Measurements of HmE and VmE for (n-butane + sulphur hexafluoride) in the supercritical region at the pressure 6.00 MPa

A flow mixing calorimeter followed by a vibrating-tube densimeter has been used to measure excess molar enthalpies H_m^E and excess molar volumes V_m^E of {xC₄H₁₀+(1−x)SF₆}. Measurements over a range of mole fractions x have been made in the supercritical region at the pressure p=6.00 MPa and at seven temperatures in the range T=311.25 K to T=425.55 K. The H_m^E(x) measurements at T=351.35 K were found to exhibit an unusual double maximum. Measurements at all temperatures are compared with the Patel–Teja equation of state with the parameters determined by solving a cubic equation as recommended, and also with parameters determined by the method suggested by Valderamma and Cisternas who proposed equations which are a function of the critical compression factor. The overall fit to the H_m^E and V_m^E measurements obtained using Valderamma and Cisternas equations was found to be better than that obtained using the parameters according to the method suggested by Patel and Teja.     

Excess enthalpies and excess volumes of 1-nitropropane +, and 2-nitro-propane +, each of several non-polar liquids

Excess molar enthalpies H_m^E and excess molar volumes V_m^E have been measured for xC₃H₇NO₂ + (1 ? x)c-C₆H₁₂ at 298.15 and 318.15 K; +(1 ? x)CCl₄ at 298.15 and 318.15 K; +(1 ? x)C₆H₆ at 298.15 and 318.15 K; +(1 ? x)C₆H₁₄ (V_m^E only) at 298.15 K; +(1 ? x)p-C₆H₄(CH₃)₂ at 298.15 K; and for xCH₃CH(NO₂)CH₃ + (1 ? x)c-C₆H₁₂ at 298.15 and 318.15 K; +(1 ? x)CCl₄ at 298.15 and 318.15 K; +(1 ? x)C₆H₆ at 298.15 K; +(1 ? x)C₆H₁₄ at 298.15 K; +(1 ? x)(CH₃)₂CHCH(CH₃)₂ for H_m^E at 318.15 K and for V_m^E at 298.15 K; and +(1 ? x)C₁₆H₃₄ at 298.15 K. The H_m^E′s were determined with an isothermal dilution calorimeter and the V_m^E′s with a continuous-dilution dilatometer. Particular attention was paid to the region dilute in nitroalkane. In general H_m^E is large and positive for (a nitropropane + an alkane), less positive for (a nitropropane + tetrachloromethane), and small for (a nitropropane + benzene) and for (a nitropropane + 1,4-dimethylbenzene). The mixture with hexadecane shows phase separation. V_m^E is large and positive for (1-nitropropane + cyclohexane), less positive for (1-nitropropane + hexane), and S-shaped for (1-nitropropane + tetrachloromethane) with negative values in the 1-nitropropane-rich region. For (1-nitropropane + benzene) and for (1-nitropropane + 1,4-dimethylbenzene) V_m^E is negative. For mixtures with 2-nitropropane the results are similar except that for benzene V_m^E is S-shaped with positive values in the 2-nitropropane-rich region.     

Excess molar quantities of (a halogenated n-alkane + an n-alkane) A comparative study of mixtures containing either 1-chlorobutane or 1,4-dichlorobutane

Excess molar volumes V_m^E at 298.15 K were obtained, as a function of mole fraction x, for series I: {x1-C₄H₉Cl + (1 ? x)n-C_lH_{2l + 2}}, and II: {x1,4-C₄H₈Cl₂ + (1 ? x)n-C_lH_{2l + 2}}, for l = 7, 10, and 14. 10, and 14. The instrument used was a vibrating-tube densimeter. For the same mixtures at the same temperature, a Picker flow calorimeter was used to measure excess molar heat capacities C_{p, m}^E at constant pressure. V_m^E is positive for all mixtures in series I: at x = 0.5, V_m^E/(cm³ · mol^?1) is 0.277 for l = 7, 0.388 for l = 10, and 0.411 for l = 14. For series II, V_m^E of {x1,4-C₄H₈Cl₂ + (1 ? x)n-C₇H₁₆} is small and S-shaped, the maximum being situated at x_max = 0.178 with V_m^E(x_max)/(cm³ · mvl^?1) = 0.095, and the minimum is at x_min = 0.772 with V_m^E(x_min)/(cm³ · mol^?1) = ?0.087. The excess volumes of the other mixtures are all positive and fairly large: at x = 0.5, V_m^E/(cm³ · mol^?1) is 0.458 for l = 10, and 0.771 for l = 14. The C_{p, m}^Es of series I are all negative and |C_{p, m}^E| increases with increasing l: at x = 0.5, C_{p, m}^E/(J · K^?1 · mol^?1) is ?0.56 for l = 7, ?1.39 for l = 10, and ?3.12 for l = 14. Two minima are observed for C_{p, m}^E of {x1,4-C₄H₈Cl₂ + (1 ? x)n-C₇H₁₆}. The more prominent minimum is situated at x′_min = 0.184 with C_{p, m}^E(x′_min)/(J · K^?1 · mol^?1) = ?0.62, and the less prominent at x″_min = 0.703 with C_{p, m}^E(x″_min)/(J · K^?1 · mol^?1) = ?0.29. Each of the remaining two mixtures (l = 10 and 14) has a pronounced minimum at low mole fraction (x_min = 0.222 and 0.312, respectively) and a broad shoulder around x = 0.7.     

