M. J. Thomseir's Thermo- chemical Researches. 417 



The author has made some analogous experiments with a great 

 number of acids. In none of those which he has examined 

 is the avidity equal to that of nitric acid and hydrochloric acid ; 

 but it is in some superior, in others inferior to that of sulphuric 

 acid; in some it is almost nothing. He announces the forth- 

 coming publication of these results, and passes now to the com- 

 parison of his observations with Berthollet's law. 



According to Berthollet, the division of a base between two 

 acids takes place in proportion to its affinity for those acids and to 

 their respective masses. Now the masses are proportional to the 

 chemical equivalents A and A' of the acids, and to the numbers 

 a and a 1 of equivalents of each of them which are placed in the 

 presence of the base. Therefore if we denote their respective 

 affinities for that base by x and a 1 , we shall have for the ratio 

 according to which the division of the base is effected : — 



aKx 



But that which Berthollet designated the affinity of the acids 

 was no other than that which was called their capacity of satura- 

 tion — that is to say, the inverse of their chemical equivalents ; so 

 that this formula becomes simply 



and the base ought to divide itself between two acids in propor- 

 tion to the number of equivalents of the latter. 



Hence, in the presence of equal equivalents of sulphuric acid 

 and nitric acid, soda ought to divide itself equally between them. 

 Therefore Berthollet's law is not confirmed by experiment. The 

 majority of modern authors have interpreted the law of Berthol- 

 let in a sense less conformable to its strict expression, but more 

 in harmony with the ideas which have given rise to the theory of 

 chemical equivalents, by attributing to the word affinity a sense 

 analogous to that which its author attributes to the term avidity, 



compared a bibasic acid with two monobasic acids, so that, the relative 

 energies of these acids not being very different, the division occurs in such a 

 manner as to produce a neutral nitrate and a bisulphate — equivalent quan- 

 tities of sulphuric acid and nitric acid or hydrochloric acid remaining free 

 in the liquid, as may be seen from the formula : — 



3NaO, S0 3 + 3HO, N0 5 = 2NaO, N0 5 + HO, NaO, 2S0 3 +HO, NO 5 

 + HO, SO 3 . 



If we assume that this is the principal cause of the division which the 

 base undergoes, it remains to be known whether the influence of the degree 

 of energy of the acids has not the effect of slightly modifying this state of 

 equilibrium. But in order to be able to verify this supposition, it would be 

 necessary to attribute to the experimental data a precision of which they do 

 not appear susceptible, for reasons which I shall hereafter explain. — CM.] 



Phil Mag. S. 4. Vol. 39. No. 263. June 1870. 2 E 



