44 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



The methyl and ethyl alcohols were prepared from the purest commercial 

 preparations obtainable. Each was subjected to the same treatment. The 

 commercial alcohol was dehydrated by standing in contact with freshly burned 

 lime for several weeks. From this it was distilled, and then allowed to stand 

 over dehydrated copper sulphate for a week or more. When required for use, it 

 was distilled from the copper sulphate, small quantities of sodium being added, 

 and precautions were taken to protect the distillate from access of moisture. 



The conductivity of the methyl alcohol thus obtained was usually from 1 to 

 2 x 10~ 6 . That of the ethyl alcohol was less. 



The acetic acid used was obtained from Bender and Hobein, and was 

 designed for cryoscopic work. The amount of water contained in it was 

 determined, as suggested by Rudorf, by observation of its freezing-point. 

 Its conductivity was less than 2 x 10 ~ 6 . 



METHOD OF PREPARING THE SOLUTIONS. 



The mixtures of solvents were prepared as follows : n c. c. of alcohol, for 

 example, were diluted to, say, 100 c. c. This is designated as a mixture of 

 n per cent alcohol. Calibrated flasks were used for the dilutions, and the 

 temperature was kept within a few tenths of a degree of the temperature of 

 calibration. In making up the solutions, the exact amount of the salt in 

 question was put into a measuring-flask, and after adding a portion of the 

 solvent, the substance was dissolved and the flask filled to the mark. Here 

 also the temperature was kept under control. 



Usually, the original solutions were N/16 or N/32. From these, others were 

 made by adding the solvent to a measured portion of the solution. Where 

 the quantity to be used would be too small to be measured with reasonable 

 accuracy, one of the intermediate solutions was taken as a starting-point for 



further dilution. 



CONDUCTIVITY MEASUREMENTS 



The constants of the cells used were determined or checked at intervals of 

 a few days. For each conductivity determination, from three to seven or 

 eight different resistances were used. The values given in the tables are, 

 therefore, the mean of several determinations. Conductivities throughout 

 are expressed as molecular conductivities. 



CADMIUM IODIDE. 



The cadmium iodide used was a preparation of which a part had been 

 used by Jones and Lindsay in their work. 



Jones and Lindsay measured the conductivity of cadmium iodide in water, 

 methyl alcohol, and mixtures at 25 only. The minimum was not observed. 

 It seemed desirable, therefore, to complete the study of the compound. 



The cadmium iodide was dried by being allowed to stand in a desiccator 

 over calcium chloride for a week or more. At first the attempt was made to 



