Gaseous Mixtures by Kontgen anal Corpuscular Radiations. 847 



escaped, and if it had been absorbed it would have added 

 considerably to the ionization. Thus the most simple and 

 accurate generalization with regard to the scattered radiation 

 is contained in the statement made above, that the ionization 

 coefficients of Table IV. do not include ionization due to the 

 scattered radiation. 



The principal features to be observed in the above results 

 are these : — 



The ionization coefficient in a given gas relative to that 

 in air remains practically constant, or changes only slowly 

 with the wave-length or penetrating power of the ionizing 

 X-radiation, except when the wave-length is near and is also 

 shorter than that of a radiation characteristic of an element 

 of the ionized gas. Thus the relative ionization coefficients 

 in coal-gas, N 2 , 2 , C0 2 , N 2 change little, if at all, through 

 the range of wave-lengths used in these experiments ; those 

 in SH 2 and S0 2 rise slightly with decreased wave-length ; 

 those in SeH 2 and C 2 HoBr remain practically constant* when 

 the wave-length of the ionizing radiation is longer than that 

 of the X-radiation of series K, characteristic of Se and Br 

 respectively ; in CH 3 I the ionization coefficient rises more 

 rapidly — as does also the absorption coefficient relative to 

 that in air. When the wave-length becomes shorter than 

 that characteristic of a constituent element of the ionized 

 gas, the ionization coefficient changes in the manner described 

 in a previous paper, rising slowly, then rapidly and finally 

 approximating to a constant relative to that in air as the 

 wave-length becomes shorter. This is seen in the ionization 

 coefficients in SeH 2 , C 2 H 5 Br, and CH 3 I for radiations more 

 penetrating — of shorter wave-length — than those charac- 

 teristic of Se, Br, and I respectively. A similar variation 

 has also been found in the ionizations in Se 3 Cl 2 and SnCl 2 

 for radiations more penetrating than those of Se and Sn, 

 though only the order of magnitude of the ionizations has 

 been observed in these gases. 



It may be seen, however, that in H 2 the ionization co- 

 efficients as determined by Beatty are constant only as far 

 as the radiation characteristic of arsenic, and that the 



increase shown for Sn is of the order of magnitude that 



... 

 would be expected if H 2 had a characteristic radiation of a 



series J not hitherto observed, a series of radiations more 



penetrating than those of the K series from corresponding 



* The range of wave-length over which the ionization coefficient 

 appears constant is, however, shorter in these cases. 



