122 CONDUCTICITY AND VISCOSITY 



The acetone was dried over calcium chloride for at least a week before 

 using and was then redistilled several times immediately before making 

 up the mixed solvents. It had a mean specific gravity of 0.787 at 25, 

 and a specific conductivity of about 4X10~ 7 at that temperature. 



The conductivity water was obtained by the method of Jones, 

 McKay, and Schmidt, and had a mean specific conductivity of 

 1.5Xl(T 6 at 25. 



The mixed solvents were prepared by mixing one or two parts of each 

 of the above components with varying proportions of the other two. 

 Seven such combinations proved to be possible, and were prepared for 

 solvents in one-liter quantities immediately before using. 



The specific data relating to each solvent are to be found in table 33. 



SALTS. 



The rubidium and ammonium salts were all carefully recrystallized 

 from conductivity water, precipitated and washed with absolute 

 alcohol, then dried first in the steam oven, and finally pulverized and 

 heated in an air-bath at the most favorable temperature for the salt 

 in question. By this procedure, products of an exceptional purity were 

 obtained, and even in the case of ammonium iodide the concentrated 

 solutions became only slightly tinted after standing. 



SOLUTIONS. 



All solutions were made up as described by Davis and Hughes; the 

 concentrated solutions by direct weighing, the others by successive 

 dilutions. All operations were carried out at 20. 



PROCEDURE. 



Measurements both of conductivity and viscosity were made at 15, 

 25, and 35. The data were calculated in the usual way, tables of 

 constants and the use of a calculating machine greatly facilitating the 

 operation. The viscosity coefficients were obtained from the formula 



7 st 



where TJ O , s , and t Q are the viscosity, density, and time of flow of pure 

 water, and 77, s, and t the corresponding values for the liquid in question 

 in any given viscosimeter. 



Fluidity, represented by <f>, is equal to - The temperature coeffi- 



^7 



cients in conductivity units represent the actual increase in molecular 

 conductivity per degree rise in temperature. 



Per cent temperature coefficients, both of conductivity and fluidity, 

 were calculated from the formula: 



Temp, coeff. of (, or ) = -?- . ("o 



