The standard Gibbs free energy of formation of calcium chromium (III) oxide in the temperature range (1073 to 1273) K

The standard molar Gibbs free energy of formation of CaCr₂O₄ from CaO and Cr₂O₃ has been determined by the e.m.f. measurement of galvanic cells involving a single crystal CaF₂ and a polycrystalline CaZrO₃ solid-state electrolytes in the temperature range (1073 to 1273) K. Reproducible e.m.f. values were obtained. The average values of the standard molar enthalpy and the standard molar entropy in the temperature range covered by the e.m.f. measurements have been also estimated. The results have been compared with those obtained by other authors.     

Isothermal (vapour + liquid) equilibria and excess Gibbs free energies in some binary (cyclopentanone + chloroalkane) mixtures at temperatures from 298.15 K to 318.15 K

The vapour pressures of binary (cyclopentanone + 1-chlorobutane, +1,3-dichloropropane, and +1,4-dichlorobutane) mixtures, were measured at the temperatures of (298.15, 308.15, and 318.15) K. The vapour pressures vs. liquid phase composition data have been used to calculate the excess molar Gibbs free energies G^E of the investigated systems, using Barker’s method. Redlich–Kister, Wilson and NRTL equations, taking into account the vapor phase imperfection in terms of the second virial coefficient, have represented the G^E values. No significant difference between G^E values obtained with these equations has been observed.     

(Vapour + liquid) equilibria and excess Gibbs free energies of (cyclohexanone + 1-chlorobutane and + 1,1,1-trichloroethane) binary mixtures at temperatures from (298.15 to 318.15) K

The vapour pressures of binary (cyclohexanone + 1-chlorobutane, + 1,1,1-trichloroethane) mixtures were measured at the temperatures of (298.15, 308.15, and 318.15) K. The vapour pressures vs. liquid phase composition data have been used to calculate the excess molar Gibbs free energies G^E of the investigated systems, using Barker’s method. Redlich–Kister, Wilson, UNIQUAC, and NRTL equations, taking into account the vapour phase imperfection in terms of the 2-nd virial coefficient, have represented the G^E values. No significant difference between G^E values obtained with these equations has been observed.     

Densities of {poly(ethylene glycol) + water} over the temperature range (283.15 to 363.15) K

Densities of {poly(ethylene glycol) [PEG] + water} prepared with PEG average molar mass (200, 400, 600, and 1500) g · mol^?1 have been measured over the entire composition range over the temperature range (283.15 to 363.15) K at 10 K intervals using a density meter based on electromagnetically-induced oscillations of a U-shaped glass tube and an inbuilt Peltier thermostat. The density versus temperature data of (PEG + water) at each composition for all PEGs were fit to a simple quadratic equation: ρ/(g · cm^?3) = ρ₀/(g · cm^?3) + a(T/K) + b(T/K)². Fits were observed to be satisfactory at each composition for all four (PEG + water). The excess molar volumes of (PEG + water) are observed to be negative and significant over the entire composition range for all four (PEG + water). Irrespective of the temperature, the maximum absolute excess molar volumes are observed in the water-rich region of the mixture and are found to decrease with increasing temperature. This is attributed to the presence of strong interactions within the (PEG + water). Specifically, it is proposed to be due to the H-bonding interactions between the PEG and the water molecules within the mixtures.     

(p, ρ, T) Properties for n-butane in the temperature range from 280 K to 380 K at pressures up to 200 MPa

The (p, ρ, T) properties for n-butane in the compressed liquid phase were measured by means of a metal-bellows variable volumometer in the temperature range from 280 K to 380 K at pressures up to 200 MPa. The mole fraction purity of the n-butane used in the measurements was 0.9997. The expanded uncertainties (k = 2) in temperature, pressure, and density measurements have been estimated to be less than ±3 mK; 1.4 kPa (p ⩽ 7 MPa), 0.06% (7 MPa < p ⩽ 50 MPa), 0.1% (50 MPa < p ⩽ 150 MPa), and 0.2% (p > 150 MPa); and 0.09%, respectively. In the region above100 MPa at T = 280 K and T = 440 K, the uncertainty in density measurements increases from 0.09% to 0.13% and 0.22%, respectively. Eight (p, ρ, T) measurements at the same temperatures and pressures as the literature values have been conducted for comparisons. In addition, comparisons of the available equations of state with the present measurements are reported.     