Excess molar volumes of methylcyclohexane+benzene, +methylbenzene, +1,4-dioxane,and +tetrahydrofuran at 303.15 K

Excess molar volumes V_m^E as function of mole fraction x for methylcyclohexane + benzene, + methylbenzene, + 1,4-dioxane, and + tetrahydrofuran are reported at 303.15 K. The excess molar volumes are positive and indicate the presence of weak interactions.     

Excess functions of (an alkane + carbon disulphide) at 298.15 K

Vapour pressures, excess enthalpies, and densities for {(1?x)C₆H₁₄ + xCS₂} {(1?x)C₁₀H₂₂ + xCS₂}, {(1?x)C₁₃H₂₈ + xCS₂}, and {(1?x)C₁₆H₃₄ + xCS₂} have been measured at 298.15 K. It was found that H_m^E and V_m^E increase as chain length increases while G_m^E diminishes, becoming negative for hexadecane.     

Measurements of HmE and VmE for (propane + sulphurhexafluoride) in the near critical region

A flow mixing calorimeter followed by a vibrating-tube densimeter has been used to measure excess molar enthalpies H_m^E and excess molar volumesV_m^E of {xC₃H₈ +  (1  − x)SF₆}. Measurements over a range of mole fractionsx have been made at the pressure p =  4.30 MPa at eight temperatures in the rangeT =  314.56 K to 373.91 K, in the liquid region at p =  3.75 MPa andT =  314.56 K, in the two phase region at p =  3.91 MPa andT =  328.18 K, and in the supercritical region at p =  5.0 MPa andT =  373.95 K. The measurements are compared with results from the Patel–Teja equation of state which reproduces the main features of the excess function curves as well as it does for similar measurements on{xCO₂ +  (1  − x)C₂H₆} ,{xCO₂ +  (1  − x)C₂H₄} and{xCO₂ +  (1  − x)SF₆} reported previously.     

Thermodynamics of liquid mixtures of argon+ carbon monoxide

The heat of mixing of liquid argon (component 1) and liquid carbon monoxide has been measured by direct calorimetry for several mixtures of composition ranging from x₁ ? 0.2 to x₁ ? 0.8 at 85.79 K. At this temperature H^E is positive and an almost parabolic function of mole fraction, with a maximum value of H^E = 95.9 J mol^?1 at x₁ = 0.569.The experimental results are compared with those derived from the Gibbons-Rigby equation of state, and from conformal solution theory.     

Excess molar volumes of (cyclohexanone+trichloromethane,or 1,2-dichloroethane,or trichloroethene,or 1,1,1-trichloroethane,or cyclohexane) at T=308.15 K,and of (cyclohexanone+dichloromethane) at T=303.15 K

Excess molar volumes V_m^E have been measured using a dilatometric technique for mixtures of cyclohexanone (C₆H₁₀O) with trichloromethane (CHCl₃), 1,2-dichloroethane (CH₂ClCH₂Cl), trichloroethene (CHClCCl₂), 1,1,1-trichloroethane (CCl₃CH₃), and cyclohexane (c-C₆H₁₂) at T=308.15 K, and for cyclohexanone+dichloromethane (CH₂Cl₂) at T=303.15 K. Throughout the entire range of the mole fraction χ of C₆H₁₀O, V_m^E has been found to be positive for χ C₆H₁₀O+(1−χ)c-C₆H₁₂, and negative for χ C₆H₁₀O+(1−χ)CH₂Cl₂, χ C₆H₁₀O+(1−χ)CHClCCl₂, χ C₆H₁₀O+(1−χ)CHCl₃, and χ C₆H₁₀O+(1−χ) CCl₃CH₃. For χ C₆H₁₀O+(1−χ)CH₂ClCH₂Cl, V_m^E has been found to be positive at lower values of χ and negative at high values of χ, with inversion of sign from positive to negative values of V_m^E for this system occurring at χ∼0.78. Values of V_m^E for the various systems have been fitted by the method of least squares with smoothing equation, and have been discussed from the viewpoint of the existence specific interactions between the components.     

