ELISHA MITCHELL SCIENTIFIC SOCIETY. 109 



Out of 66 elements the revisers agree on 29 to the tenth place of 

 decimals, differing in the hundredth place only. In the reclam- 

 ing '-)!, or 56 per cent., the differences are mure or less great. 



The increased interest in these re determinations of atomic 

 weights, giving fresh data for calculation and enabling us to 

 throw off some of the burden of faulty determinations, gives 

 promise of an approximately correct table in the near future. 



I cannot close without adverting to the speculations of some 

 authors as to the question whether we are to expect these atomic 

 weights to be fixed quantities. In other words, 



ARE THE ATOMIC WEIGHTS CONSTANT? 



This question Stas proposed to himself, before starting upon 

 his classic work on the atomic weights. The conclusion he drew 

 from his experiments was that they were unchangeable. The 

 question has been raised again by Schiitzenberger and Butlerow.* 

 Butlerow does not doubt the results obtained by Stas, but slig- 

 hts that under changed conditions or with different bodies the 

 results might have been otherwise. 



Of course, if the atomic weights are not constant, the law of 

 constant proportions is without support and must be given up, 

 and this would necessitate a revolution in chemistry as a science 

 These authors suppose the range of variation in the weights 

 to be verv slight, yet distinctly to be detected bv analysis. The 

 theories of both are supported by analytical data, in which the 

 authors seem to place the utmost confidence. If their results 

 art' not accurate, the variability of the atomic weights stands 

 unproven. To show the nature of their experiments, Sebelien 

 quotes from Schutzenberger's work his synthesis of water. Ac- 

 cording as this is carried out with copper oxide, at red heat, or 

 by the lowest possible temperature, or with lead chromate, the 



*Bull. de la Soc. Chim. de Paris, 39, 258. 

 *BulI. de la Sue. Chim. de Paris 39, 263. 



Cited in Zeitschrift fur Anal. Chemie, 22, 640, and Sebelien. Geschichte 

 der Atomgewichte, 5 I. 



