542 SCIENCE PROGRESS. 



more experiments a direct comparison with silver, preferably 

 by Stas' method, we are hardly entitled to use Stas' numbers 

 for the atomic weights of chlorine and nitrogen. 



One point ought to be noticed which strongly corrobo- 

 rates the lower value for oxygen (or the higher value for 

 hydrogen), and that is that in many cases we have the atomic 

 weight determined in units derived from oxygen as well as 

 also directly compared to hydrogen. Take, for instance, 

 Mallet's paper (4) " On the Atomic Weight of Aluminium ". 

 There we have — 



Al = 2 7 '07 5 from ammonia alum 



27*046 from aluminium bromide 



2 7 "0605 mean value if O = 15 '96 

 2 7 '005 from volumes of hydrogen evolved 

 2 6 '998 from water produced from the hydrogen 

 evolved 



27.0015 mean value if H = 1 



hence 15*96 x — '- ? = 15*925 may be taken as the atomic 



27*0605 



weight of oxygen if H = 1. 



The estimation of the bromine in a brominated hydro- 

 carbon, or the synthesis of hydrochloric acid by means of 

 silver chloride or the chloride of a metal less volatile, or by 

 some volumetric or other method, would give most valuable 

 results. 



At the present time, therefore, it would be premature to 

 say that we have settled beyond doubt the relative atomic 

 weights of hydrogen and oxygen. 



BIBLIOGRAPHY. 



(1) DALTON, J. A new system of Chemical Philosophy, p. 143. 



Manchester, 1808. 



(2) PROUT, W. Thomson's Annals of Philosophy, vol. vi., 321, and 



vol. vii., 1 1 1, 1 8 16 and 181 7. 



(3) PROUT, W. Letter to Professor Daubeny, Sept. 12, 1831, in 



Daubeny's Introduction to the Atomic Theory. Oxford, 1831. 

 {4) Mallet, J. W. The Atomic Weight of Aluminium, Phil. 

 Trans., clxxi., 1003-1035, 1880. 



