CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



INTRODUCTION. 



The earlier work in physical chemistry had to deal almost exclusively 

 with aqueous solutions. This was due to the fact that water is by far the 

 most universal solvent. It dissolves a much larger number of substances 

 than any other known liquid. Further, water has greater power to break 

 molecules down into ions than any other common solvent. For these reasons 

 water is the most important solvent chemically; indeed, chemistry is largely 

 a science of aqueous solutions. 



Again, water, of all the common solvents, is the most easily obtained, and 

 in a fair degree of purity. These are some of the reasons why solutions in 

 water as the solvent were studied first. 



During the last few years, the measurement of dissociation has been extended, 

 to a greater or less extent, to solutions in many solvents, both inorganic and or- 

 ganic, and in several cases interesting and important results have been obtained. 



The study of non-aqueous solutions has led to a comparison of the dis- 

 sociating power of the various solvents, and this in turn has given rise to 

 several generalizations which attempt to connect dissociating power with 

 other physical and chemical properties of solvents. 



J. J. Thomson l and Nernst 2 have sought to connect the dissociating power 

 of a solvent with its dielectric constant. Nernst says: 



The greater the dielectric constant of a medium, the greater becomes its electrolytic 

 dissociation of dissolved substances under exactly similar conditions. 



J. J. Thomson, after showing that molecules condensed on the surface of 

 a conducting sphere will be completely dissociated, goes on to say : 



The same effect would be produced by a substance possessing a very large specific 

 inductive capacity. Since water is such a substance it follows, if we accept the view 

 that the forces between the atoms are electrical in their origin, that when the molecules 

 of a substance are in solution, the forces between them are very much less than they are 

 when the molecule is free and in the gaseous state. 



Briihl 3 showed that while certain organic bodies, as the oximes and the 

 alcohols, exist in a polymerized state when dissolved in hydrocarbons, 

 chloroform, or carbon disulphide, the molecular complexes are more or less 

 broken down in aqueous solution, and to a less extent in alcohols, ethers, 

 esters, ketones, and phenols. All of these also exert more or less dissociating 

 power. According to his theory of the tetravalence of oxygen they are 



'Phil. Mag., 36, 320 (1893). 2 Ztschr. phys. Chem., 13, 531 (1894). 



3 Ibid., 18, 514 (1895); 27, 319 (1898); 30, 1 (1899). Ber. d. chem. GeselL, 28, 2847, 

 2866 (1895); 30, 163 (1897). 



