182 Mr. M. M. Puttison Milli- 



on 



another ; Bcrthollet considered also the masses of the acting 

 bodies and the physical actions which aided the purely che- 

 mical changes. A substance with a small affinity for either 

 of the constituents of another substance was nevertheless, ac- 

 cording to Berthollet, capable of decomposing the other, pro- 

 vided the mass of the first substance was large compared with 

 that of the second. The affinity of an acid is in this view 

 greatest for that base with which it combines in smallest 

 quantity, because, if the affinity be large, the mass must be 

 small as compared with the mass of another base which has a 

 small affinity for the given acid ; otherwise equal amounts of 

 chemical work would not be done in forming each of the neu- 

 tral salts. 



The theories of Bergmann and Berthollet were antagonistic. 

 Since the year 1803 chemists have now inclined to one, 

 now to another. Modifications have been made in each; but 

 no new important theory has been advanced. 



The most important contributions made within recent years 

 towards the final solution of the problem of chemical affinity 

 are contained in two papers by Guldberg and Waage, and 

 three papers by W. Ostwald. 



The object of this paper is to give an account of the results 

 obtained by these naturalists. 



The first paper by the two Christiania Professors was pub- 

 lished in 1867, and is entitled " Etudes sur les affinites chi- 

 miques;" the second paper by the same authors appeared in 

 the March number of the present year of the Journal fiXr 

 praktische Cltemie. Ostwald's papers, entitled " Volumche- 

 mischen Studien," are to be found in Pogg. Ann. Erganzg. 

 Bd. viii. p. 154, and in Journ. prakt. Chem. [2] xvi. 385, and 

 xviii. 328. 



Guldberg and Waage do not attempt to formulate a general 

 theory of chemical action ; they confine themselves to a con- 

 sideration of the action of mass in chemical changes. The ex- 

 planation which they give of this action is singularly simple, 

 and so exact as to allow of mathematical deductions being 

 made, which are shown to hold good by the results of expe- 

 rimental researches. 



Ostwald considers the measurement of affinity as exerted 

 between acids and bases in solution combining together to 

 form salts which are soluble under the experimental conditions. 

 Berthollet's statement, " Toute substance qui tend a entrer 

 en combinaison, agit en raison de son affinite et de sa quan- 

 tite " (Statique Chimique, p. '2), has been extended and ren- 

 dered more exact by the researches of Guldberg and Waage. 

 These naturalists have given a definite meaning, independent 



