Silent Electric Discharge 



81 



enclosed volume of gas. Before taking data with different gases, the 

 gas was blown through the apparatus for approximately one hour at 

 the rate of about 5 liters per minute. In the case of tests with the same 

 gas, 30 to 45 minutes was considered long enough to remove all traces 

 of contaminated gas. 



Figure 6 gives the results of these tests in oxygen. With gas 

 blowing through the apparatus, when determining the effect of voltage, 

 the readings were taken as rapidly as possible, the plate being grounded 

 only long enough to take a reading on the galvanometer. From the 

 curve it is seen that the current continues to increase in a negative 

 direction with an increase in voltage until the sparking potential is 



20 

 10 



30 

 15 



40 

 20 



50 

 25 



60 

 30 



70 

 35 



80 

 40 



90 KlLO-VOL-TJ 

 45 Time ~ MmuTES. 



Fis'. 6. Rectified current in oxygen. 



reached. The effect of time upon the current is very slight, as shown 

 by the other curve taken at a constant voltage of 44 kv. A charge 

 as high as 4 kv. was found to exist on the plate. 



The results with nitrogen were quite different and are given in 

 figure 7. Two sets of tests as shown by the solid and dotted curves, 

 were made upon the same day, and check fairly close. With an increase 

 in voltage the negative current increases until at 37 kv. a very definite 

 change in characteristics of the gas takes place. This is shown by 

 the scattering of the points at this portion of the curve and by the 

 sudden decided decrease of the negative current. As the voltage is 

 still further increased the current falls to zero and becomes positive at 

 the sparking potential. 



In these experiments the voltage readings were unsatisfactory due 

 to the large variation in plate voltage. A high voltage electroscope 



6—27933 



