APPENDIX. 



ON DUMAS' CORRECTION AND PROUT'S HYPOTHESIS. 



In the year 1815 Prout put forth his famous hypothesis 

 that the atomic weights of all the elements were multiples 

 of that of hydrogen. His views were adopted by many 

 chemists, but opposed by others; among them Berzelius 

 and Turner; and down to the present day "Front's Law" 

 has been the subject of earnest controversy. Of course the 

 fact was early recognized that in its original form the hy- 

 pothesis could not stand, and accordingly it was modified 

 by Dumas in such manner that half and quarter multiples 

 of the atomic weight of hydrogen were considered as well 

 as the whole numbers. 



But of late years Front's hypothesis, even with its elastic 

 modification, has been in disfavor. Only a few chemists still 

 clung to it as the representative of a veritable law. The 

 researches of Stas were especially directed towards ascertain- 

 ing its truth or falsity ; and his results, as well as those ob- 

 tained by Marignac, were such as to lead most chemists to 

 the belief that it had been forever overthrown. The atomic 

 weights determined by Stas agreed neither with whole, half, 

 nor quarter multiples of that of hydrogen, and the varia- 

 tions seemed to be wholly outside the range of recognizable 

 experimental errors. 



In 1878, however, a probable source of error in some of 

 Stas' researches was pointed out by Dumas.* Many of Stas' 

 ratios had involved the use of pure metallic silver, which 

 had been fused under a cover of borax containing a little 



* Ann. Chim. Phys., (5s.,) 14, 289. 



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