﻿Liquid Films between Iridio-platinum Electrodes. 323 



In the cases of castor oil, olive oil, and paraffin there appears 

 to be a distinct and similar variation in potential gradient for 

 discharge-distances between 1 jjl and 2 fi (see fig. 4). 



The air curve is given for reference. 



Hobbs (loc. cit.) has shown that potential gradient near the 

 origin depends on the metal of which the electrodes are made, 

 every metal having a different gradient from every other. 



The electrodes used throughout these researches are iridio- 

 platinum. The gradient for this alloy is steeper (220 volts 

 per micron) than any found by Hobbs, though he found 

 platinum to have a high gradient (160 volts per micron). 



400 



Fig. 3. 



