SOLVENTS. 173 



with soda lime. Water purified in this manner had a conductivity of from 

 1 x 10- 6 to 1.5 x 10- 8 at 0, and from 1.8 X lO" to 2.5 X lO' 6 at 25. 



METHYL, ALCOHOL. 



The methyl alcohol used was the best that could be obtained commercially. 

 It was purified by boiling over calcium oxide for several days, and then dis- 

 tilled into a glass-stoppered bottle containing anhydrous copper sulphate, 

 where it was allowed to stand for at least a month before using. To prepare 

 the alcohol for final use, it was distilled from the copper sulphate into a bottle 

 carefully protected from moisture, the first and last 150 c.c. of the distillate 

 being discarded. The conductivity of the methyl alcohol thus prepared was 

 practically the same as that of the water. 



ETHYL ALCOHOL. 



The ethyl alcohol was purified in the same manner as the methyl alcohol, 

 and gave an average value for conductivity of from 2 x 10~ 7 to 3 x 10~ 7 at 

 0, and from 5 X 10~ 7 to 7 x 1CT 7 at 25. 



ACETONE. 



The acetone was dried over fused calcium chloride for about one month, 

 and then distilled immediately before using, in the same manner as the alcohol. 

 Its average conductivity was about 3 X 10~ 7 at 0, and 4 x 10~ 7 at 25. 



SOLUTIONS. 



In making up the mixed solvents and in diluting the solutions to any given 

 volume, care was taken to bring all solvents and solutions to exactly 20 

 before making the measurements or dilutions. In all cases when one solvent 

 was mixed with another, or a salt was dissolved in a solvent, the solution was 

 brought to 20 before making up to the complete volume. The mixed solvents 

 were made up as designated by Jones and Bingham, 1 i. e., "xc. c. of acetone 

 diluted to 100 c. c. was designated as a mixture of x per cent acetone." 



The mother-solutions were prepared by weighing the salt directly into the 

 measuring flask and diluting with the solvent to a known volume. From 

 this mother-solution the other solutions were prepared by dilution to the 

 desired volume. Whenever this would require the use of less than 5 c. c. of 

 the mother-solution, a more dilute mother-solution was prepared, and from 

 this the successive dilutions were made. 



CONDUCTIVITY MEASUREMENTS. 



Four readings were taken with each solution, using a different resistance 

 for each reading. The cell constants were determined in the usual way by 



1 Amer. Chem. Journ., 34, 494 (1905). 



