CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



THE STANDARD OF ATOMIC WEIGHTS. 

 By Theodore William Richards. 



Received July 27, 1901. 



The long continued discussion concerning the relative advantages of 

 hydrogen and oxygen as standards of the numerical values of chemical 

 combining weights seems to need yet another word. In spite of the 

 fact that an international committee has decided by a large majority 

 in favor of oxygen, the opposing arguments have not been put to rest. 



The latest paper on this subject is by Erdmann,* the well known 

 champion of the old unit value for hydrogen and the new value for 

 every other atomic weight. The paper consists mainly of a partial 

 reply to an earlier paper by Brauner.f The weight of the argument 

 in these papers seems to be distinctly on Brauner's side, but it is not 

 my purpose to recapitulate all the arguments which these gentlemen 

 and others have advanced. $ I wish rather to call attention to a few 

 points which do not seem to have received the attention which they 

 deserve. 



The first of these concerns the question of fact. What element has 

 served as the actual standard of comparison in a plurality of cases ? 

 The question is easily answered by referring to Clarke's valuable 

 compilation. § 



Evidently hydrogen in combination has been weighed accurately only 

 in the cases of water and the ammonium salts. The atomic weights of 

 zinc, aluminum, iron, nickel, cobalt, and gold have been determined by 



* Zeitschrift fiir anorg. Chera., 27, 127 (1901). 



t Zeitschrift fiir anorg. Chem., 26, 186 (1901). 



J A recent recapitulation of many of the arguments on each side may be 

 found in the report of the American Chemical Society's hranch of the International 

 Committee, published in the Journal of the American Chemical Society, February, 

 1901, p. 44 of the Proceedings. 



§ F. W. Clarke, A Recalc. of the At. Weights, Smithson. Misc. Coll., The Con- 

 stants of Nature, Part V. (1897). 