Determination of the activities in the (Ni + Al) alloys in the temperature range 870 K to 920 K by a solid-state galvanic cell using a CaF2 electrolyte

The activities of aluminium and nickel are constituents in the (Ni + Al) superalloys in the concentration range 50 mol% to 70 mol% of Al at the temperatures (870, 900, and 920) K were determined with the help of solid-state galvanic cells involving calcium fluoride as an electrolyte. The partial molar Gibbs free energies of aluminium and nickel in the alloys, and the Gibbs free energy of mixing were calculated from the e.m.f. data. The values of the standard Gibbs free energies of formation of the intermetallic compounds NiAl, Ni₂Al₃, and NiAl₃ are also given.     

Excess Gibbs energies and excess molar volumes for binary mixtures: (2-pyrrolidone + water), (2-pyrrolidone + methanol), and (2-pyrrolidone + ethanol) at the temperature 313.15 K

Total vapour pressures and excess molar volumes, measured at the temperature 313.15 K, are reported for three binary mixtures (2-pyrrolidone + water), (2-pyrrolidone + methanol) and (2-pyrrolidone + ethanol). The results are compared with previously obtained data for binary mixtures (amide + A), where amide=N-methylformamide, N,N-dimethylformamide and N-methylacetamide, and A= water, methanol, and ethanol.     

Excess Gibbs free energies of the binary mixtures of acetonitrile with butanols at 94.83 kPa

Bubble point temperatures at 94.83 kPa, over the entire composition range, are measured for the binary mixtures of acetonitrile with: n-, iso-, sec- and tert-butanols – using a Swietoslawski type ebulliometer. The liquid phase composition versus bubble point temperature measurements are found to be well represented by the Wilson model. Measured values of the liquid phase mole fraction versus bubble point temperature data are presented along with the computed values of the vapor phase mole fractions, activity coefficients and excess Gibbs free energies and discussed.     

Heat capacity (Cp) and entropy of olivine-type LiFePO4 in the temperature range (2 to 773) K

The heat capacity of olivine-type lithium iron phosphate (LiFePO₄ – LFP) has been measured covering a temperature range from (2 to 773) K. Three different calorimeters were used. The Physical Property Measurement System (PPMS) from Quantum Design was applied in the range between T = (2 and 300) K, a Micro-DSC II from Setaram within the range between T = (283 and 353) K and data between T = (278 and 773) K were measured by means of a Sensys DSC (Setaram) using the Cp-by-step method. Experimental data are given with an error of (1 to 2)% above T = 20 K and up to 8% below 20 K. The data were subdivided into appropriate temperature intervals and fitted using common heat capacity functions. The low temperature results permit the calculation of standard entropies and temperature coefficients of electronic, lattice, as well as magnetic (antiferromagnetic transition at T = 49.2 K) contributions to the heat capacity. The obtained experimental values were compared to results of a recently published first principles phonon study (DFT) and to few available experimental data from the literature.     

Densities and volume properties of (water + tert-butanol) over the temperature range of (274.15 to 348.15) K at pressure of 0.1 MPa

The densities of {water (1) + tert-butanol (2)} binary mixture were measured over the temperature range (274.15 to 348.15) K at atmospheric pressure using “Anton Paar” digital vibrating-tube densimeter. Density measurements were carried out over the whole concentration range at (308.15 to 348.15) K. The following volume parameters were calculated: excess molar volumes and thermal isobaric expansivities of the mixture, partial molar volumes and partial molar thermal isobaric expansivities of the components. Concentration dependences of excess molar volumes were fitted with Redlich–Kister equation. The results of partial molar volume calculations using four equations were compared. It was established that for low alcohol concentrations at T ? 208 K the inflection points at x₂ ≈ 0.02 were observed at concentration dependences of specific volume. The concentration dependences of partial molar volumes of both water and tert-butanol had extremes at low alcohol content. The temperature dependence of partial molar volumes of water had some inversion at х₂ ≈ 0.65. The temperature dependence of partial molar volumes of tert-butanol at infinite dilution had minimum at ≈288 K. It was discovered that concentration dependences of thermal isobaric expansivities of the mixture at small alcohol content and low temperatures passed through minimum.     

