476 Dr. A. Findlay. On a Method of Calculating Solubilities, 



temperatures, viz., and 25 '2, the values of the constant were 

 calculated at 10, 40, 60, 80, 100, by means of the integrated 

 form of the van't Hoff equation : 



1 T- 1 T- 



log, K! - log,, R 2 = FT - 



the value of q, the heat of reaction, being regarded as constant and 

 equal to - 77 '4 centuple calories:* R is the "gas constant." The 

 error introduced here can scarcely be very large. 



Table VI. 



As can be seen from the above figures, the agreement between the 

 calculated and determined values of the equilibrium constants is 

 exceedingly good, especially when one considers how different the two 

 reactions are in character and also that in one case the equilibrium 

 constant increases, in the other case, diminishes with the temperature. 



So far, this is the only case in which I have been able to test the 

 application of the formula R = R' + c (t 1 - () to the calculation of 

 equilibrium constants. On account, however, of the analogy existing 

 between the change of the vapour pressure, solubility, and equilibrium 

 constant, with the temperature, it may be confidently expected that 

 when other cases come to be tried, confirmation of the relationship 

 will be obtained. 



On account of the practical importance of the above relationships, I 

 have thought it well, in this preliminary note, to publish them in the 

 present empirical form. I hope, however, at a later time, to discuss 

 the question in greater detail, with the help of a larger number of 

 examples, and also to examine the subject from the theoretical stand- 

 point. It may, however, be remarked here, that the whole work has 

 been based on the form of the thermodynamic equation given by 



van't Hoff, % eX = ^ , an equation which at once shows the 

 ~ 



Cut 



Koeliclien, loc. cit. 



