The Diffusion of Ions Produced in Air by the Action of a Radio-Active Substance, Ultra-Violet Light and Point Discharges

J. S. Townsend
1900 Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences  
A general method of finding the rate of diffusion of ions into a gas has been described in a previous paper,* and an account was there given of the results obtained with ions produced by Itontgen rays. The present paper gives the results obtained with ions produced by a radio-active substance, by point discharges, and by ultra violet light. The principle of the method consists in calculating the rate of diffusion from observations on the loss of conductivity of a gas as it passes along metal
more » ... sses along metal tubing. The experiments were arranged so th at the loss due to diffusion should be much greater than the loss due to other causes. In order to ensure this, there are two effects which must be considered in fixing the dimensions of the tubing : the recom bination which occurs when there are both positive and negative ions present in the gas ; and the effect due to the mutual repulsion of the ions which takes place when most of the ions are charged with electricity of the same sign. I t is therefore necessary either to correct for these sources of error or to arrange the conditions of the experiments so th at the loss of conductivity due to these causes is negligible. The present paper is divided into five sections. The first section contains an investigation of the relative importance of the processes of diffusion, recombination, and mutual repulsion in causing loss of conductivity. The descriptions of apparatus, and the results of the experiments made on ions produced by a radio-active substance, by ultra-violet light, and by point discharges, are given in Sections II., 111., and IV. respectively. The conclusions to be drawn from the experiments are discussed in Section V. Section I. In the previous paper we have shown th at when a number of ions, A, are uniformly distributed throughout a gas, B, which is entering metal tubing, the ratio It, of the
doi:10.1098/rsta.1900.0028 fatcat:m44tx6dctbbs5dntgugp3dwmce