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LIX. The Evolution of the Doctrine of Affinity. 

 By Professor Lothar Meyee, of Tubingen* '. 



IT may not be amiss, on the issue of a Journal f specially 

 devoted to the theoretical and physical aspects of 

 Chemistry, to take a rapid survey of the development of the 

 doctrine of chemical affinity, a correct knowledge of which is, 

 and must ever remain, the most important object of the theory 

 of our science. 



The former doctrines of affinity, conceived without know- 

 ledge of the laws of chemical combination, reached their acme 

 in Berthollet's teaching, which united all previous investiga- 

 tions and speculations into a compact theory. 



The basis of Berthollet's conception was his statement that 

 the chemical action of every substance must be proportional 

 to its active mass and to a constant depending on its nature, 

 and named by him Affinity, except in so far as external con- 

 ditions (e. g. temperature, state of aggregation, solubility, 

 volatility, and so on) acted as retarding or accelerating causes. 

 The doctrine of Berthollet is now fully recognized, although 

 it "was for long ignored or forgotten. This unfortunate 

 neglect is explicable when it is remembered that, along with 

 the most illustrious of his contemporaries, he committed the 

 error of supposing that the capacity for saturation was a mea- 

 sure of affinity. Sir Humphrey Davy had, indeed, shown that 

 this assumption led to not a few difficulties ; but it was first dis- 

 proved by the brilliant experimental development by Berzelius 

 of Richter's " Stoi'chiometry *' and Dalton's Atomic Theory. 



That, in consequence of this disproof of an unimportant and 

 incidental addition to the experimentally correct doctrine of 

 Berthollet, his doctrine should have almost been forgotten, and 

 have been completely neglected, would appear inconceivable, 

 if we did not consider the enormous influence exercised by 

 Berzelius on the growth of Chemistry. He united to an acute 

 perception of the most minute peculiarities in the behaviour of 

 chemical substances, and the most refined choice of analytical 

 and synthetical methods, a special talent for systematic 

 arrangement of facts discovered from day to day by himself 

 and by his students. All theoretical views were employed by 

 him in support of his system ; indeed, he accepted none unless 

 it proved of assistance in his endeavour to perfect his mar- 

 vellous arrangement of the chemical elements and their com- 

 pounds. He was indifferent to theoretical speculations which 



* Translated and communicated by Professor William Ramsay, 

 t Zeitschrift fur physikalische Chemie, edited by W. Ostwald and 

 J. van't Hoff (Eiga and Leipsig). 



