IOWA ACADEMY OF SCIENCES. 129 



11 was taken as the mother solution, and the remaining 

 solutions prepared in a similar manner from it. Dupli- 

 cates of every solution were made and their conductivities 

 determined. All pipettes and measuring flasks used were 

 carefully calibrated by the method of Morse and Blalock.* 

 In measuring the conductivity of the solutions two cells 

 were used; one with the electrodes removed some distance 

 from one another for the more concentrated solutions, and 

 the other with the plates close together for the more dilute 

 solutions. In this way greater accuracy was possible. 



The Ostwald modification of the Kohlrausch method was 

 used. The cells were carefully standardized with -g- potas- 

 sium chloride (Mu V=129.7 at 25°) at the beginning of each 

 seres of measurements. The water used in the solutions 

 was prepared by the method of purifying devised by Jones 

 and MacKayf . 



Solutions of the constituents were prepared and meas- 

 ured in the same way as the double salts. 



In tables V is the volume of the solution in litres which 

 contain a gram molecular weight of the electrolyte. Mu V 

 is the molecular conductivity at volume M . All the con- 

 ductivity measurements were made at a temperature of 

 25 . 



A solution of the double salts, sodium cadmium bromide, 

 was prepared and standardized by determining the amount 

 of cadmium in a known volume of the solution. From 

 the standarized solution all the remaining dilutions were 

 prepared. 



* The American Chemical Journal, xvi, 479. 

 + The American Chemical Journal, xix, 91. 



