Daniel Balesdent

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.

Variation in enthalpy of the systemn-tetracosane-n-hexacosane as functions of temperature and composition

Differential enthalpy analyses were performed on the binaryn-alkane systemn-C24H50-n-C26H54 with a Setaram DSC111 calorimeter of Tian Calvet type.The measurements provided enthalpy data from 260 to 260 K onn-tetracosane,n-hexacosane and 19 binary mixtures.An analytical expression, derived from the Einstein model, is proposed for every pure phase in its temperature domain, to represent the variation in the enthalpy with temperature.A general expression for the enthalpy as a function of temperature and composition is also given.

Diagramme de phases et proprietes thermodynamiques du systeme cadmium—plomb

Abstract A solid—liquid phase equilibrium diagram of cadmium—lead has been obtained by thermal analysis. The eutectic point is observed at TE = 520.9 ± 0.3 K for the mole fraction of lead xPb = 0.716 ± 0.004. The lack of solubility of lead in solid cadmium allows the calculation of the activity of cadmium along the liquidus curve for the mole fraction of lead xPb

Enthalpy variation of the nine solid phases of the binary molecular alloys (n-tricosane:n-pentacosane) vs. temperature

The enthalpy variations of pure n-tricosane (n-C23H48), pure n-pentacosane (n-C25H52) and sixteen binary mixtures were determined from 282 to 360 K. The differential enthalpy analyses were carried out on the pure components on the four terminal solid solutions, denoted βo(C23), β′o(C23), β′o(C25), βo(C25) and on the three intermediate phases, called β″1, β′1, β″2of the binary system (C23:C25) using a calorimeter of the Tian Calvet type. These variations can be represented by an analytical expression, which is derived from Einstein‘s model. The two Rotator phases β-RI and α-RII were also studied.

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).

Détermination expérimentale du diagramme de phase du système chlorure de cadmium-chlorure de potassium

Abstract A solid liquid phase equilibria diagram of Cd Cl 2 K Cl has been obtained by thermal analysis. X-ray diffraction confirms deposition of pure components and of two compounds (Cd Cl 2 · K Cl) and (Cd Cl 2 · 4 K Cl). The first is congruently melting; the second is incongruently melting. Two eutectic and one peritectic transforms are observed for the mole fractions of K Cl 0.344, 0.620, 0.685 at the temperatures 658.5 K, 663.4 K, 733 K.

Chemical potential of sulphur in (copper + sulphur) by thermogravimetry of copper sulphide in a gaseous mixture of H2 and H2S between 633 and 1033 K

The chemical potential of sulphur was measured in (copper + sulphur) by the thermogravimetric equilibrium of non-stoichiometric copper sulphide with a gaseous mixture of H2 and H2S. The mole ratio of H2S to H2 varying from 0.001 to 3 and the temperature between 633 and 1033 K, the formula of the sulphide departed from the stoichiometry Cu2S as far as Cu1.92S. Results show the stability regions of digenite, chalcocite, and these two phases. In the one-phase regions, for the weaker departures from stoichiometry, experimental values are well portrayed by the relation: ln ϱ = 2 ln δ + B, where ϱ is the ratio of the partial pressures of H2S to H2, δ is the departure (2−y) from the value 2 of y in CuyS; values of B are given against temperature. A structural meaning of this relation is proposed.