Vapour-liquid equilibria. X. The ternary system cyclohexane-methanol-acetone at 293.15 and 303.15 K

Total vapour pressure measurements made by the modified static method for the ternary system cyclohexanemethanolacetone and all the constituent binary systems at 293.15 and 303.15 K are presented. The alcohol high-dilution region of the cyclohexanemethanol system has been thoroughly studied. Different exprerssions for G^E suitable for correlation of these data are tested. The prediction of ternary VLE from the constituent binaries is studied. The accuracy of the prediction of H^E from two (P, x) isotherms is studied for the binary systems. The possibility of predicting the ternary H^E from VLE isotherms is also. Our results are compared with literature data.     

Near critical measurements of HmEandVmE for { xCO2 + (1 − x)SF6} and measurements made over the pressure range 2.5 to 10.0 MPa at the temperature T = 301.95 K

A flow mixing calorimeter, followed by a vibrating tube densimeter, has been used to measure excess molar enthalpies H_m^Eand excess molar volumesV_m^E of {xCO₂ +  (1  − x)SF₆}. Measurements over a range of mole fraction x have been made at the temperatures T =  302.15 K and T =  305.65 K at the pressures (3.76, 5.20, 6.20, and 7.38) MPa. The lowest pressure 3.76 MPa is close to thecritical pressure of SF₆ and the highest pressure 7.38 MPa is close to the critical pressure of CO ₂. Measurements atx =  0.5 have been made over the pressure range (2.5 to 10.0) MPa at the temperature 301.95 K. Some of the measurements are very close to the critical locus of the mixture. The measurements are compared with the Patel–Teja equation of state which reproduces the main features of the excess function curves as well as it does for similar measurements on {xCO₂ +  (1  − x)C₂H₆} and{xCO₂ +  (1  − x)C₂H₄} . The equation was used to calculate residual enthalpies and residual volumes for the pure components and for the mixture, and inspection of the way these combine to give excess enthalpies and volumes assisted the interpretation of the pressure scan measurements.     

Excess Gibbs free energies of mixtures of tetrakis(2-ethylbutoxy)silane + cyclohexane, + benzene,and + carbon tetrachloride at 308.15 K

The excess Gibbs free energies G^E for tetra(2-ethylbutoxy)silane (tkebs) + cyclohexane, + benzene, and + carbon tetrachloride have been measured at 308.15 K with a new vapour-pressure apparatus. For tkebs + cyclohexane, G^E is negative with a minimum value of ?538 J mol^?1 near x₂(tkebs) = 0.39. For tkebs + benzene, the minimum value of G^E is ?453 J mol^?1 near x₂ = 0.41, and for tkebs + carbon tetrachloride, G^E has a minimum value of ?715 J mol^?1 near x₂ = 0.39.     

Excess thermodynamic properties of binary mixtures of N,N-dimethylacetamide with water or water-d2 at temperatures from 277.13 K to 318.15 K

Densities of binary mixtures of N,N-dimethylacetamide (DMA) with water (H₂O) or water-d₂ (D₂O) were measured at the temperatures from T=277.13 K to T=318.15 K by means of a vibrating-tube densimeter. The excess molar volumes V_m^E, calculated from the density data, are negative for the (H₂O + DMA) and (D₂O + DMA) mixtures over the entire range of composition and temperature. The V_m^E curves exhibit a minimum at x(DMA)≅0.4. At each temperature, this minimum is slightly deeper for the (D₂O + DMA) mixtures than for the corresponding (H₂O + DMA) mixtures. The difference between D₂O and H₂O systems becomes smaller when the temperature increases. The V_m^E results were correlated using a modified Redlich–Kister expansion. The partial molar volume of DMA plotted against x(DMA) goes through a sharp minimum in the water-rich region around x(DMA)≅0.08. This minimum is more pronounced the lower the temperature and is deeper in D₂O than in H₂O at each temperature. Again, the difference becomes smaller as the temperature increases. The excess expansion factor α^E plotted against x(DMA) exhibit a maximum in the water rich region of the mole fraction scale. At each temperature, this maximum is higher for the (D₂O + DMA) mixtures than for the corresponding (H₂O + DMA) mixtures, and the difference becomes smaller as the temperature increases. At its maximum, α^E can be even more than 25 per cent of total value of the cubic expansion coefficient α in the (H₂O + DMA) and (D₂O + DMA) mixtures.     

