viii THE GENERAL PHYSICAL PROPERTIES OF ALBUMINS 255 



may undergo an analogous change. In the light of Brunt's conception, 

 and taking also into consideration that even pure water is partially 

 dissociated, and possesses a high dielectric constant, 1 the following 

 possibilities suggest themselves : 



1. The substance and the solvent, by mutually diffusing into one 

 another, form mixtures without the solute undergoing electrical dis- 

 sociation. This happens, for example, if sugar or mercuric cyanide 

 dissolve in water, and also happens as the preliminary step in all cases 

 where electrolytes dissolve; but in the case of electrolytes the primary 

 'passing into solution' is followed by a secondary chemical dissocia- 

 tion as described below. 



The author believes, when diffusion takes place, that the solvent 

 has one electrical charge, while the solute has the opposite charge. 

 The mixture being a binary system, it is impossible for an electrical 

 current to pass through it, as this would mean moving both the 

 solvent and the solute. 2 



2. The substance undergoes in the solvent electrolytic dissociation, 

 as in the case of electrolytes or salts containing radicals capable of 

 giving rise to strong positive ions or kations, and to strong negative 

 ions or anions. Thus in the case of common salt, sodium becomes + , 

 while chlorine becomes - : 



NaCl + zH 2 J Na + Cl' + H 2 0. 



In this case an electrical current passes through the mixture of 

 solvent and solute, because we are dealing with a ternary system con- 

 sisting of a medium, the solvent, in which both negative and positive 

 ions, derived from the solute, are freely movable. 



3. The substance, being composed of a potential, strong kation and 

 a potential, feeble anion, or vice versa, undergoes hydrolysis, which 

 means that the weaker ion of the salt is replaced by a stronger ion 

 derived from the solvent. If the solvent is water, and if the weaker 

 ion of the solute is electro-positive, its place is taken by the acid 



1 A dielectricon is a substance without any electrical charge of its own, but capable 

 of having an electrical charge induced in it. According to Coehn droplets having the 

 smaller dielectrical constant become electro-negative towards media with higher dielec- 

 trical constants, in a mixture consisting of two non-miscible fluids. According to Drude 

 (Drude, Zeit. f. physik. Chem. 23. 308 (1897)) the dielectrical constants for the follow- 

 ing substances are : Water 80*9, glycerine 56 '2, methyl-alcohol 32'6, ethyl-alcohol 25'S, 

 prophyl-alcohol 22 '8, acetone 21'8, amyl-alcohol 16 '0, aldehyde 18'6, acetic acid 9*7. 

 These substances are all electro-positive towards glass, while the following bodies are 

 electro-negative : Chloroform, ethyl-ether, valerianic acid, carbon disulphide, xylol, 

 toluol, benzol, oil of turpentine. 



2 Mann, Physiological Histology, 1902, p. 45. See also in this book, pp. 268 and 

 279, Tinder Billitzer. 



