Rontgen Radiation from Gases and Vapours. 667 



Results. 



In all some seventeen different gases and vapours were 

 experimented upon, and the results obtained are given in 

 Table I. The first column gives the formula of the gas or 

 vapour. Column I. shows the relative amount of secondary 

 radiation given off by the gas (compared with air at the 

 same temperature and pressure) as measured by the relative 

 amounts of ionization produced. Column II. gives the 

 relative absorption of the secondary rays by a standard sheet 

 of tinfoil. Column III. shows the relative intensity of 

 secondary radiation calculated on the assumption that the 

 ionization produced in the ionization-chamber is proportional 

 to the coefficient of absorption of the rays. This correction 

 only affects five of the gases, and, as will be seen from the 

 figures, it does not at all affect the nature of the results. 

 Column IV. gives the relative densities of the gases and 

 vapours, and column V. the ratio of the intensity of secondary 

 radiation, as given in column III., to the density ; that is to 

 say, the relative amount of secondary radiation per unit mass. 



Table I. 



Substance. 



Air 



H a 



He 



NH 3 



N, 



2 



N 2 



C0 2 



S0 2 



CH 3 C0 CH 3 



cci 4 ..: 



M(CO) 4 



AsH, 



C,H 5 Br 



C.X Br 2 



SnCl 4 



CH.J 



II. 



1-00 



III. 



1-00 



012 

 O'lfi 

 066 



0-97 

 112 

 1-53 

 154 

 2-80 

 272 

 9'3 

 38-4 

 785 

 543 

 1100 

 721 

 41-5 



25 

 25 

 25 

 25 

 25 

 25 

 25 

 25 

 25 

 27 

 73 

 65 

 54 

 50 

 24 

 25 



012 



016 



0-66 



097 



1-12 



1-53 



1-54 



2-80 



272 



8-6 



81 



205 



217 



445 

 721 

 41-5 



IV. 



V. 



1-00 



1-00 



0-07 



171 



0-14 



1-14 



0-59 



112 



097 



1-00 



111 



1-00 



1-53 



100 



153 



1-00 



222 



1-26 



2-57 



1-06 



5 35 



1-61 



5-90 



1-37 



2-71 



75 6 



3-78 



57*5 



6-53 



68-2 



901 



80 



496 



8-4 



I. Secondary Radiation as measured directly by the relative ionization 

 produced. 

 II. Percentage absorption of secondary rays by a sheet of tinfoil. 



III. Relative intensity of secondary radiation as calculated from cols. I. 



& II. (See p. G64.) 



IV. Relative density. 



V. (Intensity of Secondary Radiation)/Relative Density. 



Looking through through the results, it will at once be 

 seen that the substances can be divided roughly into three 

 classes. The first class, embracing hydrogen, helium, am- 

 monia, nitrogen, oxygen, carbon dioxide, sulphur dioxide, and 



