Isothermal Displacement Calorimeter Research Articles

Effect of Cadmium Chloride and Ammonium Chloride Salts on the Enthalpy of Mixing of Pyridine + Water at 303.15 K

In this work, the effect of two dissolved inorganic salts (cadmium chloride, CdCl2; ammonium chloride, NH4Cl) on the enthalpy of mixing (HE) of the pyridine + water binary system measured at 303.15 K using an isothermal displacement calorimeter with vapor space is investigated. Compared with the salt-free system, the addition (0.05 mass fraction) of the salts altered the magnitude of HE values to some extent depending on the mole fraction of x1. The importance of the solute–solvent and solvent–solvent interactions was demonstrated from the increasing exothermic HE values with increasing salt concentration (0.10 mass fraction). The experimental values of HE were fitted into the Redlich–Kister polynomial, and the adjustable parameters obtained by the least-squares method are reported.

Effect of Calcium chloride and Cadmium chloride on the enthalpy of mixing of 1,4 Dioxane + Water at 303.15 K

This paper presents the effect of two dissolved inorganic salts, CaCl2 and CdCl2 on the enthalpy of mixing of the binary 1,4 dioxane + water system has been investigated at 303.15 K in an isothermal displacement calorimeter with vapour space. A significantly increasing trend in the endothermic excess enthalpy values for the addition of calcium chloride and cadmium chloride were noticed. The experimental values of HE were fitted into the Redlich –Kister equation, and deviations from the ideal value and binary parameters were calculated. The importance of solute–solvent interactions was demonstrated from the excess enthalpy of mixing in the positive direction with an increase in the salt concentration.

Effect of Dissolved Cadmium Chloride and Ammonium Chloride Salts on the Enthalpy of Mixing of the Methanol + Benzene System at 303.15 K

The effect of two dissolved inorganic salts, cadmium chloride CdCl 2 and ammonium chloride NH 4Cl, on the excess enthalpy of mixing ( H E) of the binary system methanol + benzene measured at 303.15 K using an isothermal displacement calorimeter with vapor space is investigated in the present work. Compared to the salt-free system, a decreasing trend in the endothermicity of H E values is significant with the addition of CdCl 2 salt but the decrease in the H E values is insignificantly smaller with the addition of NH 4Cl salt. The experimental values of the enthalpy of mixing are fitted into a Redlich-Kister equation and the deviations in the values and the parameters are reported. The importance of the solute-solvent interactions and the solvent-solvent interactions are demonstrated from the increasing excess enthalpy of mixing values in the positive direction with the increase of salt concentration.

Effect of Dissolved Inorganic Salts on the Enthalpy of Mixing of the Ethanol + Pyridine System at 303.15 K

This paper presents the effect of five dissolved inorganic salts (sodium chloride, NaCl; calcium chloride, CaCl2; zinc chloride, ZnCl2; cadmium chloride, CdCl2; ammonium chloride, NH4Cl) on the enthalpy of mixing (HE) of the binary system ethanol + pyridine measured at 303.15 K using an isothermal displacement calorimeter with vapor space. Compared to the salt-free system, the addition of selected salts (0.05 mass fraction) significantly increased the HE values along the negative direction in the order of ZnCl2 > NaCl > CdCl2 ≈ CaCl2 > NH4Cl. With increasing salt concentration (0.10 mass fraction), the HE values decreased in the positive direction for the salt CdCl2 and increased in the negative direction for the salt CaCl2 which exemplifies the importance of solute−pyridine interaction. The experimental values of HE were fitted into the Redlich−Kister equation, and the deviations from the ideal value and binary parameters are reported.

Salt effect on the enthalpy of mixing of 2-propanol + acetic acid at 303.15 K

Salt effect on the enthalpy of mixing of 2-propanol + acetic acid at 303.15 K This paper presents the effect of two dissolved inorganic salts (zinc chloride, ZnCl2 and ammonium chloride, NH4Cl) on the enthalpy of mixing (H E) of 2-propanol + acetic acid binary system measured at 303.15 K using an isothermal displacement calorimeter with vapour space. A decreasing trend in the excess enthalpy of mixing values in the presence of ZnCl2 and NH4Cl indicate the endothermic behavior of this system. The Redlich-Kister equation has been used to fit the experimental H E data. The deviations from the ideal value and binary parameters were calculated and reported.

Determination and Correlation of Excess Enthalpies of Mixing of Ethyl Acetate/Benzene Mixtures Containing Dissolved Inorganic Salts at 303.15 K

This communication presents the effect of five dissolved inorganic salts (sodium chloride, NaCl; calcium chloride, CaCl2; zinc chloride, ZnCl2; cadmium chloride, CdCl2; ammonium chloride, NH4Cl) on the enthalpy of mixing (HE) of ethyl acetate/benzene binary system at 303.15 K; enthalpy measurements were performed using an isothermal displacement calorimeter with vapor space. The excess enthalpy of mixing of this system is significantly reduced in the presence of NH4Cl and NaCl; however, changes in the excess enthalpy of mixing were insignificant in the presence of CaCl2, ZnCl2, and CdCl2. The experimental values of HE were fitted into the Redlich–Kister equation, and deviations from the ideal value and binary parameters were calculated. The importance of solute–solvent interactions was demonstrated from the decrease in the excess enthalpy of mixing in the negative direction with an increase in the NaCl concentration.

