analyses of cinnabar, in order to fix the 

 value of sulphur by reference to calcium and to mercury. 

 Their results will be applied in this discussion towards ascer- 

 taining the atomic weights of the metals just named. For 

 our present purposes only three ratios need be considered. 



First in order let as take up the composition of silver 

 sulphide, as directly determined by Dumas, Stas, and Cooke. 

 Dumas'* experiments were made with sulphur which had 

 been thrice distilled and twice crystallized from carbon di- 

 sulphide. A known weight of silver was heated in a tube 

 in the vapor of the sulphur, the excess of the latter was dis- 

 tilled away in a current of carbon dioxide, and the resulting 

 silver sulphide was weighed. 



I subjoin Dumas' weighings, and also the quantity of 

 Ag^S proportional to 100 parts of Ag, as deduced from 

 them : 



.0029 



Dumas used from ten to tliirty grammes of silver in each 

 experiment. Stas,t however, in his work, employed from 

 sixty to two hundred and fifty grammes at a time. Three 

 of Stas' determinations were made by Dumas' method, while 

 in the other two the sulphur was replaced by pure sulphu- 



* Ann. Chem. Pharm., 113, 24. i860 

 f Aronstein's Translation, p. 179. 



