Compressions of liquids. III. Temperature and molecular weight dependence of the Hudleston parameters for the n‐alkanes

Abstract

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.

A VSE equation of state for liquids. VI. Polymethylene 450–650 K

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PIG-B, a membrane protein of the endoplasmic reticulum with a large lumenal domain, is involved in transferring the third mannose of the GPI anchor.

“…The hydrophobicity profile is drawn using the algorithm of Kyte andDoolittle (1982) with a window setting of 11. The predicted amino acid sequence of the longest open reading frame is shown in single-letter codes below the nucleotide sequence.…”