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I. A numerical method was developed for smoothing thermodynamic data with a digital computer. As a feasibility study, data on specific volume and enthalpy from the skeleton tables of the Sixth International Conference on the Properties of Steam and from the tables of Keenan and Keyes were smoothed and interpolated. Orthogonal polynomials of temperature and pressure were used as the smoothing functions. In order to maintain thermodynamic onsistency between the smoothed values of the two thermodynamic properties, Lagrange multipliers were used in conjunction with least squares techniques to accomplish the curve fitting. Excellent agreement was obtained between tabulated and smoothed values of the above properties and their derivatives except near the critical region where data were sparse. The method is recommended for the smoothing of the above and other thermodynamic properties which may be subject to consistency restrictions.

II. Data on the Chapman-Cowling diffusion coefficients of liquid hydrocarbons were expressed analytically in terms of the physical properties of the liquid phase and the nature of the components. The weight fraction of the light component, temperature, and the molecular weight of the heavy component served satisfactorily as independent variables to describe the recent data of Sage for binary hydrocarbon systems. The results permit the calculation of the Chapman-Cowling diffusion coefficients in the liquid phase for saturated hydrocarbons from methane through n-decane.

III. The above data were used in the testing and formulation of correlations of diffusion coefficients of binary liquid mixtures. The correlation methods which were tested were the following: empirical, rate process theory, hole theory, and kinetic theory. The hole theory was inadequate for describing the available data on mutual diffusion; accurate empirical and rate-process expressions were developed for calculating Chapman-Cowling diffusion coefficients for binary mixtures of methane and ethane with heavier hydrocarbons through n-decane and a heavier "white oil;" although the expressions which were tested from kinetic theory did not predict correctly the dependence of the data on temperature and composition, they presented good approximations and appeared to be a promising area for future development.

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