Effect of Dissolved Salts on the Enthalpy of Mixing of the Methanol + Formic Acid System at 303.15 K

This paper presents the effect of four dissolved inorganic salts (sodium chloride, cadmium chloride, zinc chloride, and ammonium chloride) on the enthalpy of mixing of the binary system methanol + formic acid measured at 303.15 K using an isothermal displacement calorimeter with vapor space. A significantly increasing trend in excess enthalpy values for the salt cadmium chloride, an insignificant but small increase in the excess enthalpy for the salt zinc chloride, and a smaller but similar decrease in the excess enthalpy values with the addition of sodium chloride and ammonium chloride were noticed. The experimental values of the enthalpy of mixing were fitted into a modified Redlich−Kister equation, and the deviations and parameters are reported. Importance of the solute−formic acid interaction is demonstrated by the enhanced excess enthalpy of mixing (HE) values in the positive direction with increasing salt (ammonium chloride) concentration.

Salt Effect on the Enthalpy of Mixing of 1,4-Dioxane + Formic Acid at 303.15 K

This paper presents the effect of five dissolved salts (sodium chloride, calcium chloride, zinc chloride, cadmium chloride, and ammonium chloride) on the endothermic enthalpy of mixing of the binary system 1,4-dioxane + formic acid measured at 303.15 K using an isothermal displacement calorimeter with vapor space. The salt sodium chloride increases the excess enthalpy values to an extent. A significantly increasing trend in excess enthalpy values for the salt calcium chloride, a remarkably decreased excess enthalpy for the salt ammonium chloride, and a comparatively smaller decrease in the excess enthalpy with the addition of zinc chloride and cadmium chloride were noticed. The experimental values of the enthalpy of mixing were fitted into a modified Redlich−Kister equation, and the deviations and parameters are reported. While the excess enthalpies of mixing (HE) are more positive for the salts sodium chloride, cadmium chloride, and ammonium chloride, those for the salts calcium chloride and zinc chlorid...

Salt Effect on the Enthalpy of Mixing of 1,4-Dioxane + Acetic Acid at 303.15 K

The effect of five dissolved salts (sodium chloride, calcium chloride, zinc chloride, cadmium chloride, and ammonium chloride) on the enthalpy of mixing of the binary system 1,4-dioxane + acetic acid has been investigated at 303.15 K in an isothermal displacement calorimeter with vapor space. A decreasing trend in excess enthalpy for the salts NH4Cl and NaCl but an increasing trend for the salts CaCl2, ZnCl2, and CdCl2 with increasing salt concentration was observed. The Redlich−Kister equation has been used to fit the experimental enthalpy of mixing data, and the binary parameters have been estimated.

Enthalpies of solution of carbon dioxide in mixed solvents

The enthalpy of solution of carbon dioxide at effectively infinite dilution in various concentrations of sulfolane+water, N-methyldiethanolamine (MDEA)+sulfolane+water and MDEA+piperazine (PZ)+water have been determined using a modified isothermal displacement calorimeter.

Excess enthalpies of n-butanol + ethyl esters

Excess molar enthalpies of n-butanol +ethyl acetate, +ethyl propionate, +ethyl n-butyrate, +ethyl n-valerate, +ethyl n-caproate have been measured at 308.15 K with a Martin-type isothermal displacement calorimeter. The UNIQUAC model is successfully used to correlate the H l m of the five binary systems.

Excess enthalpies of seven binary liquid systems

A Martin-type isothermal displacement calorimeter was constructed for the determination of excess enthalpies of binary mixtures. Seven binary liquid systems of cyclohexane + benzene, + n-hexane, ethanol + benzene, n-butanol + methyl acetate, + ethyl acetate, + n-propyl acetate and + n-butyl acetate were investigated.

Thermodynamic properties of aqueous mixtures of hydrophilic compounds 2. Aminoethanol and its methyl derivatives

The vapour pressures of water + 2-aminoethanol, + N-methyl-2-aminoethanol, and + N,N-dimethyl-2-aminoethanol at 298.15 and 308.15 K were measured over the whole composition range by a static method. The excess enthalpies and densities of the same mixtures at 298.15 K were also measured with an isothermal displacement calorimeter and a pyknometer. The thermodynamic excess functions: G E, H E, TS E, and V E were calculated. Except for aminoethanol-rich region in (water + N,N-dimethyl-2-aminoethanol), where G E is slightly positive, the signs and relative magnitudes of molar excess functions were 0 > G E>TS E>H E, V E < 0. These are in accordance with general characteristics of (water + a highly hydrophilic compound). However, hydrophobicity is clearly seen for dilute aqueous solutions where the partial molar volume of aminoethanol exhibits a minimum and the partial molar enthalpy decreases rapidly to a limiting value at infinite dilution. This tendency increases with the introduction of methyl groups into 2-aminoethanol.