Measurements of (p, ρ, T) properties for isobutane in the temperature range from 280 K to 440 K at pressures up to 200 MPa

Measurements of (p, ρ, T) properties for isobutane in the compressed liquid phase have been obtained by means of a metal-bellows variable volumometer in the temperature range from 280 K to 440 K at pressures up to 200 MPa. The volume-fraction purity of isobutane used was 0.9999. The expanded uncertainties (k = 2) of temperature, pressure, and density measurements have been estimated to be less than 3 mK, 1.5 kPa (p ⩽ 7 MPa), 0.06% (7 MPa < p ⩽ 50 MPa), 0.1% (50 MPa < p ⩽ 150 MPa), and 0.2% (p > 150 MPa), and 0.11%, respectively. In region more than 100 MPa at 280 K and 440 K, the uncertainty in density measurements rise up to 0.15% and 0.23%, respectively. The differences of the present density values at the same temperature between two series of measurements, in which the sample fillings are different, are within the maximum deviation of 0.09% in density, which is enough lower than the expanded uncertainty in density. Eight (p, ρ, T) measurements at the same temperatures and pressures as the literature values have been conducted for comparison. In addition, vapour pressures were measured at T = (280, 300) K. Moreover, the comparisons of the available equations of state with the present measurements are reported.     

Thermodynamic investigation of methyl salicylate/1-pentanol binary system in the temperature range from 278.15 K to 303.15 K

Densities (ρ), speeds of sound (u), isentropic compressibilities (k_s), refractive indices (n_D), and surface tensions (σ) of binary mixtures of methyl salicylate (MSL) with 1-pentanol (PEN) have been measured over the entire composition range at the temperatures of 278.15 K, 288.15 K, and 303.15 K. The excess molar volumes (V^E), excess surface tensions (σ^E), deviations in speed of sound (Δu), deviations in isentropic compressibility (Δk_s), and deviations in molar refraction (ΔR) have been calculated. The excess thermodynamic properties V^E, σ^E, Δu, Δk_s, and ΔR were fitted to the Redlich–Kister polynomial equation and the A_k coefficients as well as the standard deviations (d) between the calculated and experimental values have been derived. The surface tension (σ) values have been further used for the calculation of the surface entropy (S^S) and the surface enthalpy (H^S) per unit surface area. The lyophobicity (β) and the surface mole fraction $(x_2^{\text{S}})$ of the surfactant component PEN have been also derived using the extended Langmuir model. The results provide information on the molecular interactions between the unlike molecules that take place at the surface and the bulk.     

Determination of the standard Gibbs free energies of formation of the silicates of cobalt,magnesium, and strontium by e.m.f. measurements

Standard Gibbs free energies of formation of the silicates in the quasi-binaries: CoO and SiO₂, MgO and SiO₂, and SrO and SiO₂ were determined with the help of solid-state galvanic cells in the temperature ranges 1273 to 1673 K, 1373 to 1573 K, and 1323 to 1473 K, respectively. Stabilized ZrO₂ was used as an electrolyte for the CoO and SiO₂ system. For the MgO and SiO₂ system MgF₂, and for the SrO and SiO₂ system SrF₂, was used as an electrolyte embedded in a silicate-matrix phase.     

Thermodynamic properties of solutions of sodium di-hydrogen phosphate in (1-propanol + water) mixed-solvent media over the temperature range of (283.15 to 303.15) K

The apparent molar volume and apparent molar isentropic compressibility of solutions of sodium di-hydrogen phosphate (NaH₂PO₄) in (1-propanol + water) mixed-solvent media with alcohol mass fractions of 0.00, 0.05, 0.10, and 0.15 are reported over the range of temperature (283.15 to 303.15) K at 5 K intervals. The results were fitted to a Redlich–Mayer type equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at the infinite dilution were also calculated at the working temperature. The results show a positive transfer volume of NaH₂PO₄ from an aqueous solution to an aqueous 1-propanol solution. The apparent molar isentropic compressibility of NaH₂PO₄ in aqueous 1-propanol solutions is negative and it increases with increasing the concentration of NaH₂PO₄, 1-propanol, and temperature. Electrical conductivity and refractive index of the solutions are also studied at T = 298.15 K. The effects of the electrolyte concentration and relative permittivity of the medium on the molar conductivity were also investigated.     

