Viscosity measurements have been made on nine pure hydrocarbon liquids at six temperatures ranging from 15.56° to 135°C and at pressures as high as 4000 bars. The samples included rigid bicyclic compounds of relatively high symmetry and three n-alkanes, n-C12, n-C15, and n-C18. These data were analyzed using the Eyring significant-structure theory, the Cohen—Turnbull free-volume model, and the empirical Doolittle equations. All of these equations produced essentially identical fits to the data at atmospheric pressure. The hypothesis that the constants v0 and vs in these equations represent the specific volume of a ``solid'' or condensed phase was tested by comparing best-fit values of these constants with experimental values for the solid-phase specific volume. The Cohen—Turnbull and Doolittle equations were modified for use at elevated pressures with the result that the values of v0 necessary to satisfy the equations at high pressures were shown to be analogous to the specific volumes of a glassy state at high pressures. Further, the change in v0 as a function of pressure was compared with the change in the experimental values of the solid-phase volume at the melting point as a function of pressure and a definite correlation between the two was established.

First order phase transitions were investigated for n-nonane, n-dodecane, n-tridecane, n-pentadecane, n-octadecane, and n-tetracosane, at pressures up to 10 kilobars and temperatures up to 135°C. By a modification of standard piezometric techniques, phase transition pressures, as well as the associated isothermal isobaric volume changes were determined at approximately 25°C intervals. Correlations established between the melting temperatures and the specific volume changes associated with phase transitions and the n-paraffin chain lengths show a strong dependence upon whether the n-paraffin is of odd or even species. This dependence becomes more pronounced at higher pressures. The specific volume, enthalpy, and entropy changes showed no dependence upon chain length at the same melting temperature.

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no higher than that of the known triplet state of benzene at 3.6 e.v.27'28 (28) Benzene vapor excited with X 2537 Á. (~4.8 e.v.) does not have enough energy to decompose to gaseous product. Cf. J. E.