80 THE ATOMIC WEIGHTS. 



SULPHUR. 



The atomic weight of sulphur has been determined by means of four 

 ratios connecting it with silver, chlorine, oxygen, sodium and carbon. 

 Other ratios have also been considered, 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 toward ascer- 

 taining the atomic weights of the metals just named. 



First in order let us 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 crys- 

 tallized from carbon disulphide. A known weight of silver was heated 

 in a tube in the vapor of the sulphur, the excess of the latter was distilled 

 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 : 



9-9393 grm. Ag= 1.473 •'^- Ratio, 114.820 



9.962 " 1.4755 " " 114.811 



30.637 " 4.546 " " 114-838 



30.936 " 4.586 " " 114.824 



30.720 " 4.554 " " 114.824 



Mean, 1 14.8234, ± .0029 



Dumas used from ten to thirty 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 

 sulphuretted hydrogen. In all cases the excess of sulphur was expelled 

 by carbon dioxide, purified with scrupulous care. Imj^urities in the 

 dioxide may cause serious error. The five results come out as follows 

 for 100 parts of silver : 



.0007 



*Ann. Cheni. Pharm., 113, 24. lE 

 f Aronstein's translation, p. 179. 



