A.G. Williamson

Thermodynamics of ether solutions I. Enthalpies of mixing of ethers with carbon tetrachloride and with chloroform

Abstract Enthalpies of mixing at 25 °C and atmospheric pressure are reported for mixtures of diethyl ether, di- n -propyl ether, di- n -butyl ether, di- n -amyl ether, di- n -hexyl ether, di-isopropyl ether, di- tert -butyl ether, and di-isoamyl ether, with carbon tetrachloride and with chloroform. The enthalpies of mixing for all but one of the systems (di- n -butyl ether + carbon tetrachloride) are negative. The difference between the enthalpy of mixing of a given ether with carbon tetrachloride and that with chloroform is consistent with the existence of hydrogen bonding in the chloroform mixtures. The relations between the enthalpies of mixing of the branched chain ethers are not simple and appear to show both inductive and steric effects when the chain branching occurs near the oxygen.

Thermodynamics of ether solutions II. Volumes of mixing of ethers with carbon tetrachloride and with chloroform at 25 °C

A new apparatus for the measurement of volumes of mixing of liquids is described. The apparatus has been used to determine the volumes of mixing at 25 °C of mixtures of diethyl ether, di-n-propyl ether, di-n-butyl ether, di-n-amyl ether, di-n-hexyl ether, di-isopropyl ether, di-tert.-butyl ether, di-isoamyl ether with carbon tetracloride and with chloroform. The variation of volume of mixing with chain length is similar to that observed for enthalpies of mixing for the n-alkyl ethers. The effects of chain branching on volume of mixing are, however, not parallel to those on enthalpies of mixing.

Enthalpies and volumes of mixing of alkanes with carbon tetrachloride, chloroform, and methylene chloride at 25 °C

Enthalpies and volumes of mixing at 25 °C and atmospheric pressure are reported for mixtures of n -hexane and n -heptane with carbon tetrachloride, chloroform, and dichloromethane. All the enthalpies of mixing are positive and increase in the order CCl 4 , CHCl 3 , CH 2 Cl 2 . The volumes of mixing are all positive, varying from 0.04 cm 3 mol −1 for n -hexane + carbon tetrachloride to 0.8 cm 3 mol −1 for n -heptane and methylene chloride.

Vapour pressures and excess Gibbs energies of n-hexane and of n-heptane + carbon tetrachloride and + chloroform at 298.15 K

Abstract Liquid + vapour equilibrium measurements at 298.15 K are reported for n-hexane and for n-heptane + carbon tetrachloride and + chloroform. Excess Gibbs free energies have been derived from these results and are about +300 J mol−1 for alkane + carbon tetrachloride and about +100 J mol−1 for alkane + chloroform.

(Vapour + liquid) equilibria of (n-hexane + n-hexadecane), (n-hexane + n-octane), and (n-octane + n-hexadecane)

Abstract Vapour pressures using a static method have been measured for ( n -hexane + n -hexadecane), ( n -hexane + n -octane), and ( n -octane + n -hexadecane) at 298.15 K. The results have been fitted using a polynomial and agreement within experimental error was obtained. Excess molar Gibbs free energies calculated from the results and plotted against carbon number have been shown to agree well with the principle of congruence.

Accurate second virial coefficients of n-alkanes

Abstract Second virial coefficients are reported for n -pentane, n -hexane, and n -heptane in the temperature range 298.15 K to 373.15 K. The measurements are compared with those of other workers and the differences are examined. It is believed that the method used in this work leads to results which are a more accurate representation of second virial coefficients than has hitherto been obtained.

Excess volumes of ternary and quaternary mixtures of n-alkanes

Excess volumes have been measured at atmospheric pressure and 303.15 K for three- and four-component mixtures of n-alkanes. The results are in excellent agreement with values predicted from the data for n-hexane + n-hexadecane and the principle of congruence.

Excess molar enthalpies for (n-hexane + n-hexadecane) and for three- and four-component alkane mixtures simulating this binary mixture

Excess molar enthalpies HmE are reported at 0.1 MPa for {xC6H14 + (1−x)C16H34} at 298.15 and 303.15 K and for three- and four-component mixtures of n-alkanes, simulating the binary mixture, at 303.15 K. Isothermal dilution calorimetry was employed, using initial liquids which were either pure or binary mixtures with average carbon numbers of 6 and 16. The results for the multicomponent mixtures are compared with those for the binary mixtures via the principle of congruence which is found to be capable of correlating the results for all mixtures within 4 per cent of HmE(max.). Values of HmE(max.) for the multicomponent systems are slightly less than for the binary mixture and appear to decrease as the number of components increases.

Application of the principle of congruence to ternary alkane mixtures

Abstract Excess enthalpies and excess volumes at 298.15 K and atmospheric pressure have been measured for mixtures of n-hexane + (an equimolar mixture of n-tridecane + n-nonadecane). The agreement of the results with the corresponding results for mixtures of n-hexane + n-hexadecane is interpreted as confirmation of the applicability of the principle of congruence to multicomponent mixtures.

(Vapour + liquid) equilibria of (n-hexane + n-octane + n-hexadecane)

Abstract Vapour pressures and derived excess molar Gibbs energies are presented for (n-hexane + n-octane + n-hexadecane). The results are compared with those for independently measured binary mixtures as a test of the extension of the principle of congruence to the excess molar Gibbs energies of ternary mixtures. The results are also examined for internal consistency with the principle of congruence using the expectation of unity activity coefficient of one component in mixtures in which the average chain length of the ternary mixture is the same as that of the component whose activity coefficient is being considered.