﻿Ionization produced by Carbon at High Temperatures. 193 



from 0*1 to 0*001 mm. the influence of the ionization of the 

 surrounding gas was supposed to be eliminated, and the 

 currents produced were considered to be due to the liberation 

 of corpuscles from the carbon. 



It had previously been stated by M'Clelland * that the 

 negative ionization from metals is independent of the pressure 

 over a range from 0*04 to 0*004 mm. The ionization 

 currents found by Richardson, and attributed to the liberation 

 of corpuscles, ranged from 10~ 8 to 2 amps, per square cm. 

 of carbon, according to the temperature. A formula which 

 had been deduced to show the relation between ionization 

 and temperature was found to be in good agreement with the 



_ b 



experimental results. In this equation 1 = K6* e where 

 I denotes the ionization, A and b are constants, and 6 is the 

 absolute temperature. In the case of carbon, Richardson 

 found that A = 10 3i and 6 = 9*5 x 10 4 . According to this 

 formula, the ionization will increase at a rate which at 

 1500° is about equal to the 50th power of the temperature. 

 As is well known, there are no means of precisely estimating 

 the temperature of thin filaments. 



F. Deininger f investigated the ionization from carbon 

 and various metals alone, and in presence of lime, and 

 concluded that Richardson's formula applied in every case 



up to 1450°. Thus log I — -J log 6 was plotted against ^ 10 4 , 



and found to give a straight line. No mention is made of 

 the pressure. 



H. A. Wilson J investigated the ionization from platinum 

 and found that this varied very much with the previous 

 treatment of the metal. Thus, by long continued heating, 

 or else by previously submitting to the action of nitric 

 acid, the ionization was largely diminished. He concluded 

 that the ionization from platinum is independent of 

 the pressure from 0*2 to 0*001 mm., but that a reduction 

 to 250^00 °^ ^he original ionization is produced by removing 

 the last traces of occluded hydrogen. Wilson states that 

 in some experiments carried out with carbon he confirmed 

 the general results of Richardson. 



The present work was undertaken with a view to examine 

 the ionization from carbon at temperatures which were more 



* Proc. Cambr. Phil. Soc. x. p. 241 ; xi. p. 299. 

 t Ber. deutsch.physik. GeseU. (1907) ix. p. 674. 

 \ Phil. Trans. (1904) A. ccii. p. 248. 



Phil Mag. S. G. Vol. 23. No. 133. Jan, 1912, 



