Conductivity of Organic Acids in Ethyl Alcohol. 127 



If we know ^ and the values of // corresponding to two or more 

 values of 17, the equation can be solved for r, the equilibrium constant, 

 and for u u f , the difference between the migration velocity of the 

 cations in anhydrous alcohol and that of the hydrated ion (H 2 0,H) + 

 in aqueous alcohol. Therefore, in order to test the equation, it is only 

 necessary to determine the conductivity at infinite dilution of several 

 organic acids in pure alcohol and in two or more alcohol-water mixtures. 



The greatest experimental difficulty in doing this lay in the prepara- 

 tion of pure absolute alcohol. At first 1 metallic calcium was used for 

 this purpose (von Winkler's method), but the alcohol prepared in this 

 way, although practically free from water, was found 2 to contain con- 

 siderable amounts of ammonia (formed by the action of water upon the 

 calcium nitride present in the calcium); and hence this method had 

 to be abandoned. After further experimentation a satisfactory product 

 was finally obtained in the following manner: 



Ordinary 95 per cent alcohol was allowed to stand in contact with 

 lime for some time and then distilled (Kailan). This treatment 

 reduced the water content to about 0.006-normal, or 0.12 gram per liter. 

 The same process was repeated, this time using a distilling vessel and 

 condenser of copper; and the amount of water present was decreased 

 to 0.003-normal, or 0.06 gram per liter. If a completely anhydrous 

 alcohol was desired, the product of the first distillation was treated 

 with calcium. For this purpose calcium bars were turned on a lathe 

 to remove the coating of hydroxide, and the bright metal was cut into 

 pieces the size of a pea. An amount of calcium equal to ten times 

 the amount of water present (about 0.1 gram) was introduced into the 

 alcohol. The whole was then heated for several hours with a reflux 

 condenser attached, and a rapid stream of dry air was passed through 

 the distillation chamber to remove traces of ammonia. In this way 

 absolute alcohol was obtained having a specific conductivity of 2X 10~ 7 . 



With a good quality of alcohol in his possession Goldschmidt was 

 ready to test his equation, and he began his study with hydrochloric 

 acid. First, the molecular conductivity in absolute alcohol was 

 measured at dilutions ranging from 10 to 5,120 liters; and from the 

 values obtained for the more dilute solutions ju , the conductivity at 

 infinite dilution was calculated with the aid of Kohlrausch's formula 



A^QQ r^v i 



The mean value of yu proved to be 89. Then the conductivity in 

 aqueous alcohol containing different amounts of water (17) was deter- 

 mined over the same range of dilution, and the limiting conductivity, 

 /*,, corresponding to each alcohol-water mixture, was estimated as 

 before. The results show that the molecular conductivity of solutions 



Elektrochem., 15, 4 (1909). 2 Zeit. phys. Chem., 81, 30 (1912). 



