Conductivities and Viscosities in Formamid and in Mixed Solvents. 73 



ther fractionation, however, yielded a product which maintained a high 

 specific conductivity during the same interval of time as the pure 

 solvent. 



Ethyl Alcohol. The ethyl alcohol used in preparing the mixed sol- 

 vents was obtained by refluxing a good grade of commercial alcohol 

 over lime for about 24 hours, then distilling. The middle fraction 

 of about seven-tenths of the total distillate was collected and kept in 

 receiver similar to that described by Lloyd and Pardee. (See Chapter 

 III.) It had a mean specific conductivity of 4.1X10" 7 at 25 and a 

 density of 0.78506 to 0.78507 at the same temperature. 



Mixed Solvents. The mixed solvents containing formamid and 

 alcohol were prepared by weighing directly into glass-stoppered flasks 

 the quantities of each component to make a mixture of the desired 

 weight per cent of each, all weighings being reduced to a vacuum. 



SALTS. 



As in the earlier work, all salts used were carefully recrystallized and 

 dried to constant weight at a suitable temperature depending upon the 

 nature of the salt. In the case of calcium nitrate, the salt was prepared 

 from the purified carbonate, the solution evaporated to dryness, and 

 the salt heated to constant weight at 150, since it was practically 

 impossible to recrystallize it. The aqueous solution showed only 

 traces of alkalinity. 



The formates and the sodium salts of the other organic acids were 

 purified by recrystallization or were prepared from the purified acids. 

 Just before using they were dried to constant weight in the vacuum 

 drying-oven described under the head of apparatus. In the case of 

 all hygroscopic salts the drying process was repeated after weighing 

 out the required amount of salt for the solutions. 



SOLUTIONS. 



All solutions were made up at 20, the more concentrated by direct 

 weighing, those below one-tenth molar by dilution. Special precau- 

 tions were used to protect both solvent and solutions from access of 

 moisture, the procedure followed being essentially that outlined by 

 Davis and Putnam; 25 to 50 cubic centimeters only of each solution 

 were prepared, as this amount was sufficient both for conductivity and 

 viscosity measurements. 



APPARATUS. 



The conductivity apparatus used was identical with that employed in 

 the earlier work. The plate type of cell, previously described, served 

 for measuring the conductivities of solutions both in pure formamid and 

 in the mixed solvents. The cells were carefully standardized at regular 

 intervals. 



