168 DISCUSSION OF EVIDENCE. 



would give an approximate idea of the relative solvation of the ions 

 in the two solvents in question. 



This method will be still further applied to the problem of solvation 

 in non-aqueous solvents. 



Mahin 1 studied electrolytes in ternary mixtures of the alcohol with 

 water, and obtained results of the same general character as those 

 found in binary mixtures of these solvents. He then took up work in 

 binary mixtures, one constituent being acetone. Acetone was studied 

 primarily because it is an exceptional solvent in many of its properties. 

 Substances dissolved in acetone are largely polymerized, and acetone 

 has at the same time considerable dissociating power. Furthermore, 

 acetone is a solvent with small viscosity, and it was desired to see 

 whether the relations found for solvents with larger viscosity would 

 hold here. The curve for conductivity and for fluidity were worked 

 out and the two compared. 



It was found that the product of molecular conductivity and vis- 

 cosity is nearly a constant at complete dissociation. This means that 

 for completely dissociated solutions in acetone the curves of molecular 

 conductivity are similar to those of fluidity conductivity being in- 

 versely proportional to viscosity. This relation is of interest in that 

 it holds in a solvent with such small viscosity as acetone. 



Relations such as those referred to above having been found to hold 

 in a solvent with such small viscosity as acetone, the question arose, 

 do such relations obtain in a highly viscous solvent like glycerol? 

 Glycerol not only has a very high viscosity, but is an excellent solvent, 

 and has a large dielectric constant, which means that it has consider- 

 able dissociating power. Glycerol is fairly strongly associated, which 

 also indicates considerable dissociating power. 



The first investigation in glycerol as a solvent was carried out by 

 Schmidt. 2 He measured the conductivities of solutions of certain 

 salts in glycerol, and in mixtures of glycerol with water and with methyl 

 and ethyl alcohols. The conductivities were measured at different 

 temperatures. The most striking relation noted was the enormous 

 magnitude of the temperature coefficients of conductivity of electro- 

 lytes dissolved in glycerol. This was shown to be due to the rapid 

 decrease in the viscosity of glycerol with rise in temperature. 



It was shown that where glycerol is mixed with water or the alcohols, 

 there is a breaking down of the association of each solvent by the other, 

 and a consequent diminution in the dissociating power. Solutions of 

 potassium iodide in 25 and 50 per cent mixtures of glycerol and water 

 lowered the viscosity of these solvents. This salt does not lower the 

 viscosity of glycerol, but of the mixtures. The meaning of negative 

 viscosity effects was discussed in the work of Veazey. While Schmidt 

 did not study any salt which lowers the viscosity of pure glycerol, he 



r. Chem. Journ., 41, 433 (1909); Zeit. phys. Chem., 69, 389 (1909). 

 2 Amer. Chem. Journ., 42, 37 (1909). 



