570 Dr. C. B. Bazzoni : Experimental Determination 



beside each curve. In A we have a Fresh charge of pnre 

 gas — ionization by collisions is seen to set in at, roughly, 

 20 volts. In B, which was run with the same gas after the 

 filament had been glowed for about an hour, the setting in 



Fig. 2. 



of ionization at 14 or 15 volts indicates the presence of 

 hydrogen, although there was no certain spectroscopic evi- 

 dence of this gas at this stage. In C we have the curve for 

 the same gas when the spectroscope showed hydrogen faintly, 

 and in D the curve when hydrogen was plain in the spectrum 

 together with a faint indication of CO. In curve C there 

 is evidence of the setting in of a second ionization above 



