JRohtgen Radiation from Gases and Vapours. 669 



this point ; but no difference could be detected in the relative 

 amounts of secondary radiation given off by any of these 

 gases compared with air, although the hardness of the primary 

 rays wag varied as much as possible. 



It will be noticed that gases containing elements of nearly 

 the same atomic weight resemble each other in the amounts 

 of secondary radiation they give off. It seemed probable, 

 therefore, that the amount of secondary radiation was an 

 atomic property. The experiments on ammonia, nitrous 

 oxide, methyl acetate, and ethylene bromide were made with 

 a view to determining this point. 



Since equal volumes of gases at the same temperature and 

 pressure contain an equal number of molecules, it follows 

 that the relative intensities of the secondary radiation from 

 equal volumes of two gases under the same conditions is also 

 a measure of the secondary radiation per molecule for the two 

 gases. The figures given in Table I., therefore, for the relative 

 intensities of secondary radiation also measure the amount of' 

 secondary radiation per molecule in the different gases. 



The elements hydrogen, nitrogen, and oxygen were measured 

 directly, and if we assume that the secondary radiation is a 

 property of the atom and independent of its state of combi- 

 nation, we can calculate a value for carbon from the value 

 obtained for carbon dioxide, and for bromine from the mea- 

 surements on ethyl bromide. With the same assumptions we 

 can then use these numbers to calculate the relative intensities 

 of secondary radiation for ammonia,, nitrous oxide, methyl 

 acetate, and ethylene bromide. A comparison of the numbers 

 so calculated with those obtained by direct experiment 

 upon the four gases, will afford a good test of the truth of 

 the assumption made in the calculation. The figures are 

 given in Table II. 



Table II. 



Substance, 



Relative Intensities 

 of Secondary Radiation. 



Calculated. 



Observed. 



NIL, 



0-6G 

 1-53 

 2-74 

 433 



0-66 

 ■ • 1-53 

 272 

 445 



N 2 



CH 3 C0 CH 3 



CJL^Br, 







Phil. Mag. S. 6. Yol. 14. No. 83. Nov, 1907. 



2 Y 



