266 Mr Kleeman, The Unstable Nature of the Ion in a Gas. 
K 
of ions drawn through the gauze. It will be seen that the curve 
B is nearer to the zero than the curve A, as required. But the 
difference in position is much greater than warranted by the 
increase of the initial ionisation on bringing the radium near 
the chamber, which is very small since the curves almost coincide 
for small fields. It follows therefore that only a small proportion 
of the ions drawn through the gauze are in a state fit for the — 
production of ions by collision, or the proportion of free ions to 
clusters is small in a number of ions in equilibrium in ether. 
The following vapours were also examined in this way: ethyl 
propionate, methyl butyrate, acetylene, hydrogen, oxygen, nitrous 
oxide, carbon dioxide, air, carbon tetrachloride, ethyl chloride, 
chloroform, pentane, benzene, hexane, aldehyde, methyl formate, 
Leak 
200 400 600 800 1000 1200 1400 
Volts per cm. 
Fig. 2. 
methyl bromide, methyl iodide, ethyl bromide, ethyl iodide, and 
carbon disulphide. The results obtained could to a certain extent 
be compared with one another, as will be explained. From the 
theory of clustering referred to at the beginning of the paper it 
follows that the number of free ions to clusters is independent of 
the pressure of the gas. The writer* has shown that the relative 
ionisation in gases whose molecules do not contain atoms of higher 
atomic weight than that of the chlorine atom is the same for v 
and a rays, and in the case of the other gases the ionisation is 
greater in the latter case than in the former, but the ratio is 
always less than two. The initial numbers of free ions introduced 
by the y and a rays respectively are therefore always proportional 
* Proc. Roy. Soc. A, vol. uxx1x. p. 220, 1907. 
