the Electrical Conduction produced by it. 



137 



the rate of movement of the electrometer-needle was pro- 

 portional to the total number of ions produced in the gas. 

 The following were some of the results obtained, the rate of 

 leak due to air being taken as 100. 



Gas. 



Total 

 Ionization. 



Air 



100 

 95 

 106 

 96 

 111 

 102 

 101 



H vdroffen 



1 g 







Hydrochloric Acid Gas ... 





The results for hydrochloric acid and ammonia are only 

 approximate, for it was found that both gases slightly altered 

 the radiation emitted by the uranium oxide. For example, 

 before the introduction of the gas the rate of leak due to air 

 was found to be 100 divisions in 69 sec; after the introduction 

 of hydrochloric acid 100 divisions in 72 sec. ; and with air 

 again after the gas was removed 100 divisions in 74 sec. 



The rate of leak is greatest in coal-gas and least in hydro- 

 gen, but all the gases tried show roughly the same amount 

 of ionization as air. In the case considered both kinds of 

 radiation emitted by uranium are producing ionization in 

 the gas. By covering over the uranium oxide with a few 

 layers of thin tinfoil it was found that, for the arrangement 

 used, the rate of leak due to the penetrating ray was small in 

 comparison with the rate of leak due to the a, radiation. 



The effect of diminution of the pressure on the rate of leak 

 for air, hydrogen, and carbonic acid is shown in fig. 7, 

 where the abscissae represent pressure and the ordinates rate 

 of leak. In the case of air and carbonic acid it was found 

 that the rate of leak slightly increased at first with diminu- 

 tion of pressure. This was ascribed to the fact that even 

 with 800 volts acting between the uranium and the surround- 

 ing conductor the saturation for atmospheric pressure was 

 not complete. It will be observed that the rate of leak in 

 air remains practically constant down to a pressure of 

 400 mm., and for carbonic acid down to a pressure of 

 200 mm. In hydrogen, however, the change of rate of leak 

 with pressure is more rapid, and shows that all the radiation 



