ATOMIC WEIGHTS 25 



Combined, these data give : 



From ratio H:0 15.8792. ± .00032 



Prom ratio HrHoO 15.8785, ± .00066 



General mean 15.8790, ± .00028 



For details Morley's original memoir must be consulted. No abstract 

 can do full justice to it. 



Two other series of determinations, by Julius Thomsen, are radically 

 different in method from all the previous work. In the first series ^ he 

 determined the ratio between HCl and NH3 ; and thence, using Stas' 

 values for CI and N, fixed by reference to = 16, computed the ratio 

 H : 0. This method was so indirect as to be of little importance, and 

 gave for the atomic weight of oxygen approximately the round number 

 16. I shall use the data farther on for another purpose. The paper lias 

 been sufficiently criticised by Meyer and Seubert,' who have discussed 

 its sources of error. 



In Thomsen's later memoir ^ a method of determination is described 

 which is, like the preceding, quite novel, but more direct. First, alu- 

 minum, in weighed quantities, was dissolved in caustic potash solution. 

 In one set of experiments the apparatus was so constructed that the 

 hydrogen evolved was dried and then expelled. The loss of weight of 

 the apparatus gave the weight of the hydrogen so liberated. In the 

 second set of experiments the hydrogen passed into a combustion chamber 

 in which it was burned with oxygen, the water being retained. The 

 increase in weight of this apparatus gave the weight of oxygen so taken 

 up. The two series, reduced to the standard of a unit weight of alu- 

 minum, gave the ratio between oxygen and hydrogen. 



The results of the two series, reduced to a vacuum and stated as ratios, 

 are as follows: 



First. Second. 



Weight of H Weight of O 



Weight of Al Weight of Al 



0.11180 0.88788 



0.11175 0.88799 



0.11194 0.88774 



0.11205 0.88779 



0.11189 0.88785 



0.11200 0.88789 



0.11194 0.88798 



0.11175 0.88787 



0.11190 0.88773 



1 Zeitsch. physikal Chem., 13, 398. 1894. 



2 Ber. Deutsch. chem. Ges., 27, 2770. 



3 Zeitsch. anorg. Chem., 11, 14. 1895. 



