Jacobus G. Blok

The vapour pressure of benzoic acid

Abstract Vapour pressures of benzoic acid were measured in the temperature range 316 to 391 K with a capacitance diaphragm manometer. The results were fitted to a three-parameter equation: R 1n(p/p ° ) = −δG ° (θ)/θ+ δH(θ)(1/θ−1/T)+δC ° p (θ){θ/T−1 +1n(T/θ)} For the mean temperature θ = 353.15 K the thermodynamic-function changes are evaluated as: ΔGo(353.15 K) = −(10151±5) J · mol−1, ΔHo(353.15 K) = (89.45±0.05) kJ · mol−1, and ΔCpo(353.15 K) = −(48.4±5.0) J · K−1 · mol−1. A review of the literature data is given.

Liquid–vapour equilibria of the methyl esters of alkanoic acids: vapour pressures as a function of temperature and standard thermodynamic function changes

Abstract The vapour pressures as a function of temperature of the methyl esters of alkanoic acids from butanoic to eicosanoic acid, have been measured using two different techniques: the static diaphragm and spinning rotor manometry and the combined torsion mass-loss effusion. Combined with data available from literature, the new data have been processed using the thermodynamic regression equation proposed by Clarke and Glew. The results of this research are reliable vapour pressures and the thermodynamic properties of vaporisation.

Molar heat capacities and vapour pressures of solid and liquid benzophenone

Abstract Vapour pressures and heat capacities were measured for benzophenone. The triple-point temperature T tp was found to be (321.03±0.05) K, the vapour pressure at T tp being 1.33 Pa. The enthalpy of fusion is (18194±50) J·mol −1 . The enthalpy of sublimation is ΔH sub (321.03 K) = (94.7 ± 1) kJ·mol −1 . Coefficients of a vapour-pressure equation are given for the liquid and the solid phase.

Binary alkaline earth oxide mixtures: Estimation of the excess thermodynamic properties and calculation of the phase diagrams

Abstract A survey of available experimental excess thermodynamic properties for the binary alkaline earth oxide mixtures is given. The known excess thermodynamic properties of the oxide mixtures are evaluated and missing values are estimated by analogy with the binary common-ion alkali halide mixtures. The phase diagrams of the oxide mixtures corresponding to the evaluated / estimated excess properties are calculated and compared with the available experimental phase diagrams.

Thermodynamic properties of the normal alkanoic acids III. Enthalpies of vaporization and vapour pressures of 13 normal alkanoic acids

Abstract Torsion effusion and mass-loss effusion were used simultaneously to measure the vapour pressures of the normal alkanoic acids as a function of temperature. Overall mean values for both techniques are: nonanoic acid, ΔH o (303.98 K) = 85.3 kJ · mol −1 ; decanoic acid, ΔH o (313.77 K) = 88.6 kJ · mol −1 ; undecanoic acid, ΔH o (322.79 K) = 90.7 kJ · mol −1 ; dodecanoic acid, ΔH o (331.81 K) = 95.7 5 kJ · mol −1 ; tridecanoic acid, ΔH o (340.49 K) = 100.4 5 kJ · mol −1 ; tetradecanoic acid, ΔH o (348.59 K) = 104.1 kJ · mol −1 ; pentadecanoic acid, ΔH o (357.07 K) = 108.4 5 kJ · mol −1 ; hexadecanoic acid, ΔH o (364.14 K) = 110.2 5 kJ · mol −1 ; heptadecanoic acid, ΔH o (371.96 K) = 112.7 kJ · mol −1 ; octadecanoic acid, ΔH o (379.01 K) = 118.9 5 kJ · mol −1 ; nonadecanoic acid, ΔH o (386.13 K) = 121.8 kJ · mol −1 ; eicosanoic acid, ΔH o (392.53 K) = 125.5 kJ · mol −1 . The temperatures given are mid-range values at which the saturation vapour pressure is 0.4 Pa. The range of error in the enthalpies of vaporization is ±2 kJ · mol −1 . The literature vapour pressures for the alkanoic acids from hexanoic acid up to octadecanoic acid are reviewed. A vapour-pressure equation is presented which describes the liquid/vapour line from the triple-point to the normal boiling temperature. Using calorimetric data we determined the coefficients of an equation for estimating the vapour pressure of the solid phase.

