J. Dellacherie

Solubility of normal paraffin hydrocarbons (C20 to C24) and some of their binary mixtures (C22+C24) and (C23+C24) in ethylbenzene

Abstract We have measured the solubilities in ethylbenzene of all normal paraffins from eicosane (C20H42) to tetracosane (C24H50) and of 17 binary mixtures of {docosane (C22H46) + tetracosane} and of 11 binary mixtures of {tricosane (C23H48) + tetracosane}. The solubilities of the pure substances show the now well known even-odd alternation effect, the basis of which is the alternation of the properties of the low-temperature stable solids. The addition of a small amount of one n-paraffin to another significantly increases the solubility of the latter in ethylbenzene. The binary mixtures show pronounced non-ideality. They are more soluble in ethylbenzene than the corresponding ideal mixtures.

On the ideality of liquid mixtures of long-chain n-alkanes

Abstract Calorimetric measurements show that the heats of mixing two n-alkanes (of similar chainlength) in the liquid phase, are very small, and may often be neglected. Also, calculation of the entropy of n-alkane binary mixtures in the liquid and in the high temperature solid α-RII Rotator phase, by integration of experimentally obtained enthalpies, show that the excess entropies are negligible for all practical purposes. n-Alkane liquid mixtures between neighbouring homologs may therefore be considered as ideal solutions.

Dissolution of some normal alkanes in ethylbenzene: deduction of the enthalpy of mixing two n-alkanes in the solid state

Abstract Drop calorimetry has been used to measure the heat changes occurring upon the dissolution of some single n -alkanes (octadecane to tetracosane) or their binary mixtures (C 22 H 46 C 24 H 50 and C 23 H 48 C 24 H 50 ), in ethylbenzene, at 311.45 K. The enthalpy changes measured show the even-odd alternation effect known for n -alkanes. The binary mixtures show pronounced non-ideality. Their enthalpies of formation at 293.15 K were deduced from the measurement of their heats of dissolution in ethylbenzene and found to depend on the crystal type. It is shown that these mixtures may consist of several phases of solid solutions.

Excess thermodynamic properties of some binary solutions of ethylbenzene + n-alkanes

Abstract Some thermodynamic properties (excess enthalpies, entropies and Gibbs energies of mixing) have been determined for binary solutions of ethylbenzene + n -alkanes (eicosane, C 20 H 42 ; heneicosane, C 21 H 44 ; docosane, C 22 H 46 ; tricosane, C 23 H 48 ; and tetracosane, C 24 H 50 ), at crystallization temperatures in the (260–305) K range. The calculated properties vary with the chain lengths of the n -alkanes, and show the alternation effect occurring in the general behaviour of n -alkanes. Simple analytical expressions have been established to describe the excess properties.

Calorimetric measurement of molar excess enthalpies of dilute solutions of ethylbenzene + higher n-alkanes

Abstract Flow calorimetry has been used to measure the excess enthalpies (heats of mixing) of dilute solutions of higher n -alkanes (hexadecane to pentacosane) in ethylbenzene. The results show that at constant temperature and composition, h E increases with the number of carbon atoms in the n -alkane molecule. Also, for each alkane, h E decreases with increasing temperature, at constant composition. A simple analytical expression is used to represent the variation of h E with carbon number n , composition x , and temperature T in the domain (16 ≤ n ≤ 25; x ≤ 0.15; 298.15 ≤ T ≤ 330.00).

Mesure de la conductivite electrique totale du protoxyde de cobalt en fonction de sa composition definie par des electrodes d'alliage cobalt-platine, entre 1000 et 1400 K

Abstract The total electrical conductivity of cobaltous oxide has been measured from 1000 to 1400 K as a function of its composition, especially in the range of low oxygen pressures up to the limit of equilibrium with cobalt. These measurements have been carried out with monocrystalline samples of oxide placed between cobalt-platinum alloy electrodes; oxide composition is fixed by the activity of cobalt in the alloy which is also the activity of cobalt in oxide. Results are given by isotherm curves of the logarithm of conductivity versus the logarithm of oxygen pressure. The slope of these isotherms shows a regular variation between 1 4 and less than 1 6 ; this fact can only be explained by the successive effects of the formation of vacancies V″Co, V′Co and of intrinsic conductivity by electrons and free holes.