132 Conductivities and Viscosities in Pure and in Mixed Solvents. 



It was then nearly filled with the solution which had been made up and 

 placed in the 15 bath. The measuring-flask containing the remainder 

 of the solution was returned to the 25 bath. In this way four dilutions 

 of each acid were prepared N/8, N/32, N/128 and N/512; and the 

 four cells containing them placed in the 15 bath. In addition, a fifth 

 cell was employed to measure the conductivity of the pure solvent. 



After the cells had remained in the 15 bath for at least an hour, the 

 conductivities of the solutions were measured. Titrations of the acids 

 against the standard ammonia were made simultaneously with the 

 conductivity measurements. For this purpose 10 c.c. of the solution in 

 question were taken, by means of a pipette, from the proper measuring 

 flask in the 25 bath. A second titration in each case served to confirm 

 the results of the first. 



When the conductivities of the four solutions and of the alcohol had 

 been determined at 15, the cells were removed to the 25 bath; and 

 after the lapse of an hour measurements were made as before. The 

 same procedure was followed for the determinations at 35. 



At first thought it would seem probable that keeping the solutions in 

 the flasks at a constant temperature (25), and subjecting the solutions 

 in the cells to changes in temperature (15 to 35) would produce a 

 change in the rates of esterification. If this were true, the normalities 

 of the solutions in the cells would be different from the values obtained 

 by the titration of the solutions in the flasks, and a considerable error 

 would be introduced. It was found, however, that there was no appre- 

 ciable difference in the amount of acid present at any moment in a given 

 solution, whether the solution was kept in the 25 bath continuously 

 for 8 hours, or whether it was transferred from one bath to another 

 during this time. The reason for this is no doubt to be found in the 

 extremely slow rate at which, under the conditions of this investigation, 

 esterification takes place. 



Although it is reasonably certain that variation in the temperature 

 has no measurable effect upon the rate of esterification in alcoholic 

 solutions of the organic acids, this variation does alter to a considerable 

 extent, the volume, and therefore the concentration, of these solutions. 

 For example, a solution which has a volume of 1,000 c.c. at 25, con- 

 tracts to 989.23 c.c. when cooled to 15, and expands to 1,011.14 c.c. 

 when warmed to 35. Because of this fact a correction had to be 

 applied to the volume calculated from titration, before molecular con- 

 ductivity can be estimated at 15 and 35. This correction was made 

 in the following way: Let us suppose that the normality of a given 

 solution at 25, as determined by titration against ammonia, is N25. 

 The normality at 15, Ni 5 , would then be expressed by the ratio 



an< ^ the ^ rue volume at 15 (i. e., the number of liters which 



contain a gram molecular weight of the dissolved acid) would be the 



