210 Charges on Ions in Gases. 



at high pressures (about atmospheric pressure) by Mr. ft. T. 

 Beatty * and Mr. C. T. ft. Wilson f. Mr. Beatty finds experi- 

 mentally that when Rontgen rays pass through some gases 

 a large part of the ionization is due to corpuscular rays,, 

 and that the fraction of the whole number of ions thus pro- 

 duced depends on the kind of primary rays that are used. 

 Practically the same conclusion is arrived at by Mr. C. T. ft. 

 Wilson, in which he finds even with 7-rays that the ions in 

 a gas are produced along fine lines traversing the gas in -all 

 directions — the tracks of /3 particles from the walls of the 

 vessel. 



The principal conclusions of the various experiments on 

 these subjects are, it seems to me, much more in harmony 

 than a superficial examination of the results would lead one 

 to expect. 



Professor Millikan's recent results, in which he found that 

 none or very few positive ions with double charges were 

 caught on the small drop that he had under observation, have 

 led him to believe that no such positive ions are generated in 

 the gas. It seems to me that, before such a definite conclusion 

 can be arrived at, it would be necessary to know what pro- 

 portion of the ions that are caught could be expected to be 

 ions with double charges. If only nine or ten per cent, of 

 the positive ions have double charges the question then arises^ 

 whether doubly charged ions are as likely to come into 

 contact and adhere to the small drop as the smaller ions with 

 a single positive charge. It would be rather difficult to 

 decide what would happen with the different kinds of ions, 

 but it is reasonable to suppose that doubly charged ions 

 would have around them a larger group of molecules than the 

 singly charged ions ; and if, as Franck and Westphal found,, 

 their rate of diffusion is about half that of the smaller ions, their 

 velocity of agitation would be proportionally small, so that 

 they trace out a path through the molecules of the gas that 

 would be half that of ions with single charges before they are- 

 brought up to the electrode. Under these circumstances 

 any one of the doubly charged ions would be less likely than 

 an ion with a single charge to strike a small object in the gas. 

 Also the conditions under which ions with different masses 

 would adhere to the drop are not necessarily the same. It is 

 interesting to note in this connexion that the experiments have 

 shown that negatives are caught more easily than positives. 



* "Ionization of Heavy Gases by X-Rays," Proceedings of Koyal 

 Society, A. vol. lxxxy. June 1911. 



•j- "On a Method of making visible the Paths of Ionizing Particles 

 through a Gas," Proceedings of Royal Society, A. vol. lxxxv. June 1911. 



