HYDROGEN. 57 



was precipitated as barium salt, and the atomic weight cal- 

 culated by comparison of the gold employed and the barium 

 sulphate obtained. 1000 gold gave 1782 sulphate. [If the 

 atomic weight of S = 32.0742, and that of Ba = 137.08, the 

 above value follows.] [Annal. de Chimie et de Phys., (3,) 30, 

 1850, 355.) 



HYDROGEN. 



The density of hydrogen as determined by a great num- 

 ber of investigators, especially Regnault, is about y^g of that 

 of oxygen. If oxygen is 16, the atomic weight of hydrogen 

 is consequently about 1. 



The atomic weights of the elements are compared either 

 with that of oxygen or with that of hydrogen. The main 

 advantage of assuming hydrogen as unity is the simplicity 

 of the approximate values expressed in terms of the atomic 

 weight of this element. The hypothesis of Prout has also 

 had much influence in giving currency to this unit. The 

 advantages of oxygen as a standard of comparison consist 

 in the fact that it combines with all the elements, except 

 fluorine, and in the superior accuracy of the determination 

 of its specific gravity. The percentage variation between 

 Regnault's determinations of the specific gravity of hydrogen 

 was thirty-six times as great as occurred in his experiments 

 on oxygen. Unnecessary complication in the approximate 

 values of the atomic weights is as well avoided by assuming 

 oxygen at 16 as by taking hydrogen at 1. 



These reasons for the adoption of the atomic weight of 

 oxygen as a standard of comparison appear to me conclu- 

 sive, and accordingly all values in this paper have been re- 

 duced to = 16. 



F. H. WoLLASTON : 1.06 (0 = 16 ); 6.64 (O = 100). 



Gay-Lussac and Humboldt having shown that two vol- 

 umes of hydrogen and one of oxygen form water, and Biot 

 and Arago having determined the specific gravity of these 

 gases, Wollaston calculated the above atomic weight. iPhiL 

 Trans., IO4,, 1814, 20.) 



Berzelius and Dulonq : 0.9984. (0 = 16) ; 6.24 (O 

 = 100). 



Determined by three experiments on the reduction of 

 cupric oxide by hydrogen. The hydrogen was made from 