Near critical measurements of HmE andVmE for (ethane + sulphur hexafluoride)

A flow mixing calorimeter and a vibrating-tube densimeter have been used to measure excess molar enthalpies H_m^E and excess molar volumes V_m^E of {xC₂H₆ +  (1  − x)SF₆ }. Measurements over a range of mole fractions x have been made at T =  305.65 K and T =  312.15 K and at the pressures (3.76, 4.32, 4.88 and 6.0) MPa. The pressure 3.76 MPa is close to the critical pressure of SF₆, the pressure 4.88 MPa is close to the critical pressure of C₂H₆, and the pressure 4.32 MPa is midway between these values. The measurements are compared with the Patel–Teja equation of state which reproduces the main features of the excess function curves as well as it does for similar measurements on {xCO₂ +  (1  − x)C₂H₆ }, {xCO₂ +  (1  − x)C₂H₄ } and {xCO₂ +  (1  − x)SF₆ }.     

Thermodynamics of the amalgam cells {M-Amalgam|MCl or MCl2 (m)|AgCl|Ag} (M=Rb,Cs, Sr,Ba) and primary medium effects in (acetonitrile + water)

The potential difference E of the amalgam cell {M_xHg_1 − x|MCl or MCl₂ (m)| AgCl |Ag} (M=Rb, Cs, Sr, Ba) has been measured as a function of the mole fraction x_M of M metal in amalgams and of the molality m of MCl (or MCl₂) in (acetonitrile [A] + water [W]) solvent mixtures containing up to acetonitrile mass fraction w_A=0.50, at T=298.15 K. The respective molal-scale standard potential differences E^∘_m have been determined together with the relevant activity coefficients γ_± functions of the MCl (or MCl₂) molality. The E^∘_m dependence on the mole fraction x_A of acetonitrile in the solvent mixture within the range explored turns out to be linear for all the four metals M in the amalgams considered. Of course, also the difference ([E^∘_m]_W−[E^∘_m]_A), which is a measure of the primary medium effect upon transferring MCl (or MCl₂) from pure water [W] to the acetonitrile [A] mixture, is linear in x_A.In this context, following Feakins and French's scheme, which implies volume fraction statistics, analysis of the relevant mol · dm⁻³ scale primary medium effects, i.e., ([E^∘_c]_W−[E^∘_c]_A), upon MCl (or MCl₂), as a linear function of the logarithm of water volume fraction, would lead to primary hydration numbers of 4.2 for RbCl, 4.0 for CsCl, 10.7 for SrCl₂, and 10.3 for BaCl₂, respectively, in acceptable agreement with literature data by Bockris based on different methods.     

Solubility Determination,Hansen Solubility Parameters and Thermodynamic Evaluation of Thymoquinone in (Isopropanol + Water) Compositions

This article studies the solubility, Hansen solubility parameters (HSPs), and thermodynamic behavior of a naturally-derived bioactive thymoquinone (TQ) in different binary combinations of isopropanol (IPA) and water (H₂O). The mole fraction solubilities (x₃) of TQ in various (IPA + H₂O) compositions are measured at 298.2–318.2 K and 0.1 MPa. The HSPs of TQ, neat IPA, neat H₂O, and binary (IPA + H₂O) compositions free of TQ are also determined. The x₃ data of TQ are regressed by van’t Hoff, Apelblat, Yalkowsky–Roseman, Buchowski–Ksiazczak λh, Jouyban–Acree, and Jouyban–Acree–van’t Hoff models. The maximum and minimum x₃ values of TQ are recorded in neat IPA (7.63 × 10⁻² at 318.2 K) and neat H₂O (8.25 × 10⁻⁵ at 298.2 K), respectively. The solubility of TQ is recorded as increasing with the rise in temperature and IPA mass fraction in all (IPA + H₂O) mixtures, including pure IPA and pure H₂O. The HSP of TQ is similar to that of pure IPA, suggesting the great potential of IPA in TQ solubilization. The maximum molecular solute-solvent interactions are found in TQ-IPA compared to TQ-H₂O. A thermodynamic study indicates an endothermic and entropy-driven dissolution of TQ in all (IPA + H₂O) mixtures, including pure IPA and pure H₂O.     

