[mclennan-treleaven] residual IONISATION IN GASES 123 



The natural ionisations with the exception of that for acetylene 

 given in Column 5, it will be seen, approximate to the numbers ex- 

 pressing the relative ionisations under beta or gamma rays rather than 

 to those obtained with alpha rays. As materials such as zinc ordin- 

 arily classed as non-radio-active are not known to emit a gamma radi- 

 ation, it would seem therefore that the residual ionisation observed 

 with the different gases with the exception of acetylene could be 

 ascribed to a beta radiation probably emitted by the walls of the 

 zinc electrometer. 



It will be noted however that in the case of each gas where the 

 number expressing the residual ionisation is larger than the number 

 expressing the beta ionisation the number expressing the alpha ionisa- 

 tion is also larger. Also when the number expressing the residual 

 ionisation is smaller than the number expressing the beta ionisation 

 then the number expressing the alpha ionisation is also smaller than 

 the number expressing the beta ionisation. This indicates that 

 though the greater part of the residual ionisation in the various gases 

 may be due to beta rays a considerable part of it could be ascribed 

 to a radiation of the alpha type. If, for example, we suppose the 

 residual ionisation to be due to alpha and beta rays emitted by the 

 zinc walls of the electrometer and suppose X% of the ionisation to be 

 due to alpha rays we have for carbon dioxide the relation. 



X • 80-4 + (100-X) 156 =100X110-3 

 which gives X = 60-4. 



Applying this to the other gases we find the values for X which 

 are given in Table IV. 



Table IV. 



The values of X vary considerably and give a mean of about 

 37%. It will be seen therefore that although the method of attacking 

 the problem of seeking for an explanation of the residual ionisation 

 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 



