﻿Ionization produced by Carbon at High Temperatures. 197 



carbon, a reaction which would proceed to a certain equi- 

 librium value at any given temperature, or else it is due to 

 oxvgen resulting from slight dissociation of the oxides in 

 the glass, though the temperature of the latter, of course, 

 never reached the softening point. 



Measurement of Ionization. — A potential difference of 

 about 330 volts was applied between E and A (fig. 1) except 

 where otherwise stated, and the latter made negative. In 

 this way it was hoped to collect most of the ions coming 

 from the carbon. At this voltage, however, the original 

 ionization must have been increased by collision, as only 

 about half the current was obtained on using 200 volts. It 

 was found that by placing the graphite rod E at 11 cm. 

 instead of 4*8 cm. from the carbon, a fall in the ionization 

 current of not more than one-fifth was caused. The results 

 obtained when using impure carbon are shown in the form 



•S -3 •* >S 



/°f?£SSURE //V MMS. 



of curves in fig. 2, where the ordinafces denote the ionization 

 current in milliainpcres per 1 sq. cm. surface of carbon and 



