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The dependence of the several sources of solute retention in chromatography-bulk liquid partition, liquid interfacial adsorption, and solid support adsorption-on solvent volume and on surface areas is considered for a variety of practical situations. The relative magnitudes of the individual contributions may then be qualitatively predicted over a wide range of stationary phase loadings, for the situations of (a) constant sample size and (b) constant concentration of solute in the mobile phase. The individual contributions are finally summed to show qualitatively the various forms of variation of the net retention volume with liquid loading which may be met with in practice. The results are presented in graphical form. Certain features are found in these curves which are useful for diagnosis of interfacial adsorption effects in chromatography. The predicted curves are in formal agreement with published experimental plots, Means for the recognition of and correction for interfacial adsorption effects in experimental data are suggested, For chromatographic systems in which all three mechanisms occur, only bulk liquid partition coefficients can be determined unequivocally by chromatography alone.The range of application of chromatography to the measurement of physicochemical data is considerably broadened by these conclusions.

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The retention theory of gas chromatography is extended to finite concentrations of solute. The detailed treatment takes account of gas compressibility, gas imperfection and variation in velocity of the mobile gas phase due to flux of solute molecules across the interphase boundary. The compressibility-corrected retention volume V i of a chromatographic zone of given gas phase concentration c is shown to be related to the gradient (8q/8c)p of the partition isotherm by the equation, VG is the compressibility-corrected gas hold-up; Vl is the volume of solvent component in the stationary phase in gas-liquid chromatography ; P is a defined mean column pressure ; yo is the mole fraction of solute in the gas phase at the column outlet, corresponding to concentration c ; and a and j represent expressions which, for a gas phase showing only moderate deviation from the perfect gas law, are closely approximated by unity and the conventional James-Martin compressibility factor, respectively. A similar equation holds for gas-solid chromatography. The equation becomes inaccurate at high solute concentrations if gas imperfection is large ; estimates of the range of conditions in which the equation is valid are made. v-; = VG+ Vl(1 -air,)(aq/wp.Gas chromatography (GC) has been established as a rapid, simple and accurate means of determining thermodynamic properties at infinite dilution for binary, nonelectrolyte solutions and for gas-solid systems. In contrast, small effort has been expended in the application of these techniques to studies at finite concentration. Such an extension would provide a more convenient and rapid means of obtairaing extensive data on solute-solvent and adsorbent-adsorbate interactions than do more conventional methods.GC can be used to make measurements in the finite concentration range in several distinct, but related, ways, involving both frontal and elution modes of operation. The object of the present series of papers is, first, to develop the necessary theory and, secondly, to evaluate the methods experimentally. In this paper we develop a retention theory of gas chromatography generalized to finite concentrations of the volatile component. Although the treatment refers specifically to gas-liquid chromatography (GLC), gas-solid chromatography (GSC) is entirely analogous, and the result will be stated for both GLC and GSC.