Ge) 
discharge tube, the fact that many gases in the discharge tube 
combine with the metal of the eleetrodes under the influence of the 
discharges, or, if they are compounds, break up into their components, 
is the reason that only a limited number of gases are fit for a 
research as is here described. 
Therefore hydrogen and oxygen are chosen for our research; we 
have also tried to get comparable results with carbon monoxide, 
notwithstanding the peculiarity of this gas to vanish in the discharge 
tube by the beforesaid reason. 
In order to diminish as much as possible the troubles caused by 
this process, the discharge tube was provided with a reservoir measuring 
ten times the tube itself. A copper box could be put around the 
reservoir; by heating this box with a heating spiral the gas in the 
reservoir could be heated, and so the pressure in the gas could be 
increased, if it had decreased by the selfexhausting process. 
We. studied the ionization by radiation with the three sources of 
light in the same three gases and besides in air and oxygen. The 
absorption was examined as well, and also the way in which effect 
and absorption change, if the pressure in the gas is lowered. 
The measurements were made with a CrEmMER—EDELMANN string- 
electrometer. 
One of the plates of the condensator was kept on a constant 
potential varying from 20 tot 320 Volts, the other was connected 
with the electrometer. The system condensatorplate + electrometer 
was put to earth; the earth connection could be broken quickly by 
a special device. If under the influence of the radiation the gas 
gets conductivity, the insulated plate begins to charge itself. The 
rapidity with which this happened gave the rate of the conductivity 
in the gas. The time the system needed to charge itself to a certain 
potential was measured with a stopwatch. 
The capacity of the system condensatorplate + electrometer was 
18 ¢.M. A rapidity of charge of 1 Volt per sec. corresponded with 
a current of 20 10-!? Amp. in the condensator. The exactitude 
reached in the measuring was 5°/,. 
The expectation that the research would show selective effects 
in the ionization of gases has not come true. The effect caused by 
the hydrogen “adiation as well as by the nitrogen and carbon monoxide- 
radiation prov d dependent on the pressure of the gas; whereas the 
mutual proportion of the effect on the different gases was found to 
vary with the pressure in the gas. The value of this mutual proportion 
79 
iv 
Proceedings Royal Acad. Amsterdam. Vol, XIII. 
