WORK OF H. R. KREIDER. 



EXPERIMENTAL. 



This investigation was undertaken for the purpose of obtaining facts by means of 

 which the following questions might be answered : 



1. At what dilutions do the maxima in conductivity occur for various salts in 

 methyl and ethyl alcohols? 



2. Is there any relation between these maxima in conductivity for different salts in 

 different solvents? 



3. What is the magnitude of the dissociation of these 

 salts in these solvents as calculated by means of the maxima 

 in conductivity? 



4. What relation does this dissociation bear to that found 

 by means of the boiling-point method? 



APPARATUS. 



The Kohlrausch method was used. The wire was cali- 

 brated and was found to be of uniform thickness throughout. 



The cells were of the latest type used in this laboratorj^. 

 They were devised for measuring the conductivity of very 

 dilute solutions where there is great resistance. They con- 

 sist of two concentric platinum cylinders so placed one 

 within the other that the electrodes are only about 1 mm. 

 apart. (See fig. 32.) They are held together by means 

 of small drops of fusion glass placed between them. These 

 electrodes have a surface of about 48.75 square cm. One 

 of these cells had a constant as low as 2.82. The vertical 

 position of the electrodes permitted the ready escape of 

 all air bubbles, neither were they difficult to wash and dry 

 if the proper precautions were observed. These cells gave excellent results, and a 

 sharp minimum was obtained upon the bridge without difficulty. The constants 

 were determined by means of 0.01 N and 0.001 N solutions of potassium chloride. 

 These constants were frequently redetermined, but were found to change but little 

 throughout the work. 



All the apparatus was carefully calibrated. The necessary precautions concerning 

 temperature were observed. The temperature in the 25 bath was determined with 

 a sensitive thermometer calibrated against a German Reichsanstalt thermometer. 

 The bath was from time to time tested to see that there was no change in temper- 

 ature. At no time were measurements made when the temperature varied more 

 than 0.04 from that required. Careful tests were made to find the time required for 

 the temperature of the solutions within the cells, both at and 25, to reach an 



89 



Fig. 32. Type of cell em- 

 ployed in this work. 