The effect of temperature and pressure on the protonation ofo-phosphate ions at 348.15 and 398.15 K,and at 1.52 and 12.50 MPa

Flow calorimetry has been used to study the interaction of HPO ₄ ^2– and H₂PO ₄ ^– with H⁺ in water at temperatures of 348.15 and 398.15 K and at pressures of 1.52 and 12.50 MPa. The protonations of HPO ₄ ^2– and H₂PO ₄ ^– are exothermic and endothermic, respectively, under these experimental conditions. Under the conditions of this study, the effect of pressure on the enthalpy changes for both reactions is small. Equilibrium constant K, enthalpy change H, and entropy change S values are given for the protonation reactions at each temperature. These values are compared with those reported in the literature. Incorporation into the calculation procedure of reactions involving association between protonated phosphate species to form hydrogen-bonded dimers does not result in better fits of the experimental data.     

Excess molar enthalpies and excess molar heat capacities of (2-butanone + cyclohexane,or methylcyclohexane,or benzene,or toluene,or chlorobenzene,or cyclohexanone) atT = 298.15 K

Excess molar enthalpies of (2- butanone  +  cyclohexane, or methylcyclohexane, or toluene, or chlorobenzene, or cyclohexanone) and excess molar heat capacities of (2- butanone  +  benzene, or toluene, or chlorobenzene, or cyclohexanone) were measured atT =  298.15 K. Aliphatic systems were endothermic and the chlorobenzene system was exothermic. On the other hand, the toluene system changed sign to be S-shaped similar to the benzene system reported by Kiyohara et al. The values of excess molar enthalpies of the present mixtures were slightly larger than the corresponding mixtures of cyclohexanone already reported. Excess molar heat capacities of aromatic systems were characteristically S-shaped for the mixture containing aromatics. The values of the present mixtures were less than the corresponding mixtures of cyclohexanone. The mixture (2-butanone  +  cyclohexanone) was endothermic forH_m^E and negative for C_p,m^E.     

Excess molar enthalpies of triethylamine + ethylbenzene, + n-propylbenzene, + n-butylbenzene, + isopropylbenzene,and + isobutylbenzene at 303.15 K

Excess molar enthalpies H_m^E of triethylamine + ethylbenzene, + n-propylbenzene, + n-butylbenzene, + isopropylbenzene, and + isobutylbenzene were measured over the entire composition range at 303.15 K with an LKB flow microcalorimeter. H_m^E values are positive and decrease with increasing chain length of the alkylbenzene.     

The enthalpies of solution of DL-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution (298.15 K) of DL-α-alanine in water-organic solvent mixtures were measured at organic component concentrations x ₂ = 0–0.4 mole fractions. The organic solvents used were acetonitrile (ACN), formamide (FA), N,N-dimethylformamide (DMFA), and N,N-dimethylsulfoxide (DMSO). The standard enthalpies of solution Δ_sol H ^o, solvation Δ_solv H ^o, and transfer (Δ_tr H ^o) of DL-α-alanine from water to mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on solute thermochemical characteristics was considered. The solution of DL-α-alanine in the mixtures studied was endothermic over the whole range of organic component concentrations. The Δ_sol H ^o, Δ_tr H ^o, and Δ_solv H ^o values as functions of x ₂ can pass extrema (DMSO and DMFA), be almost independent of mixed solvent composition (FA), or be exothermic and monotonic functions (ACN). The enthalpy coefficients of pair interactions (h _xy ) between DL-α-alanine and organic solvent molecules were calculated. The linear Kamlet-Taft equation was used to correlate the h _xy values with the properties of organic solvents.     

Excess thermodynamic parameters of binary mixtures of methanol,ethanol, 1-propanol,and 2-butanol + chloroform at (288.15–323.15 K) and comparison with the Flory theory

In this work we used the experimental result for calculating the thermal expansion coefficients α, and their excess values α ^E , and isothermal coefficient of pressure excess molar enthalpy and comparison the obtain results with Flory theory of liquid mixtures for the binary mixtures {methanol, ethanol, 1-propanol and 2-butanol-chloroform} at 288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15 K. The excess thermal expansion coefficients α ^E and the isothermal coefficient of pressure excess molar enthalpy ((∂H _m^E/∂P) _T,x for binary mixtures of {methanol and ethanol + chloroform} are S-shaped and for binary mixtures of {1-propanol and 2-butanol + chloroform} are positive over the mole fraction. The isothermal coefficient of pressure excess molar enthalpy (∂H _m^E/∂P) _T,x , are negative over the mole fraction range for binary mixture of {1-propanol and 2-butanol + chloroform}. The calculated values by using the Flory theory of liquid mixtures show a good agreement between the theory and experimental.