XXVII. On a Relation between Ionization by Cathode Rays 

 and certain Chemical Effects. By E. Jacot, B. A. (Univ. 

 of Cape of Good Hope), B.A. (Cantab.), 1851 Exhibition 

 Research Scholar of the South African College, Cape Town ; 

 Emmanuel College, Cambridge *. 



Part I. 



AS is well known, cathode rays have certain well-marked 

 chemical effects. Up to the present time, however,, 

 little work has been done on the subject ; and this has been 

 for the most part of a purely qualitative kind. Goldstein f 

 first found that certain salts suffered discoloration by the 

 action of cathode rays. Wiedemann and G. C. Schmidt % 

 found that salts under the influence of cathode rays show 

 alkaline characteristics ; while according to Elster and 

 Geitel § such salts exhibit marked photo-electric phenomena. 

 Villard || has observed further well-marked reducing effects 

 of the rays, cupric silicate being reduced to cuprous silicate, 

 cupric oxide to metallic copper, &c. Lenard, too, has shown 

 that the passage of cathode rays through air is accompanied 

 by the formation of ozone. More recently, G. C. Schmidt % 

 has advanced the theory that in certain instances of metal 

 salts the positive valency of the metal is directly satisfied by 

 the negatively charged corpuscles of the rays. This would 

 leave the acid radicle unattached, and chemical dissociation 

 of some kind would follow. 



This theory cannot apply generally. In the general case 

 it is important to enquire more carefully into three points : 

 (1), what proportion of the so-called chemical effect of cathode 

 rays is a direct effect such as, for example, Schmidt pre- 

 sumes ; (2), what proportion is a secondary chemical effect 

 arising from purely thermal effects of the rays ; and (3), 

 what proportion is a secondary effect following from a 

 primary chemical effect on the gas or gases in the discharge- 

 tube ? Villard** insists that such residual gases in no way 

 enter into the question ; but this only refers to the case of 

 the reduction of CuO by the rays, and generalization is not 

 justified. 



The case of phosphorus is one in which the statement 

 clearly fails to apply. 



* Communicated by Prof. Sir J. J. Thomson, O.M., F.K.S. 

 t Goldstein, Wied. Ann. vol. liv. p. 371 (1895) ; vol. lx. p. 491 (1897). 

 % Wiedemann & Schmidt, Wied. Ann. vol. liv. p. 262 (1895) ; 

 vol. lxiv. p. 78 (1898). 



§ Elster & Geitel, Wied. Ann. vol. lix. p. 487 (1896). 

 |j Villard, Journ. de Phys. 3 e serie, vol. viii. p. 140 (1899). 

 H G. C. Schmidt, Ann. der Phys. vol. vii. p. 321 (1902\ 

 ** Villard, Journ. de Phys. 3 e serie, vol. viii. p. 140 (1899). 



