Heat Of Mixing Data Research Articles

Limitations of modern expressions for the excess Gibbs energy

The rational design of separation processes, such as distillation, extraction, etc., requires quantitative information on the phase equilibria of binary and multicomponent systems primarily as a function of composition and temperature. At low or moderate pressure Gibbs energy models are usually used in combination with a truncated form of the virial equation. With regard to the further development of g E-expressions, this paper describes tests of different modern g E-models for their ability to describe the separation factor as a function of concentration and temperature. Ethanol-benzene, ethanol-triethylamine and acetone-chloroform were used as test systems. The system ethanol-water was examined in greater detail because reliable VLE data and heats of mixing data are available for this system over a large temperature range. These data were completed in our laboratory by accurate Px-measurements in the temperature range 90 – 150°C using a static still.

Light Scattering Study of Local Structures in Solutions. Mean Association Numbers and Concentration Fluctuations for Alcohol–Carbon Tetrachloride Systems

Abstract Light scattering spectra were observed for carbon tetrachloride solutions of methanol, ethanol, and 1-propanol. The Rayleigh intensities were reduced to concentration fluctuations. The observed concentration dependence of the concentration fluctuation was analyzed by using two distinct models: an ideal associated complex (IAC) model and a polymer chain (PC) model. In the IAC model, a group of hydrogen-bonded alcohol molecules is treated as a complex whose size is independent of the association number, l. In the PC model, on the other hand, the group of hydrogen-bonded molecules is treated as a linear polymer whose length is proportional to l. It was shown that the PC model can explain both the concentration fluctuation and the heat of mixing data, while the IAC model cannot be applied to the present systems. The mean association number obtained by the IAC model was discussed on the basis of the relation between the concentration fluctuation and the spatial correlation of microscopic density.

The activity coefficients of some polar solutes in benzene

Cryoscopy was used to determine the low concentration (< 1 molal) stoichiometric molal activity coefficients of: chlorobenzene, m-dichlorobenzene, o-dichlorobenzene, and nitromethane in benzene. The data were corrected to a fixed temperature (10 °C) by using pre-existing heat of mixing data. The activity coefficients all showed negative deviations from Henry's law ideality, and some of the factors that contribute to this non-ideality were discussed.

Prediction of ternary heat of mixing from binary vapor‐liquid equilibrium and heat of mixing data by using wilson equation

Prediction of ternary heat of mixing from binary vapor‐liquid equilibrium and heat of mixing data by using wilson equation

Excess gibbs free energies and heats of mixing for binary alcoholic liquid mixtures.

Phase equilibria were studied in the systems methanol-methyl ethyl ketone, ethanol-methyl ethyl ketone, methyl ethyl ketone-2-propanol, methyl acetate-1-propanol, and methyl acetate-2-propanol under isothermal conditions. Heat of mixing data were obtained for these systems. The Wilson and NRTL equations were able to represent simultaneously these two kinds of thermodynamic quantities under the assumption that their parameters were temperature-dependent.

Excess enthalpies and excess volumes of binary mixtures containing tetrahydrofuran

Heat of mixing data at 318.15 K are reported for the binary systems made up of tetrahydrofuran (THF) with pyridine and with thiazole. The volumes of mixing at 298.15 K and atmospheric pressure have also been measured for the following binary mixtures: THF+pyridine, THF+thiazole THF + benzene, THF + cyclohexane, THF + hexafluorobenzene.

Experimental heats of mixing for gaseous nitrogen and methane

AbstractThe excess enthalpy of binary gas phase mixtures has been measured by direct experiment, using a continuous flow, isothermal colorimeter. Heat of mixing data are presented for the methane‐nitrogen system for compositions of 25 to 80 mole % methane in nitrogen, at temperatures of 40°, 0°, −20°, −40°, −60°, and −78°C. and pressures from 250 to 1,50 lb./sq. in. abs. These data are in agreement with the literature to within the experimental uncertainty of this work, 4%.The experimental results agree well with values predicted using the Benedict‐Webb‐Rubin and the Redlich‐Kwong equations of state. The virial equation of state truncated after the third coefficient fits the low density data only. The liquid theories of Scott predict the enthalpies of the mixtures in a qualitative way.

Some preliminary investigations of the phenolformaldehyde reaction

AbstractThe reaction between phenol and formaldehyde, takes place us a series of step‐wise reactions which are catalysed by both acids and bases and which proceed under neutral conditions at sufficiently high temperatures. Two types of reaction take place, namely the reaction of formaldehyde with phenol or a phenolic molecule, to form phenolic alcohols containing reacting methylol groups, and the subsequent condensation of these phenolic alcohols with phenol or a phenolic molecule to form larger molecules with elimination of water. Two studies of the initial portion of the reaction between phenol and formaldehyde in aqueous media are described, namely the Kinetics and the Thermochemistry.Kinetic studies show that a linear relationship exists between antilog (—pH) and the initial rate at which the formaldehyde reacts using HCl as catalyst between pH values of 1·3 and 3 at 100° and 80°. Catalysis by different acids at the same pH value gives rise to similar rates of reaction especially when pH and rate of reaction are measured at the same temperature. This points to catalysis by the hydrogen ion. The second order rate law is best obeyed by all the curves relating to formaldehyde reacted and time at various pH values, at 100° and 80° using HCl as catalyst. A decrease in temperature to 30° causes the rate law to approach first order. A theoretical enquiry shows that a decrease in order of reaction could be explained by the formation of dialcohols, which formation of dialcohols seems more probable at low temperature. In alkaline media, dialcohols also seem to be produced more readily, us indicated by the fact that a first order rate law is obeyed until about 45% of the formaldehyde has reacted.Thermochemical studies show that the heat evolved during the phenolformaldehyde reaction may also be regarded as derived from the reaction of formaldehyde with a phenolic molecule, and the subsequent elimination of water by condensation. The heats evolved per mole of formaldehyde reacted and water evolved are 4·1 and 16·9 kilocalories respectively. These values are confirmed by combining heats of combustion and heats of mixing data.

LIQUID–VAPOUR EQUILIBRIUM FOR THE SYSTEM ETHANOL–ACETONE

Vapour pressures and equilibrium liquid–vapour mole fractions have been determined for the solvent system ethanol–acetone at 32°, 40°, and 48 °C. in a modified form of the apparatus developed by Ferguson and Funnell. It is shown that the data are consistent with the Gibbs Duhem equation if it be assumed that deviations from ideality in the vapours may be computed from the principle of Corresponding States. It is also shown that the variation of the activities of the components in the liquid with temperature is in moderate agreement with the heat of mixing data for the system.