On the Hall Effect in a Binary Electrolyte. 465 



A theoretical consideration suggested by the phenomena of 

 diffusive convection may not be uninteresting. 



As the water flows along the capillary, friction occurs and 

 heat is produced. Ultimately the dissolved salt mingles com- 

 pletely with the water. Instead of allowing the flow to occur 

 along the capillary the tap E or H might be closed. The 

 dissolved salt would then mingle completely with the water 

 without producing any flow, and the final state (assuming the 

 apparatus is thermally insulated) is exactly the same as before. 



Now the principle of the conservation of energy indicates 

 that the heat produced in the capillary plus the heat developed 

 by the mixing of the solution with water is a constant. 



Does not this indicate that the heat produced on mixing a 

 solution with water depends on how the mixing takes place ? 

 Is the matter connected with a sort of surface-tension existing 

 in the spaces between a strong and weak solution ? 



XLVII. Theory of the Hall Effect in a Binary Electrolyte. 

 By F. G. Donnan, M.A., Ph.D.* 



IN 1883 Eoiti f investigated the subject of a possible Hall 

 effect in electrolytic solutions, but failed io obtain any 

 positive result. Recently, however, the question has been 

 taken up by Bagard J, who has obtained very considerable 

 effects in aqueous solutions of zinc and copper sulphates. On 

 the other hand, negative results have been obtained by Florio §, 

 and as both Bagard and Florio maintain the correctness of 

 their experimental work, a polemic on the subject has arisen 

 between them. In this condition of affairs it seemed worth 

 while to examine what effect might be expected theoretically. 

 With this purpose in view I made the calculation contained 

 in the following pages. Subsequently I discovered that a 

 similar theory had been given by Van Everdingen, jun.|| ; but 

 as I do not arrive at quite the same results, and have considered 

 the subject somewhat more generally, it seemed to me not to 

 be needless repetition to communicate this note. 



The basis of the following calculation may be stated briefly 

 as follows. The diagram shows the directions of the primary 

 current and the magnetic field. The lines of flow of the 

 primary current are supposed to be straight and the magnetic 



* Communicated by the Physical Society : read June 24th, 189e. 



t Journ. de Physique, 1883. 



% Con^tes Rendus, vol. cxxii. pp. 77-79, and cxxiii. pp. 1270-1273 

 (1896). 



§ Nuovo Cimento, [4] vol. iv. pp. 106-111 (1898). 



j| Metingen over het Verschijnsel van Hall en de Toename van den 

 Weerstand in het Magnetisch Veld, p. 102 et seq. (Leiden, 1897). 



