Conductivity of Organic Acids in Ethyl Alcohol. 125 



true and pseudo acids in aqueous alcoholic solutions containing different 

 percentages of alcohol. If it is desired to test whether a given hydrogen 

 compound is a pseudo acid or not, a true acid with approximately the 

 same affinity constant is selected, and the molecular conductivity of 

 both is determined in aqueous alcohol at a given dilution. Then, 

 without varying the dilution, the percentage of alcohol is increased and 

 the resulting conductivities determined. If the molecular conductivity 

 of the hydrogen compound decreases much more slowly than that of 

 the true acid, it is a pseudo acid. Hantzsch and Voegelen offered no 

 explanation for this difference in behavior, but they supported their 

 discovery with widely different examples. 



In the last few years Heinrich Goldschmidt 1 has applied the con- 

 ductivity method to alcoholic solutions of organic acids, in order to 

 determine the equilibrium hydrogen ion-alcohol-water, and he has 

 succeeded in throwing new light on the mechanism of esterification and 

 on the formation of complex ions. 



In his earlier work (1895) on the kinetics of esterification in alcoholic 

 solutions of organic acids, Goldschmidt had observed that the catalytic 

 action of strong acids in accelerating esterification was greatly dimin- 

 ished by the addition of water. He explained this on the assumption 

 that the accelerating action of a strong acid was due to the formation 

 of a complex molecule by union of the acid with alcohol, and that the 

 retardation was brought about by the decomposition of this molecule 

 by water. For example, if hydrochloric acid were acting as the cata- 

 lyzer, a compound C 2 H 5 OH, HC1 would be formed, and this would be 

 acted upon by water according to the equation 



C 2 H 5 OH, HC1+H 2 -=. C 2 H 5 OH+H 2 0, HC1 (I) 



For a time 2 Goldschmidt thought that only the ionized portion of the 

 complex molecule took part in the esterification, and from measure- 

 ments of reaction velocity he undertook to determine the equilibrium 

 in the reaction 



(C 2 H 5 OH, H+) +H 2 ^ C 2 H 5 OH+ (H 2 O, H+) (II) 



He found that a number of organic acids which were esterified in the 

 presence of hydrochloric acid showed the same retardation when equal 

 volumes of water were added. From this he concluded that his 

 assumption was correct, and for the equilibrium 



C(c 2 H5OH, H ) X 





H 



he calculated the equilibrium constant r to be 0.15. 



iZeit. Elektrochem., 15, 4 (1909) ; Zeit. phys. Chem., 70, 627 (1910) ; Ibid., 81, 30 (1912) ; Zeit. 

 Elektrochem., 20, 473 (1914); Zeit. phys. Chem., 89, 129 (1914). 

 2 Zeit. phys. Chem., 60, 728 (1907). 