Excess enthalpies of (chloroform + cyclohexane), (propan-2-ol + toluene + cyclohexane), and (propan-2-ol + chloroform + cyclohexane) at 298.15 K

Excess enthalpies obtained with an isothermal displacement calorimeter for (chloroform + cyclohexane), (propan-2-ol + toluene + cyclohexane), and (propan-2-ol + chloroform + cyclohexane) at 298.15 K are presented. The results are correlated using two existing methods.

The isothermal displacement calorimeter: Design modifications for measuring exothermic enthalpies of mixing

The isothermal displacement calorimeter described previously has been modified by the inclusion of a thermoelectric cooling module to allow the study of both endothermic and exothermic mixing. Other modifications are also described. Excess enthalpies are reported for 1,4-dioxan+tetrachloro-methane, benzene+dichloromethane, tetrahydrofuran+water, and ethanol+water at 298.15 K and 1,4- dioxan+dichloromethane at 298.15 and 303.15 K. These mixtures have been suggested as possible reference mixtures for either checking the operation of, or calibrating, calorimeters to be used for making measurements on exothermic mixtures. The performances of our calorimeters have been evaluated on the basis of the results presented here and by comparison with previous results. Some advantages and disadvantages of the proposed reference mixtures are discussed. Photochemical effects from the tungsten thermostat lamp affect the results for mixtures of tetra-chloromethane with 1,4-dioxan.

An isothermal displacement calorimeter for the measurement of the enthalpy of solution of gases

The isothermal displacement calorimeter initially described by Stokes, Marsh and Tomlins has been modified to allow the measurement of the enthalpy of solution of gases. This paper reports the enthalpy of solution of argon and nitrogen in tetrachloromethane, cyclohexane, and benzene at 298.15 K and the enthalpy of solution of carbon dioxide, methane, ethane, ethene, and propane in the above three solvents at 298.15 and 318.15 K. Comparisons are made with other direct measurements and with results derived from the variation of gas solubility with temperature. The apparatus appears to have a higher precision than those described previously. For carbon dioxide and the hydrocarbon gases the precision is of the order of �0.2 kJ mol-1, while for argon and nitrogen the precision is of the order of �0.5 kJ mol-1.

Excess enthalpies of hexafluorobenzene + diethyl ether, + di-isopropyl ether, and + di- n-butyl ether at 283.15 and 298.15 K

The excess enthalpies of hexafluorobenzene + di-ethyl ether, + di- i-propyl ether, and + di- n-butyl ether have been measured at 283.15 and 298.15 K using an isothermal displacement calorimeter with some novel design features. The results indicate that the nature of the attached hydrocarbon chain may obscure the role of the ether oxygen atom in these mixtures.

An isothermal displacement calorimeter for positive excess enthalpies

An isothermal displacement calorimeter has been constructed on the basis of the successful design of the Armidale group. (1,2) The most important changes in the design are (a) a stainless-steel construction was used instead of a glass one, (b) the dead space has been elimiated by introducing the stirrer shaft from below, (c) the degassed liquids are injected without any contact with air, and (d) the energy is measured by using a pulsed heater circuit instead of the conventional time-switching method. Calibration was carried out using benzene + carbon tetrachloride and benzene + cyclohexane at 298.15 K. The standard deviation are 0.10 and 0.45 J mol −1 respectively. Our results are in good agreement with those obtained by other investigators.

Excess enthalpies and volumes for N,N-dimethylacetamide + n-alcohols at 298.15 K

Molar excess enthalpies and volumes for methanol +, ethanol +, 1-propanol +, 1-butanol +, heptane ( H E only) +, and cyclohexane ( V E only) + N,N-dimethylacetamide and isopropyl ether + heptane were measured at 298.15 K, by using an isothermal displacement calorimeter and a double-stem pyknometer. Molar excess energies at constant total volume were calculated from these results and were analyzed in terms of quasilattice theory.

Excess functions for cyclohexane + cycloheptane and cycloheptane + cyclo-octane

Excess enthalpies H E and excess volumes V E of cyclohexane + cycloheptane and cycloheptane + cyclo-octane have been determined at 288.15, 298.15, and 318.15 K by use of an isothermal displacement calorimeter and a dilution dilatometer, respectively. Vapour pressures of cyclohexane + cycloheptane at 298.15 K and of cycloheptane + cyclo-octane at 318.15 K were measured by a precise static technique. The excess Gibbs free energies G E at 288.15, 298.15, and 318.15 K were calculated from the vapour pressures and the temperature dependence of H E. Isothermal compressibilities for cyclohexane + cycloheptane were measured at 298.15 K by use of a dilution piezometer.