426 Prof. J. 0. McLennan and Mr. C. L. Treleaven on 



Table IV. 



Gas. 



X = percentage ionization due to alpha rays. 





60*4 per cent. 



23-4 „ „ 



14-4 „ „ 



49-2 „ „ mean =36 "9 per cent. 



Hydrogen 



Ethylene 



Nitrous oxide 





The values of X vary considerably and give a mean of 

 about 37 per cent. It will be seen, therefore, that although 

 the method of attacking the problem of seeking for an 

 explanation of the residual ionization in gases cannot at all 

 be considered an exact one, still it appears to be one of the 

 very few methods available, and from the results obtained it 

 goes to show that the residual ionization observed in the 

 gases tested, with the exception of acetylene, was probably 

 due to a radiation emitted by the zinc walls of the electro- 

 meter, which was partly of the alpha, partly of the beta, 

 and possibly partly of the gamma type, with roughly about 

 37 per cent, of the ionization due to alpha rays. 



Considering the case of acetylene we see that in the second 

 investigation, as in the first, an exceedingly high value was 

 obtained for both the natural and the residual ionization in 

 this gas. From Table III. it will be seen that under alpha 

 and beta rays it was ionized to about the same extent as 

 ethylene, and as the residual ionization in ethylene was 

 6*32 ions per c.c. per second, while in acetylene it was 

 27 ions per c.c. per second, it is clear that the high residual 

 ionization in the latter gas cannot be accounted for by 

 an alpha and beta radiation from the walls of the 

 electrometer. 



It would look rather as if the ionization in this case was 

 either really spontaneous or else that it was due to some 

 chemical action set up in the electrometer owing to the 

 presence of some gaseous impurity. 



To test the latter hypothesis an experiment was made with 

 hydrogen prepared by adding water to commercial calcium 

 hydride. The manner in which the hydrogen is produced 

 in this case is very similar to that in which acetylene is 

 obtained from calcium carbide, and it was thought that if a 

 gaseous impurity were present in the acetylene the same 

 impurity might be expected to be present in the hydrogen 



