174 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



the use of N/50 and N/500 solutions of potassium chloride. The value used 

 for N/50 potassium chloride at 25 was 129.7. The value for N/500 potassium 

 chloride was determined every time a fresh solution of it was prepared, by 

 first determining the cell constants of several cells with N/50 potassium chlo- 

 ride, and then using these cells to determine the value for N/500 potassium 

 chloride. The cell constants were checked at frequent intervals. After use 

 the cells were repeatedly rinsed with distilled water, and when not in use the 

 cells were filled with distilled water. The cells before use were rinsed with 

 water and then with absolute alcohol, and allowed to dry at ordinary tempera- 

 tures. 



The use of ether in drying the cells was avoided, since it is likely to con- 

 tain small amounts of non-volatile substances. 



In table 78 v is the number of liters of solvent that contain 1 gram- 

 molecular weight of the salt; ^0 is the molecular conductivity at 0, 

 and /v25 is the molecular conductivity at 25. 



The temperature coefficients were calculated according to the Kohlrausch 

 formula, and, if multiplied by 100, would express the temperature coefficients 

 in percentage of conductivity units. The Kohlrausch formula as it was 



COBALT NITRATE. 



A number of methods were used in an attempt to obtain perfectly anhy- 

 drous cobalt nitrate, but without success; and since it is absolutely neces- 

 sary to have the salt completely anhydrous for this work, this salt had to be 

 abandoned. 



The most nearly successful attempt to dehydrate the salt was carried out as 

 follows : The salt was heated several days to dryness on a water-bath, and 

 was then recrystallized several times from strong nitric acid. The crystals 

 were then washed with anhydrous ligroine to free them from the acid. They 

 were then filtered and drained by the aid of a suction-pump, the funnel con- 

 taining the crystals being carefully protected from the moisture of the air. 

 The salt was then heated for a day or two in a current of dry air at a tempera- 

 ture of from 50 to 60. An analysis of the sample thus obtained, for metallic 

 cobalt by the electrolytic method, showed that the salt still contained a con- 

 siderable amount of water. 



COPPER CHLORIDE. 



The copper chloride used in this work was prepared as follows : Kahlbaum's 

 pure crystallized copper chloride was recrystallized from dilute hydrochloric 

 acid to free it from small quantities of basic salt. These crystals were then 



