SOLVENTS. 



25 



The glass tubes carrying the electrodes were shoved 

 through thin rubber tubes, and then inserted into the 

 glass tubes in the cap. Sealing wax was then run 

 over the outside of the joint. 



The zero-bath was prepared as follows: A large 

 glass battery-jar was filled with pure, finely crushed 

 ice, and moistened with distilled water. This was 

 placed in a water-bath, the space between the two 

 being filled with finely crushed ice. By this means 

 it was possible to keep a cell within 0.02 of zero 

 for hours. The 25 bath was of the ordinary form 

 and was stirred by means of a small hot-air engine. 



The thermometers used were graduated to 0.04 

 and were carefully calibrated. The burettes and 

 flasks were also carefully calibrated. 



SOLVENTS. 



WATER. 



FIG. 1. 



All the water used in this work was purified as 

 follows: Ordinary distilled water was first distilled 



from acidified potassium dichromate. This water was redistilled from 

 potassium dichromate acidified with sulphuric acid, and then from barium 

 hydroxide. The water purified in this way had a conductivity of never more 

 than 2 x 10~ 6 , and sometimes as low as 0.8 x 10 ~ 6 . 



METHYL ALCOHOL. 



The methyl alcohol used was the best commercial article that could be 

 obtained. It was first boiled with calcium oxide, then distilled and allowed 

 to stand over anhydrous copper sulphate for weeks. Before use it was dis- 

 tilled from the copper sulphate and then from sodium. None of the alcohol 

 used in making up the solutions in absolute alcohol had been distilled from 

 sodium more than twenty-four hours before use. It had a conductivity of 

 about 2.3 x 10~ 6 . 



ETHYL ALCOHOL. 



The ethyl alcohol was the best obtainable article, and was purified in the 

 same manner as the methyl alcohol. Its conductivity had a mean value 

 of 2xlO- 7 . 



PROPYL ALCOHOL. 



The propyl alcohol was Kahlbaum's best, and before use was distilled 

 from anhydrous copper sulphate and sodium. It had a conductivity of 

 0.8 X 10~ 7 " 



