ON ENERGY OF EONTGEN AND BECQUEREL RAYS, ETC. 
49 
This value is a little higher than in the case of air. The measured amount of io, 
the current in carbon dioxide, was somewhat less than the maximum, since the 
electromotive force applied was not sufficient to move all the ions to the plates before 
recombination. A correction for this would make the values for air and carbon 
dioxide more nea,rly equal. 
Taking the value 1’53, found by J. J. Thomsox,"^ for the relative ionization in 
carbonic acid and air, the ionic energies are nearly the same. 
The results for air and carbon dioxide show that the energy required to produce 
ions in the two gases is not very different. The results of a previous paperf showed 
that the absorption of X rays in gases was roughly proportional to the ionization 
produced. From this it follows that the energy required to produce ions in the 
gases examined was, roughly, the same. 
The results obtained with uranium ]‘adiation;j; showed that the total number of 
ions produced by complete absorption of the radiation in air, oxygen, hydrogen, 
carbonic acid gas, hydrochloric acid gas, and ammonia were approximately the same. 
The results in that case were more readily olffained as the radiation Avas almost 
completely absorbed in a few centims. of the gas, and the maximum current through 
the gas was a measure of the total numljer of ions produced. 
The recent results of McLexxan§ also point strongly in the same direction. 
In his experiments, cathode rays were passed out of the discharge tube into another 
vessel, and the maximum current produced by the cathode rays Avas found for 
different gases. Using a constant supply of cathode rays, the current, ?'.c., the 
total number of ions produced, was independent of the nature of the gas (proAuded 
the pressure of the gas Avas adjusted to give the same absorption of the rays in eacli 
case). The gases examined Avere air, hydrogen, oxygen, nitrogen, caiFonic acid, 
nitrous oxide, and the total number of ions produced in them Avas nearly the same. 
Assuming that the same proportion of energy of tlie cathode rays was used up 
in producing ions in the gases, it follows that the energy required to produce an ion 
in all the gases is the same. 
The results on the ionization of different gases by the agency of Rontgen, Becquerel, 
and cathode rays all strongly point to the conclusion that the same energy is required 
to produce an ion whatever the gas. 
Variation of Ionic Energy with Pressure. 
It has been shoAvn earlier in the paper that from half an atmosphere to three 
atmospheres’ pressure the absorption is proportional to the pressure. A special 
* J. J. Thomson, ‘ Camb. Phil. Soc. Proc.,’ a'oI. 10, Part I. 
t E. Rutherford, ‘Phil. Mag.,’ April, 1897. 
I E. Rutherford, ‘ Phil. Mag.,’ January, 1899. 
§ ‘Roy. Soc. Proc.,’ 1900; ‘Phil. Trans.,’ A, a^oI, 195. 
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