There are several interesting results in connection with molecular physics which can be obtained from the coefficients of diffusion of ions into gases. From determinations of these coefficients we are enabled to find the number of molecules in a given volume of a gas, and to compare the charge on an ion in a conducting gas with the charge on a hydrogen ion in a liquid electrolyte. In the present paper the principles which are involved in the theory of the interdiffusion of gases are applied to the diffusion of ions produced in a gas by the action of Röntgen rays.
