Ionization of Gases and the Absorption of Rontgen Bays. 313 
•electrons produced by the X-rays lose their energy by successive impacts- 
Each impact may, or may not, produce a pair of ions, although the 
average number of pairs of ions produced per electron will be constant 
for the same gas under the same conditions. Bohr has shown that the 
energy lost by such an impact giving rise to a pair of ions must at least 
be equal to the kinetic energy of the electron in its orbit before it was 
Jm 
removed by the impact of the corpuscular ray and = , where n is the orbital 
frequency and h is Planck's constant. The corpuscular co-efficient (k) for 
Hg alone is 102 and for alone is 110, yet that for SHg is 133 and for 
SOo is 96, identical corpuscles being employed in all cases. On the face 
of it, it is difficult enough to account for the similarity of the numbers 
102 and 96 for two such different gases as H2 and SO.,, except by assuming 
Table I. 
Gas. 
Total ionization 
= kM. 
Ionization by a 
corpuscle = k. 
Number of corpuscles 
= M. 
(numbers relative.) 
Air 
0.2 
CO., 
SHo 
so; 
1 
•001* 
•715 
(1^38 
U-32 
1^40 
14-7 
11-7 
100 
102 
93 
110 
102 
133 
96 
1 
•001 
•770 
(1-25 
11- 20 
1-37 
1105 
12- 2 
Ionization by Cu X-rays except Oxygen, 1*32 is the mean value of the ionization 
for elements varying from Fe to Sb. 
that the mean kinetic energy of the H3 electrons equals that of the 
SO2 electrons, a result which does not agree with Bohr's conclusions. 
Again, if the loss of energy of the corpuscle in its passage through the 
atom is equal to one quantum of radiation from the atom, the quantum for 
hydrogen is less than it is for oxygen, and we should expect a greater 
number of pairs of ions to be produced in hydrogen than in oxygen. 
Apparently the corpuscle on the average loses less energy per impact with an 
SH2 molecule than it does per impact with an SO2 molecule. The state 
of combination of the atoms affects the energy dissipated per impact in 
the form of radiation, and apparently it is the number of quanta of 
radiation that is affected, but not the frequency, the " hardness " of the 
secondary radiation being found to be independent of the state of chemical 
combination. 
It will be apparent that the ionization in a gas is the product of two 
* Shearer, Phil. Mag., xxx, p. 644. 
