116 Conductivities and Viscosities in Pure and in Mixed Solvents. 



which were weighed directly. The solution of sodium hydroxide used 

 in titration was made up approximately half -normal, from sodium 

 hydroxide from alcohol. It was preserved in an apparatus protected 

 from impurities in the air. It was standardized by titrating against a 

 standard solution of sulphuric acid of about the same strength. The 

 purest water obtainable was always used. 



MANIPULATION. 



The method in principle is a modification of that of Menschutkin and 

 Vasilieff, and later employed by A. and L. Lumiere and Barbier. In 

 order that the results should be comparable, the amount of water pres- 

 ent must be kept constant and the specific gravity of the salt solution was 

 therefore first taken; this gave the weight of 1 c.c. From analysis, 

 that part of the weight due to the anhydrous salt alone was known for 

 each cubic centimeter. This known weight of salt, subtracted from 

 the weight of 1 c.c. of solution, gave the weight due to the pure water 

 alone. This, divided into the weight of 1 c.c. of pure water at that 

 temperature, gave the amount of solution in cubic centimeters equiv- 

 alent to 1 c.c. of pure water. The amount of solution thus calculated 

 was pipetted into a 250 c.c. Jena bottle. An equivalent of 100 c.c. of 

 pure water was taken in all determinations. The bottle was suspended 

 in the constant-temperature bath. There was also placed in the bath 

 a bottle containing the anhydride and a number of small empty bottles 

 of 50 c.c. capacity. 



When all had come to the temperature of the bath, the bottle was 

 removed and 5 c.c. of the anhydride introduced. Time was reckoned 

 from when the anyhydride was first added. Solution took place imme- 

 diately on shaking, except in the case of the very concentrated solutions. 

 Equal aliquot portions were removed and placed in the small 50 c.c. 

 bottles, the whole being kept in the bath. These small bottles were 

 removed, first every 5, then every 10 minutes, and a slight known excess 

 of aniline added. This, on shaking, combines with the residual acetic 

 anhydride, precipitating acetanilide and liberating an equivalent of 

 acetic acid. 



The total amount of acetic acid was then titrated directly in the 

 bottle, using the half-normal solution of sodium hydroxide in the pres- 

 ence of phenolphthalein as indicator. Corallin had been tried, but 

 phenolphthalein was more satisfactory. The amount of acetic acid 

 due to the water alone was then calculated, using the simple formula 

 y = 2z x, where y is the amount of acetic acid due to the water alone, z is 

 the total amount of acetic acid as measured on the burette, and x is the 

 total amount of acetic acid that can be formed if all the acetic anhydride 

 has been completely hydrated. 



Two temperatures, 15 and 25, were employed. Only one concen- 

 tration of acetic anhydride was used (approximately 5 per cent), 



