Radiation from Gases subject to X-Rays. 695 



Duration Deflexion of Deflexion of 



of Standardizing Secondary 



Experiment. Electroscope. Electroscope. 



Air ... 31 min. 16'85 6*2 



Hydroojen . 32 min. 16*5 *95 



Hydrogen . 34 min. 17*5 *95 



Air ... 33 min. 1835 6*35 



It should, however, be remembered that when different gases 

 occupy the box, equally intense primary radiations entering 

 the box are only equally intense at the end of the box by 

 which they enter, and that the gases of higher absorption - 

 coefficient are really subjected to less intense radiation than 

 those which are more transparent. A correction must there- 

 fore be made for this loss o£ intensity due to absorption by 

 the gas contained in the chamber. Taking the path of the 

 middle primary and secondary rays as approximately giving 

 the average distance travelled in the chamber, the correction 

 necessary was that due to transmission through about 10 cms. 

 of gas. 



The absorption by the different gases was approximately 

 as follows! : — 



Air 1/5 per cent. 



Hydrogen 



Sulphuretted Hydrogen . 6 „ 



Carbon Dioxide .... 2 ,, 



Sulphur Dioxide ... 4 „ 



The following table gives the relative intensities of ionization 

 of the air in the electroscope produced by the radiation from 

 different gases subjected to equally intense primary radiation. 

 Corrections have been made for spontaneous ionization and 

 for absorption of radiation in the gas chamber. 



Assuming the penetrability of the radiations from the 

 different gases to be approximately the same — (justified 

 later) — the second column gives the relative intensity of 

 secondary radiation from the gases subjected to similar and 

 equally intense primary radiation from the bulb. The effect 

 from air has been taken as unity, the possible percentage error 

 in the case of hydrogen being very great. 



* Experiments were made on spontaneous ionization and any stray effect 

 reaching- the electroscope. Corrections Lave been made for these in the 

 above table. 



t Rutherford, Phil. Mag. [5] vol. xliii. no. 263, pp. 241-255, April L897. 



3 A 2 



