Messrs Jones and Richardson, On Hydrogen Ions. 337 



Note on a Method for determining the Concentration of Hydrogen 

 Ions in Solution. By H. O. Jones, B.A., Clare College, and O. W. 

 Richardson, B.A., Coutts Trotter Student, Trinity College. 



[Bead 3 February 1902.] 



The following investigation was suggested by a series of obser- 

 vations by Mr Fenton and one of the authors 1 . They showed that 

 oxalacetic hydrazone decomposed in presence of water at 100°C. 

 into carbon dioxide and pyruvic hydrazone. In the presence of 

 strong acids, however, the reaction proceeded differently and 

 pyrazolone carboxylic acid and water were formed. With weak 

 acids or very dilute strong acids the two reactions occurred simul- 

 taneously and it was shown that the amounts of carbon dioxide 

 given off, using acids of the same normality, were in the inverse 

 order of their " affinity constants." 



It was suggested that these reactions might be explained by 

 supposing that the formation of pyruvic hydrazone was due to the 

 decomposition of the negative ion according to the following 

 equation : 



- + 

 COOH . C . CH 2 . C0 2 + H = C0 2 + COOH . C - CH 3 (1) 



II II 



N.NH.C 6 H 5 N.NH.C 6 H 5 ; 



whereas the undissociated molecule decomposed as follows : 



CH 2 -CO.OH CH 2 -CO 



I H | | 



C : N . N . C 6 H 5 = C : N . N . C 6 H 5 + H 2 0. (2) 



I I 



C0 2 H C0 2 H 



The effect of acids would thus be to diminish the concentration of 

 the negative ion and hence to reduce the amount of carbon 

 dioxide produced. 



The experiments here described were undertaken with the 

 view of further developing this hypothesis, and of testing its 

 quantitative validity. The theoretical problem is one of some 

 complexity, since it is necessary to take into account the simul- 

 taneous occurrence of two reactions, the products of each of which 

 exert an effect on the rate at which the other proceeds. In the 

 case where the concentration of the hydrogen ions due to the 

 hydrazone is negligible compared with that due to the acid used, 



1 Fenton and Jones, Jour. Ghem. Soc. 1901, lxxix. p. 91 ; Proc. Chem. Soc. 1901, 

 p. 24 ; Proc. Camb. Phil. Soc. xi. 2, p. 108. 



