484 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



decomposed one another exactly." Berzelius, whose own 

 numbers had been criticised adversely by Thomson, 1 added 

 that " This investigation belongs to that very small class, 

 from which science can derive no advantage whatever . . . 

 and the greatest consideration which contemporaries 

 can show to the author is to treat this work as if it 

 had never appeared" (Jahresbericht, 1827, 6, 77). 



But Prout's hypothesis was not to be got rid of so easily. 

 Dumas and Stas (p. 150) by bringing down the atomic 

 weight of carbon from 12*25 to ii'97 (H=i) obtained 

 striking evidence that Berzelius's deviations from integral 

 ratios might be due largely to unsuspected experimental 

 errors. So, also, Dumas's experiments on the composition 

 of water (p. 127) which brought down the atomic weight of 

 oxygen from 16-03 to I 5'96, left it still very close to an 

 integral ratio. Many years later, after completing his experi- 

 ments on the equivalents of the elements, Dumas concluded 

 " that the equivalents of the elements are often integral 

 multiples of the equivalent of hydrogen taken as unity," 

 but that in the case of chlorine 2 and certain other elements 

 " the unit with which they must be compared is only 0*5 of 

 the equivalent of hydrogen " (Ann. Chim. Phys., 1859, 55, 

 141). Stas, on other hand, who for many years devoted all 

 his leisure to the elucidation of this problem, began his 

 experiments with " an almost absolute confidence in the 

 exactness of the law of Prout," but when they were com- 

 pleted had " arrived at the complete conviction, the entire 

 certainty, so far as certainty is possible on such a subject, 

 that the law of Prout ... is only an illusion, a pure 

 hypothesis definitely contradicted by experiment " ( Works> 



1 "Berzelius's numbers are in general very near approximations to 

 the truth ; though I am persuaded that in very few instances he has 

 actually reached it" (First Principles, I. xvii.). For a fuller dis- 

 cussion see Mallet's "Stas Memorial Lecture" (Trans. Chem. Soc., 

 1893, 63, 1-56), and Freund, Chemical Composition, chap. xix. 



' 2 Following Pelouze, Actes Soc. Helv. Sci. Nat., 1843, 64. 