Vapor pressures and lattice energies of oxalic acid, mesotartaric acid, phloroglucinol, myoinositol, and their hydrates

In the present investigation, we report the enthalpy of dehydration and the enthalpy of sublimation of a number of organic hydrates and their anhydrous counterparts. These values are used to test the transferability of a set of atom–atom potential parameters, originally derived for carboxylic acids. The calculations showed that the parameter set was transferable to a fairly good degree.

On the estimation of thermodynamic excess properties of binary solid solutions

An empirical estimation method for the heat of formation of solid solutions of binary mixtures of non-metallic chemically coherent substances from the lattice enthalpies of the pure substances is described. The method was tested on binary mixtures of the following groups of chemically coherent substances: alkali halides, alkaline earth oxides, p-dihalobenzenes and the cryogenic noble gases. Irrespective of the type of substance (ionic, molecular, atomic), the heat of formation of the solid solution as a function of composition could be estimated in good agreement with the experimental heat of formation data. An empirical estimation method for the characteristic temperature, the ratio of excess enthalpy and excess entropy, of binary solid solutions is described.

Binary common-ion alkali halide mixtures; a uniform description of the liquid and solid state

Abstract Empirical relations for the thermodynamic excess behaviour of binary common-ion alkali halide mixtures were derived. For the liquid state this gave rise to G E(1) ( x , T g ) = 0.68 H E(1) ( x , T g ) and S E(1) ( x , T g )=0.32 H E(1) ( x , T g )/ T g , and for the solid state G E(1) ( x , T )= A (1− T / (2565 K)) x (1− x )(1+ B (1−2 x )), in which the A parameter can be calculated from relative differences in unit cell volumes of the pure solid components A calc (kJ mol −1 ) = 11.53(Δ V / V s )+ 89.40(Δ V / V s ) 2 and the B parameter which is a measure for the asymmetry can be calculated from the A parameter using B = 1.04 × 10 −2 ( A calc /kJ mol −1 ). The phase diagrams were calculated and compared with experimental phase diagram data for twenty binary common-ion alkali halide systems that show complete sub-solidus miscibility.

SCANNING FORCE MICROSCOPY OF CHOLESTEROL MULTILAYERS PREPARED WITH THE SPIN-COATING TECHNIQUE

Abstract Multilayers of amphiphilic molecules are often prepared by the repeated transfer of a substrate through a Langmuir monolayer at the air/water interface. The Langmuir-Blodgett technique is not a suitable method for the construction of multilayers of cholesterol. In this study, the application of the spin-coating technique to the preparation of cholesterol multilayers was investigated. Scanning force microscopy was used to examine the morphology and thickness of cholestrrol films as a function of the frequency with which the substrate was spun, the concentration of the solution used to spin-coat the substrate, and the type of solvent. It was found that the amount of cholesterol that was deposited on the substrate was proportional to the concentration of the solution and to the inverse of the square root of the spinning frequency. Experiments performed with different solvents showed that, in cholesterol films were deposited on the substrate if the vapour pressure of the solvent was higher than 10 kPa at 298 K. Our results suggest that well-ordered cholesterol multilayers with adjustable thicknesses can be prepared with the spin-coating technique.

Vapour pressures of crystalline and liquid 1,4-dibromo- and 1,4-dichlorobenzene; lattice energies of 1,4-dihalobenzenes

Vapour pressure data as a function of temperature are presented for 1,4-dichlorobenzene and 1,4-dibromobenzene in the crystalline and liquid states. In addition, lattice energies of the two compounds are given together with these data for three other 1,4-dihalobenzenes, namely 1-bromo-4-chlorobenzene, 1-bromo-4-iodobenzene and 1-chloro-4-iodobenzene.