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Societies and Academies

Nature volume 88, pages 469471 (01 February 1912) | Download Citation



LONDON. Royal Society, January 2. Sir Archibald Geikie, K.C.B. president, in the chair. Prof. J. S. Townsend: Determination of the coefficient of interdiffusion of gases and the velocity of ions under an electric force, in terms of the mean free paths. A method is described by which an expression for the rate of interdiffusion of gases may be easily found, either on the ordinary supposition that the effect of a collision makes all subsequent directions of motion of the molecules equally probable, or without specifying in any way the effect of a collision. Similar expressions are found for the velocity of ions under electric forces. In all cases the rate of diffusion of the ions is of the form K = kLV, and the velocity under the electric force u=L does not, in general, represent the mean free path, but it has the same meaning in both expressions, so that when an ion is moving under the action of a force and also by the process of diffusion its velocity is given by the equation

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