Rheological behaviour of some saccharides in aqueous potassium chloride solutions over temperature range (288.15 to 318.15) K

The viscosities, η of mono-, di-, tri-saccharides and methylglycosides, viz., d(+)-xylose (XYL), d(?)-arabinose (ARA), d(?)-ribose (RIB), d(?)-fructose (FRU), d(+)-galactose (GAL), d(+)-mannose (MAN), d(+)-glucose (GLU), d(+)-melibiose (MEL), d(+)-cellobiose (CEL), d(+)-lactose monohydrate (LAC), d(+)-maltose monohydrate (MAL), d(+)-trehalose dihydrate (TRE), sucrose (SUC), d(+)-raffinose pentahydrate (RAF), α-methyl-d(+)-glucoside (α-Me-GLU), methyl-α-d-xylopyranoside (Me-α-XYL), and methyl-β-d-xylopyranoside (Me-β-XYL) in water and in (0.5, 1.0, 2.0, and 3.0) mol · kg^?1 aqueous solutions of potassium chloride (KCl) have been determined at T = (288.15, 298.15, 308.15, and 318.15) K from efflux time measurements by using a capillary viscometer. Densities used to determine viscosities have been reported earlier. The viscosity data have been utilized to determine the viscosity B-coefficients employing the Jones–Dole equation at different temperatures. From these data, the viscosity B-coefficients of transfer, Δ_tB have been estimated for the transfer of various saccharides/methylglycosides from water to aqueous potassium chloride solutions. The Δ_tB values have been found to be positive, whose magnitude increases with the increase in concentration of potassium chloride in all cases. The dB/dT coefficients, pair, η_AB and triplet, η_ABB viscometric interaction coefficients have also been determined. Gibbs free energies of activation and related thermodynamic parameters of activation of viscous flow have been determined employing Feakin’s transition-state theory. The signs and magnitudes of various parameters have been discussed in terms of solute–solute and solute–solvent interactions occurring in these solutions. The effect of substitution of –OH by methoxy group, –OCH₃ has also been discussed.     

Water activities of ternary mixtures of poly(ethylene glycol), NaCl and water over the temperature range of 293.15 K to 313.15 K

The improved isopiestic method has been used to obtain activities of water for aqueous solutions of poly(ethylene glycol) 400/NaCl at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K. From these measurements, values of the vapour pressure of solutions were determined. The effect of temperature on the (vapour + liquid) equilibrium of {poly(ethylene glycol) + NaCl + H₂O} systems has been studied. It was found that the slope of the constant activity lines for water increased with increasing temperature. The results have been discussed on the basis of the effect of temperature on the hydrophobicity of the polymer. Also it was found that the vapour pressure depression for an aqueous (PEG + NaCl) system is more than the sum of those for the corresponding binary solutions. Furthermore, the segment-based local composition Wilson model has been used for the correlation of the experimental water activity data. The agreement between the correlation and the experimental data are good.     

(Vapour + liquid) equilibrium in (N,N-dimethylacetamide + ethanol + water) at the temperature 313.15 K

Total vapour pressures, measured at the temperature 313.15 K, are reported for the ternary mixture (N,N-dimethylacetamide + ethanol + water), and for binary constituent (N,N-dimethylacetamide + ethanol). The present results are also compared with previously obtained data for (amide + ethanol) binary mixtures, where amide = N-methylformamide, N,N-dimethylformamide, N-methylacetamide, 2-pyrrolidinone, and N-methylpyrrolidinone. We found that excess Gibbs free energy of mixing for binary (amide + ethanol) mixtures varies roughly linearly with the molar volume of amide.