OF CERTAIN ORGANIC ACIDS IN AQUEOUS SOLUTIONS. 61 



itself in every case studied, but a large number of exceptions present 

 themselves in the decrease due to increasing dilution. No doubt this 

 is the result of hydrolysis. 



TABLE 21. 

 [Temperature coefficients, 35-50; F=1024.] 



In all the acids that Smith studied, the percentage temperature 

 coefficients of conductivity are small and are of the same order of 

 magnitude. The decrease is regular as the temperature rises. This 

 indicates that some constant factor has influenced the solution, 1 such 

 as the viscosity of the medium. 



The isomeric acids have been the subject of a large amount of investi- 

 gation. Ostwald, 2 Walker, 3 and Derrick 4 have worked on the correla- 

 tion of ionization and structure for such acids, and on the effect of 

 substitution. This work has confirmed the following statement of 

 Springer and Jones : 



"In the case of isomeric acids containing two carboxyl groups, the acid with 

 these groups in the 'ortho' or the 'cis' position is always the stronger." 



K = 154 

 K = 11.3 

 K = 35.8 

 K = 7.8 



Maleic (cis) 35, 

 Fumaric (trans) 35, 

 Citraconic (cis) 35, 

 Mesaconic (trans) 35 C 



o-Bromobenzoic 35, too strong to give a constant. 



o-Toluic 35, 

 m-Toluic 35, 

 p-Toluic 35, 

 w-Bromobenzoic 35 



K = 1.25 

 K = 0.55 

 K = 0.44 

 K = 1.55 



Euler 5 showed that the conductivity of organic acids is a parabolic 

 function of the temperature. This was also brought out by the work 

 of White and Jones. Wightman and Jones, and Springer and Jones 

 plotted curves, using conductivities as ordinates and temperatures as 

 abscissas, and calculated the conductivity of a number of acids from 

 Euler's formula : ^ = ^ + at _ b ? 



This was always found to hold. It holds also in this work. 



The dissociation of a large number of organic acids decreases with 

 rise in temperature. As mentioned above, in certain cases the per- 

 centage dissociation apparently attains a maximum at one of the inter- 

 mediate temperatures, usually at 25 or 35. This has been observed 

 and noted in the publications of Euler, 6 Schaller, 7 White and Jones, 8 



'Jones and West ; Amer. Chem. Journ., 34, 418 (1905). 

 2 Zeit. phys. Chem., 3, 170 (1889). 

 Mourn. Chem. Soc., 61, 605 (1892); 67 147 (1895). 

 4 Journ. Amer. Chem. Soc., 33, 1881 (1911) ;34, 74 (1912). 



"Zeit.phys. Chem. ,21, 257 (1896). 



*Ibid., 21, 247 (1896). 



">Ibid., 25, 497 (1898). 



8 Amer. Chem. Journ., 44, 196 (1910). 



