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The specific retention volumes of 21 hydrocarbon solutes are measured on eight liquid phases at 80", loo", and 120°C. The infinite dilution activity 7oefficients and heats of solution are presented and compared with literature data.The basic physical process responsible for retention of a solute in gas-liquid partition chromatography is the partition of a solute or solutes between the gas and liquid phases. Because of this fact, much of the thermodynamic information attainable from a normal (static) solubility or vapor-pressure measurement is also obtainable from gas chromatographic retention volume measurements. In particular, numerous authors (7-4, 6, 8 , 77, 74-79, 25, 26, 28, 3 7 , 38, 3 9 ) have measured infinite dilution activity coefficients and/or other thermodynamic data such as heat of solution, entropy of solution, and partial molar excess enthalpies and entropies.Hydrocarbon systems have been studied extensively by this method. The activity coefficients of C4-Ca hydrocarbon solutes in n-hexadecane, n-heptadecane, and n-octadecane have been measured at lower temperatures (5, 73, 33, 4 7 ) . The normal hydrocarbons in the range c2O-c36 at higher temperatures ( >6O0C) have been studied by several investigators ( 2 0 , 32, 42, 4 5 ) ; however, the studies have been limited in scope, and there is little overlap of the data sets. Hicks and Young ( 2 0 ) studied n-butane, n-pentane, and n-hexane on n-tetracosane and n-octacosane; however, each measurement was at a separate temperature so that little correlation of this data is possible because of the temperature dependence of the activity coefficients in low-molecular-weight solvents at low temperatures. For higher molecular-weight systems at higher temperatures, the activity coefficient is generally independent of temperature, because of low values for the partial molar excess enthalpy of these systems. However, at lower temperatures the activity coefficients generally decrease with increasing temperatures; therefore, it is not advisable to compare data sets at different temperatures for low-molecular-weight systems.Martire and Pollara ( 3 2 ) , Young ( 4 5 ) , and Tewari et al. ( 4 2 ) all reported activity coefficient data for one or more solvents in the range 8O-12O0C, and this literature data will be compared with the results of this report in the Discussion section.Pease and Thorburn ( 3 7 ) have published V, data for 27 alkane solutes on n-octacosane, n-dotriacontane, and n-hexatriacontane at 8O.Oo, 100.0", and 120.0"C. This set of Vg data was used as a reference point for our Vg values, and the comparison will be given in the Discussion section.In many cases, the activity coefficients and heats of solution have been compared with data obtained from static isotherm, vapor pressure, or solubility data. The general conclusions ( 7 2 , 40, 4 3 ) are that the accuracy of the limiting activity coefficients and heats of solution are ' To whom correspondence should be addressed compatible with static data, and that the chromatographic approach offers sev...

Some fundamental factors influencing retention indices in gas-liquid chromato raphy are studied by the mathematical technique offactor analysis. Eight abstract eigenvectors are required to span the factor space and to reproduce the data matrix within experimental error. A scaling-test vector termed the uniqueness test is used to compare compounds in the scheme. A procedure is presented for accurately predicting a solute retention index on any stationary phase in the system if the retention indices of that solute on eight carefully chosen stationary phases are known. The procedure can also be used to predict retention indices of any solute in the system on a given stationary phase if the retention indices of eight chosen solutes on that column are known. The usefulness of this procedure for predicting retention indices is illustrated for four solutes which were purposely left out of the analysis. Using the rotation part of the factor analysis, the following solute physical parameters tested successfully as factors of the space: molar polarization and dipole moment squared.A solvent property which tested successfully was the uniqueness of etherlike linkages.

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