Eleuterio Luis Arancibia

Regression against temperature of gas chromatographic retention data

Abstract Specific retention volumes were measured in the range 25–75°C for benzene + squalane, benzene + triethylene glycol and n -hexane + squalane and in the range 15–55°C for benzene + tetraethylene glycol dimethyl ether, each in steps of 5°C. Values for the solution thermodynamic properties and their errors were obtained by fitting the experimental data to equations with two or more constant by using the method of Clarke and Glew. The best thermodynamic results were obtained by means of the three-constant equation; adding a fourth constant did not improve the adjustment. However, when the objective is interpolation, the results obtained with the classical, two-constant equation, are of adequate accuracy.

Thermodynamic study of the behaviour of two molten organic salts as stationary phases in gas chromatography

Abstract The gas chromatographic retention behaviour of hydrocarbons of different types and of a group of halogenated compounds was measured at four temperatures from 20 to 30°C in columns containing ethylammonium nitrate (EAN) or n-propylammonium nitrate (PAN) as stationary phases. Thermodynamic functions of solution calculated from these data are compared to those in non-ionic organic solvents and in water. The solvent behaviour of both molten salts fits well with those of other solvents of high cohensive energy. Alkanes and olefins are retained by mixed processes of solution and adsorption at the gas-liquid interface.

Gas chromatographic study of solution and adsorption of hydrocarbons on glycols : I. Diethylene glycol and triethylene glycol

Abstract Interfacial adsorption is shown to influence the gas chromatographic retention behaviour of hydrocarbons when using glycols as stationary phases. This interfacial effect can be neglected only for lower aromatic hydrocarbons, as demonstrated by the determination of partition and interfacial adsorption coefficients. Activity coefficient at infinite dilution were calculated; they compare favourably with those determined statically when using the method proposed by Martire et al. for the evaluation of exposed areas, whereas the use of experimental values given by Serpinet et al. led to erratic results. Solution and adsorption thermodynamic characteristics of the systems studied are briefly discussed.

Molar and partial molar excess volumes of di-n-butylamine with chloroalkanes at 25°C

Molar excess volumes and partial molar excess volumes are reported for binary mixtures of dibutylamine+dichloromethane, trichloromethane and tetrachloromethane at 25°C, over the whole concentration range. A comparative study is made between the primary and secondary amines and their mixtures with chloroalkanes. The applicability of the so-called ERAS model for predicting thermodynamic excess properties is tested here for excess molar volumes; the calculated values agree quite well with experimental data.

Thermodynamics of hydrocarbon solutions using g.l.c. n-Hexane, n-heptane, benzene, and toluene as solutes each at infinite dilution in n-hexadecane, in n-octadecane, and in n-eicosane

Abstract Infinite-dilution activity coefficients were measured by g.l.c. over a range of 50 K for n-hexane, n-heptane, benzene, and toluene in n-hexadecane, n-octadecane, and n-eicosane; measurements for cyclohexane and tetrachloromethane in n-hexadecane are also discussed. The experimental results were fitted to an adaptation of the equation of Clarke and Glew, thus calculating partial molar excess enthalpies and heat capacities. The results are compared with those obtained by extrapolation from static results at finite mole fractions.

Solution and adsorption thermodynamics in propylene glycol by gas chromatography : A comparative study with other polyhydroxylated solvents

Abstract The retention volumes of eighteen hydrocarbons representative of different families and of acetone, diisopropyl ether and three chloromethanes were measured at four temperatures within the range 12–22°C on columns containing five different percentages of propylene glycol (PG) as the stationary phase. The relative magnitudes of the adsorption on PG, on formamide and on four glycols are compared and discussed in terms of the thermodynamic properties of the bulk mixtures with hydrocarbons, From this comparison, PG is found to possess the weakest adsorption effects, and some of the solutes studied exhibit no adsorption within experimental error. The thermodynamic properties of solution in PG are calculated and compared to those in formamide and in the glycols. Recent extensions of the regular solutions model are inefficient for calculating infinite dilution activity coefficients, but yield a very acceptable correlation between heats of solution and solute solubility parameters.

Gas chromatographic study of solution and adsorption of hydrocarbons on glycols : II. Ethylene glycol☆

Abstract Adsorption at the gas-liquid interface is demonstrated in hydrocarbon-ethylene glycol systems. Thermodynamic properties of solution and adsorption at the gas-liquid interface of these systems were determined. The retention behaviour of olefins in ethylene glycol was studied. Values of retention parameters obtained from experimental data are compared with values in the literature; possible causes of discrepancies are discussed. The contribution of so-called Kelvin retention to the overall retention process was calculated and its significance for different systems is discussed.

Thermodynamic properties at infinite dilution of several solutes in ethers by gas-liquid chromatography

SummaryThe thermodynamic properties of different solutes at infinite dilution have been determined at 323.15 K. Deviations from ideality are discussed in terms of different contributions. The activity coefficients are compared with the calculated values by the one group contribution method.

Thermophysical Properties of the Ternary System 2-Methoxyethanol + Acetonitrile + 1,2-Dichloroethane, and the Binary Systems at 25°C

Excess molar volumes, change of refractive indexes, and deviation of dynamic viscosity of the 2-methoxyethanol + acetonitrile, 2-methoxyethanol + 1,2-dichloroethane, and acetonitrile + 1,2-dichloroethane binary systems and the excess molar volumes of 2-methoxyethanol + acetonitrile + 1,2-dichloroethane ternary system have been determined at 25°C and at atmospheric pressure, by measuring densities, refractive indexes, and viscosities over the entire range of composition. These derived data of binary and ternary mixtures were fitted to Redlich–Kister and Cibulka equations, respectively. An estimation of excess volumes is also evaluated using a modified Heller equation, which depends on the refractive indexes of the mixture. A comparison of the predictions by different methods with the experimental values of the physical properties has been made.

Isothermal vapor–liquid equilibria for the 1,1,1-trichloroethane+tetrahydrofuran+propan-2-ol system at 298.15 K

Abstract Isothermal vapor–liquid equilibria (VLE) for mixtures containing 1,1,1-trichloroethane+tetrahydrofuran+propan-2-ol have been measured using a modified version of a Boublik–Benson still at 298.15 K. A test of thermodynamic consistency, like McDermott–Ellis method was applied to the activity coefficients. Excess molar Gibbs free energies were calculated over the entire range composition. Different expressions existing in the literature were used to predict the activity coefficients.