72 CONDUCTIVITIES OF ORGANIC ACIDS 



The results in the latter case did not agree with those in the former 

 by about 0.2 c.c., 10 c.c. of acid being employed in each case. That 

 the difference was not due to carbon dioxide which might have been 

 dissolved in the sulphuric acid, can be seen from the fact that the same 

 difference appeared in the titrations with an organic acid dissolved in 

 absolute alcohol in which carbon dioxide is not very soluble. 



It was found that if the same quantity of phenolphthalein or coralline 

 used when making the ordinary titrations was added either to pure 

 alcohol or to water, and if these solutions of the indicators alone were 

 titrated against the alkali and then back against the standard acid, 

 an appreciable quantity of alkali was required to change the color in 

 one direction, and about as much of the standard acid to change it in 

 the reverse direction, the alkali and acid being of very nearly the same 

 strength. Corrections for the amounts of alkali and acid necessary to 

 produce such color changes were then applied to the titration volumes 

 of the sulphuric acid and alcoholic potash, when agreement to within 

 the limits of experimental error was obtained between the results for 

 the two indicators. 



In all the titrations in which alcoholic potassium hydroxide was used 

 its temperature was recorded, and when different from 25, which was 

 chosen as the standard temperature, a volume correction was applied. 

 It was easy, and was found necessary as well, to keep all the other 

 solutions, particularly those of the organic acids in alcohol, as well as 

 the alcoholic potash, at the standard temperature. 



The titration values of the ammonia and standard acid were also 

 corrected, as just stated, for the amounts necessary to produce color 

 change, and the concentration of the ammonia was then calculated. 

 The normality of 1-2-4 dinitrobenzoic acid in alcohol was determined 

 from this standardized ammonia, making the same corrections as 

 above; and it agreed to within 0.2 per cent with that obtained by 

 means of potassium hydroxide. Similar corrections were, therefore, 

 applied to the titrations of all the organic acids. 



The sulphuric acid used to standardize the alkali was made up in 

 large quantity, and its normality determined by the usual barium- 

 sulphate method. 



Owing to the large amount of preliminary work required, it has been 

 possible up to the present to make conductivity measurements of only 

 9 organic acids. The same methods of purifying the acids were 

 employed as when the conductivities of these acids were determined in 

 aqueous solution. In most cases the various dilutions were made up 

 by directly weighing the acid. 



In the work in alcohol it was necessary to discard all of the weaker 

 organic acids; this, in spite of the fact that our cell constants were about 

 eight times smaller than those of Wildermann. After trying acetic 

 acid several times, we gave up hope of obtaining satisfactory results 



