FLUIDITY .AND THE CHEMICAL COMPOSITION

113

Comparison of Fluidities.—We have already given reasons for
believing that if liquids were completely unassociated and
expanded in a linear manner with the temperature, the fluidity-
temperature curves would be straight lines. To compare a
family of curves which are straight lines is a simpler task than
the comparison of a family of hyperbolas, hence it seems a justi-

Stf 100°

FIG. 41.—The fluidities of vari-
ous hydrocarbons at different
temperatures and extrapolated
to their boiling temperatures.
4. Pentane; 5. Isopentane; 6.
Hexane; 7. Isohexane; 8. Hep-
tane; 9. Isoheptane; 10. Octane;
11. Trimethylethylene; 12. Iso-
prene; 13. Diallyl; 56. Benzene;
57. Toluene; 58. Ethyl benzene;
59'. (0)-Xylene 60, (w)-Xylene;
61. (p)-Xylene.

i,

//

f

,'A

y,

FIG. 42.—The fluidities of various
ethers and acid anhydrides at differ-
ent temperatures and extrapolated
to their boiling temperatures. 53.
Acetic anhydride; 54. Propionic
anhydride; 55. Diethyl ether; 83.
Methyl propyl ether; 84. Ethyl
propyl ether; 85. Dipropyl ether;
86. Methylisobutyl ether; 87.
Ethylisobutyl ether.

fiable expectation that we may be able to find simpler relations
by a suitable comparison of fluidities. Before deciding on a
basis of comparison let us inspect the fluidity-temperature
curves as obtained from the observations of Thorpe and Rodger
as given in Figs. 41 to 46. Confining our attention first of all
to the aliphatic hydrocarbons in Fig. 41 we see that near their
boiling-points, indicated by small circles in the figure, the fluidity