OF CERTAIN SALTS IN TERNARY MIXTURES. 



139 



The conception of molecular volume is opposed to the view that 

 the glycerol particle is smaller than that of acetone or water. Acetone 

 and glycerol have the same molecular volume, calculated on the basis 

 of the s:'mple molecule, i. e., 73; water has 18. Considering the associa- 

 tion factors, the molecular values are as follows: glycerol 150, acetone 

 92, water 72. From the latter consideration, glycerol has the larger 

 molecular volume, and hence should have the highest fluidity, which 

 is contrary to the facts. The error probably arises from the use of 

 the density factor in calculating molecular volume. The density of a 

 liquid is affected by both the density of the molecules and the spaces 

 between them. The kinetic molecular hypothesis states that for a gas 

 the space between the molecules is much greater than that occupied 

 by the molecules. For a liquid, the intermolecular space is less than 

 for a gas, and for a solid less than for a liquid. For liquids it seems 



125 



2(1 



15 



10 



Curve I 



Curve II 



Solvents* 2-1-1 



2-2-1 



2-1-2 



1-1-1 



1-2-1 



1-1-2 



1-2-2 



FIG. 58. Ordinates are percentages by which measured conductivity and fluidity 

 differ from the values cnlculated by averages. 



Curve I, calculated from conductivity of Rbl at 25. 

 Curve II, calculated from fluidity of solvents at 25. 



reasonable to believe that the density of the liquid gives no idea of the 

 density of the molecule or the space between them; and it is the latter 

 factor of intermolecular space as well as the size of the particle that 

 must be considered as the chief factor governing fluidity. Hence the 

 conception of molecular volume as applied to liquids is not opposed 

 to the theory that fluidity depends on the frictional surface between 

 the particles or molecular associations, and the necessary corollary 

 that the amount of frictional surface depends on the size of the par- 

 ticles. It should be noted in this connection that it is clear that the 

 intermolecular space of a gas is the most important factor affecting 

 its viscosity. It is reasonable to believe that the same factor must 

 be considered in studying the viscosity or fluidity of liquids, although 

 it is relatively less important than for gases. It is probable that the 

 present conception of molecular volume as applied to solids is approxi- 

 mately correct, since the intermolecular space may be so small that it 

 can be neglected. 



