Mr Kleeman, The Unstable Nature of the Ion in a Gas. 263 
The Unstable Nature of the Ion in a Gas. By R. D. KLEEMAN, 
_DSe. (Adelaide), B.A., Emmanuel College. 
[Read 19 May 1913. | 
Theoretical considerations. 
THE ions in a gas are usually assumed to be stable at constant 
temperature. The writer has pointed out*, however, that it follows 
_ from thermodynamical considerations that this can by no means 
be tke case. It is shown that an ion cluster should be continually 
changing in complexity, the changes being governed by the same 
laws as chemical dissociation, namely by the laws of thermo- 
dynamics and the law of mass-action. 
Some of the principal deductions made in the paper quoted 
will be mentioned here as an introduction to the experiments 
described in this paper. If 1 denote the velocity of a free ion, 
v, that of a cluster formed by the elementary ion and a molecule, 
v, that of a cluster formed by the elementary ion and two molecules, 
and so on, and ¢), ¢), C2, --. denote respectively the concentrations 
-of the ion clusters and the elementary ions, then the average 
velocity V, the quantity measured in practice, is given by 
Va (yt 2 +2 1+ ) ! 
or daa? ieee 2s 
Oy Gs 
This equation may also be written 
Pe eT alge ET 44.) Se 
TL + Agneta He 
where H, denotes the energy of formation of a cluster 1 from an 
elementary ion and a neutral molecule at the temperature 7, 
H, the energy of formation of a cluster 2 from an elementary ion 
and two neutral molecules, and so on, and A,, A., ... are constants 
which depend only on the nature of the gas. 
From considerations based upon the kinetic theory of gases 1 
follows that the velocity of a stable cluster in a gas must depend 
on its mass, and decrease with an increase of its mass. The result 
obtained by Blanc and Wellisch+ that the velocity of an ion ina 
gas does not depend much on the nature of the molecule from 
* Proc. Camb. Phil. Soc. vol. xv1. pt. 1v. p. 285. 
+ C. R. cxuvu. July 1908, pp. 39—42 ; Proc. Roy. Soc. Ser. A, uxxx. July 31, 
1909, pp. 500—517. 
