382 



REPORT 1886. 



The formula used is that of § 10- 

 (l-.r)(l- 



.r) a6 = .r'^ fl y, 



•where r = 1, except for H^SO^, when r = 2, and for HjPO^, when r = 3. 

 lowing table gives the results : — 



The fol- 



Relative Avidity of Acids. 



Ostwald specially says that his numbers iuTolve considerable uncertainties, so 

 the agreement is sufficient. 



§ 23. Eeview of anterior theories. 



Finally, the author reviews the theories of Berthollet, Berthelot, and Guldberg 

 and Waage. He points out that many objections to views expressed in Berthol- 

 let's essay of 1803 are met and removed by his own theory. He regards these views 

 as true, but as requiring amplification and additional statements which he supplies. 



The theory of Berthelot is based on this principle — ' Every chemical change, 

 accomplished without the intervention of foreign energy, tends towards the 

 production of that body or system of bodies which liberates most heat.' The 

 ' energy of dissociation,' however (which it is necessary to postulate), deranges 

 conclusions from this principle, especially at high temperatures. On this ground 

 M. Lothar Meyer and M. Ostwald state that there are a great number of cases to 

 which Berthelot's principle cannot be applied, and that it is of but small value in 

 predicting . results. 



As to Guldberg and Waage, he says their theory develops itself slowly from 

 1864 to 1879 in three distinct stages. In the first two memoirs they postulate 

 ■' forces of action ' acting between substances, and in the first they give the equation 



b' 



a(p- .r)« (p - .v) >> = a,{p, + .i)"\q^ + x) 



where the indices may be quite different ; and they oppose the view of Berthollet 

 that affinity is proportional to mass. 



In their second memoir they put all the indices = 1, and so abandon this 

 ground. But they still continue the hypothetical ' forces of action.' Arrhenius 

 objects to these forces as uncalculable and unnecessary. 



In their third memoir G. and W. introduce the idea of a portion only of each 

 body taking part in the reaction, and think of the number of encounters between 

 such active molecules, and so of the velocity of the reaction, much the same as 

 Arrhenius does. 



For heterogeneous systems G. and W. think the surface of the solid present 

 exerts an influence ; but A. says it cannot, or it would vary with the extent of 

 surface, which it does not. In § 13 (p. 377), he says, is cited an experiment fatal 

 to the theory of Guldberg and Waage, according to M. Ostwald, but not inexplicable 

 by the new theory. 



Sesume. 



' In the present part of this work we have first shown the probability that 

 electrolytes can assume two different forms, one active, the other inactive, such that 

 the active part is always, under the same exterior circumstances (temperature and 

 dilution), a certain fraction of the total quantity of the electrolyte. The active part 

 conducts electricity, and is in reality the electrolyte ; not so the inactive part. 

 Moreover, we have proved that the necessary consequence of the hypothesis of 



