f 206 J 
XXI. On the Rate of Recombination of lons in Gases. By 
GeorcE W. Watxer, V.A., A.R.C.Sc.; Fellow of Trinity 
College, Cambridge, and Lecturer in Physics in the Uni- 
versity of Glasgow *. 
i importance of this subject, at which Mr. McC tee 
has been an enthusiastic worker for some time, will 
hardly be questioned. 
In examining carefully his papers t I have observed what 
appear to me to be somewhat serious discrepancies in the 
results, which require explanation before one can accept the 
conclusions at which he arrives. 
The following criticisms are not made from lack of appre- 
ciation of the enormous experimental difficulties; for 1 was 
working in the same laboratory when the later experiments 
were made, and saw Mr. McClung very frequently. At the 
same time, the important generalizations made from the 
experiments demand for proof substantial agreement between 
theory and experiment, whatever the difficulties may be. 
We shall first recapitulate the fundamental assumptions, 
but shall assume that the reader has the papers at hand. 
If g is the rate of production of ions (in this case by Réntgen 
rays) per unit volume, and is the number of ions per unit 
volume ; then, when a steady state is reached, 
q=un,. wo 
where « is the coefficient of recombination. 
Again, when the rays are cut off, 
i eee » + . & 
where np is the number of ions per unit volume when the 
rays cease, and nm is the number per unit volume which 
remain after a time ¢. 
It is shown that 
aK. Q/N?, °°: .) Ja 
where @ is the total rate of production in the given volume, 
and N is the total number in the given volume when the 
steady state is reached, and ther efore at the instant the rays 
cease. 
K is a constant depending on the dimensions of the 
apparatus. 
We may call N; the number of ions existing in the given 
volume after a time ¢. 
* Communicated by the Author. 
t Phil. Mag. vol. i. pp. 283-305 (1902), vol. vi. pp. 655-666 (Dec. 
1903}, vol. vi. pp. 81-95 (Feb. 1904). 
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