Values of the limiting specific volume v0 calculated by a trial-and-error procedure from n-alkane viscosity data using the author's free-space viscosity equation, lnη=B(v0/vf)+lnA,agree substantially with previously published values obtained by extrapolation of density data. Values of v0 for mercury, sodium, benzene, carbon tetrachloride, dichlorodifluoromethane, and water were calculated by the same trial-and-error procedure. In all cases the free-space equation gave a much better fit than the corresponding Andrade temperature equation, lnη=B/T+lnA.

General equations for the temperature dependence of the parameters of the Hudleston equation are given which were deduced from a study of n-alkane compression data. Empirical expressions for the molecular-weight dependence of the constants of these equations are likewise given which are applicable only to n-alkanes. By use of these relations in the Hudleston equation the compressions of the family of liquid n-alkanes over ranges of T, P, and m were calculated on an IBM-650 computer. The over-all standard percentage error (SPE) of the computer calcufations for n-alkanes of 7 to 20 carbons up to temperatures not exceeding their normal boiling points was 0.10%. The over-all SPE for n-alkanes of 7 to 40 carbons up to temperatures substantially above their normal boiling points (but not exceeding 300°C.) was 0.21 %.Since the Hudleston ( 1 5 ) equation has been shown (8, 1 4 ) to represent pressure-volume data on liquids at constant temperature with high accuracy, it seemed desirable to investigate the temperature-dependent parameters of this equation so that it could be used as an equation of state for the purpose of making certain liquid-state thermodynamic calculations.To permit the calculation of compressions for all members of the n-alkane family, empirical equations for the molecular-weight dependence of all parameters involved were determined. These are applicable to the n-alkanes only. With all variables defined as functions of temperature and molecular weight, a trial-and-error solution of the Hudleston equation was programed for the IBM-650 computer, and a set of tables was listed giving the specific volumes of all the n-alkanes studied at their temperatures of measurement but at even pressures.The purpose of carrying out this empirical study was twofold: to determine the nature of the variation, particularly that of the temperature dependence, as a step toward a better understanding of the Iiquid state and to provide a body of compression data at even pressures for use in subsequent calculations involving the behavior of liquids.The apparatus and method used by Simon and Cornish to measure the volumes of liquids under pressure have been described ( 1 0) , and their data on eight n-alkanes of 7 to 40 carbons has been evaluated (8). It has been shown that the data for n-heptane and n-eicosane are very well represented by the Hudleston ( 1 5 ) equation. This paper considers all the Simon and Cornish data and the n-alkane data of other investigators for the purpose of establishing the temperature and molecularweight dependence of the parameters of the Hudleston equation. Dortha B. Doolittle is at the West Virginia Institute of Technology, Montgomery, West Virginia.

New measurements of the volumes of liquid n‐alkanes of 7, 9, 11, 13, 17, 20, 30, and 40 carbon atoms over a range of temperatures from 20° to 300°C. and pressures from 0 to 4,000 kg./sq. cm. have been made. These volume measurements are here reduced to compressions (vol)/(vol°T), and the accuracy of the measurements has been determined. Analysis of the data for n‐heptane and n‐eicosane shows that the order of accuracy of the compressions of each of these compounds appears to be approximately 3 parts in 10,000. Evaluation of random multiple measurements on the remaining six compounds indicates that their over‐all accuracy is likewise of this same order.