DISCUSSION OF EVIDENCE. 169 



found that the effect of the salt on the viscosity of pure glycerol was 

 inversely as the molecular volume or atomic volumes of the constitu- 

 ents of the salt. This was in keeping with the explanation offered by 

 Jones and Veazey to account for the changes in the viscosity of the 

 solvent by the dissolved substance. A comparison of the conduc- 

 tivity and fluidity curves show r s that the two run nearly parallel. 

 Although glycerol has about 1,000 times the viscosity of methyl alcohol, 

 yet, from the work of Schmidt, the same general relations obtain here 

 that hold for the far less viscous solvents. 



The work of Schmidt was continued by Guy. 1 He worked with a 

 much larger number of salts, and over the temperature range 25 to 

 75. He studied not only solutions in glycerol, but in mixtures of 

 glycerol with water, with methyl, and with ethyl alcohols. 



Guy found also enormous temperature coefficients of conductivity. 

 This may be due to either of two causes: a change in dissociation with 

 rise in temperature, or a change in the velocity of the ions. We know 

 the order of magnitude of the change in dissociation with rise in tem- 

 perature, and it is small. The chief cause of the large temperature 

 coefficients of conductivity in glycerol is, then, an increase in the 

 velocities with which the ions move. As we have seen, this may be 

 due to a decrease in the viscosity of the solvent with rise in temperature, 

 or may be caused by a breaking down of complex solvates about the ions. 



While the viscosity of glycerol increases rapidly with rise in tem- 

 perature, this alone would not account for the magnitude of the temper- 

 ature coefficients of conductivity of glycerol solutions. There seems 

 to be good evidence for the formation of glycerolates in solutions in 

 glycerol. The temperature coefficients of conductivity in glycerol are 

 greater at high than at low dilution. Jones has pointed out that this 

 would be expected from the solvate theory. The more dilute the 

 solution the more complex the solvate; the more complex the solvate 

 the greater the change in its complexity with rise in temperature. 



Further, salts of calcium, strontium, and barium have larger tem- 

 perature coefficients of conductivity than those of sodium, potassium, 

 and ammonium. The former are strongly hydrated, the latter weakly 

 hydrated substances. It would seem that the former are more strongly 

 glycerolated than the latter. Salts which have approximately the 

 same hydrating power have temperature coefficients of conductivity 

 in glycerol of the same order of magnitude, indicating the same order 

 of magnitude of glycerolation. Work in the mixed solvents indicates 

 that water diminishes the association of glycerol. 



Solutions of salts in glycerol have in general greater viscosity than 

 pure glycerol. Guy, however, found marked exceptions to this rela- 

 tion. Salts of rubidium lowered the viscosity of glycerol. Ammonium 

 bromide and iodide also lowered the viscosity of this solvent. That 



lAjner. Chem. Journ., 46, 131 (1911). 



