ACKNOWLEDGEMENTS

I thank Dean Henry Eyring for his suggestions, encouragement and example during the course of this research. I also thank […]exius I. Ree, Austin L. Wahrhaftig and Gilford A. Chappell for helpful discussions.

I acknowledge the financial assistance of the Department of Chemistry for teaching fellowships during the years 1960 to […], the National Science Foundation for a research fellowship during the summer of 1961, and the Office of Ordnance Research, United States Army for support during the years 1962 to 1964.

I gratefully acknowledge the assistance of the Computer […] personnel in making the calculations of this work possible.

I extend appreciation to Miss Sandra Hardy for typing this thesis.

ABSTRACT

Eyring's liquid theory has proven to be eminently more successful than existing theories in predicting properties of fluids. Objections to the parameters n and a in the positional degeneracy term of the partition function, however, have prevented a general acceptance of the theory. The number of nearest neighbors, n, has been reported in some cases to be larger than that of closest packing, 12, and a has been given seemingly arbitrary values to reproduce melting point properties. Also, the techniques used to determine these and other parameters of the partition function have been questioned. A mathematical examination of the various techniques employing two phase equilibrium data to determine the parameters n, a, θ, E_s and V_s has led to the conclusion that the significant structures partition function apparently does not describe the liquid-vapor equilibrium situation accurately enough to allow this equilibrium condition to be used in a mathematical parameter-determining technique without modification. As a result, the benzene and modified benzene techniques are based on an invalid restriction. A new technique is proposed which does not involve approximations or assumptions and avoids the above difficulty.

In order to remove the objections to the parameters a and n, a […]m of the basic solid-like partition function has been made to include the possibility of hindered intermolecular rotation. The hindered rotation partition function has been proposed having the form

f_{hindered rotation} = 1 + e^{−B₀RT(V − V_s0)/V_s} (f_{free rotation} − 1)

where B₀ is the rotational energy barrier and V_s0 is the molar volume of the solid just before rotation sets in at the transition point (which may be below or coincide with the melting point); V is the volume of the system and V_s is the molar volume of the solid after the transition point. Including the above partition function has allowed the more reasonable choice for n = 10.7 (the observed value for argon) and a universal value for a = .0052 (the calculated value for argon) to be used for the otherwise argon-like molecules CH₄, CCl₄, CH₃Cl, N₂ and Cl₂. Also the calculated critical point properties agree more closely with the observed values when hindered intermolecular rotation is considered than when the rotational degrees of freedom of the solid-like structure are taken to be completely free or as simple harmonic oscillations.