Enthalpies of mixing of fused salts

Starting from our previously proposed model of fused alkali metal halides, we discuss the processes involved in the mixing of fused alkali metal halides and dissolution (mixing) of TiCl₄(g)[ZrCl₄(liq)] in fused alkali metal halides and their mixtures. The resulting quantities are compared with the experimental. They vary with changes in the radius of the salt-solvent cation in the same direction as the experimental values. The dissolution of KCl_z in mixtures of fused alkali metal halides was considered from the point of view of the energy nonuniformity of the Me₁ ⁺ and Me₂ ⁺ cations.It was shown that the experimentally observed increase in the enthalpy of mixing with increasing radius of the cation of the salt-solvent is caused not so much by a change in the bond energies of the KCl _n ^z–n complexes in various media, as by a change in the bond energies of complex MeCl ₄ ^3– anions of the solvent.     

Enthalpies of mixing of liquid alloys in the In-Pd-Sn system and the limiting binary systems

The partial and integral enthalpies of mixing of molten binary In-Pd (up to about 29 at.% Pd), In-Sn (entire compositional range) and Pd-Sn (up to about 53 at.% Pd) alloys were determined at 900 °C. A Calvet-type microcalorimeter was used for the measurements employing a drop calorimetric technique. Additionally, five sections in the ternary In-Pd-Sn system (compositions up to about 40 at.% Pd) were investigated at 900 °C. The ternary interaction parameters were fitted using the Redlich-Kister-Muggiano model for substitutional solutions. The isoenthalpy curves for In-Pd-Sn at 900 °C were constructed for the integral molar enthalpy of mixing. Furthermore, the experimental results in the ternary system were compared with calculated values obtained by employing different binary extrapolation models.     

Enthalpies of mixing of binary and ternary mixtures containing diisopropylether,benzene and cyclohexane at 303.15 K

Enthalpies of mixing H have been measured for liquid binary mixtures of diisopropylether (DIPE)+benzene or cyclohexane and for liquid ternary mixtures diisopropylether+benzene+cyclohexane at 303.15 K and constant pressure using a C80 calorimeter. A Redlich-Kister type equation was used to correlate experimental results.     

Enthalpies of mixing of acetonitrile with isomeric butanols: Enthalpies of hydrogen-bonded complexes

The enthalpies of mixing of four isomeric butanols with acetonitrile were determined at 30°C by a Calvet type microcalorimeter. All the four systems showed endothermic behaviour. The enthalpies of hydrogen bonded complex formation were determined by means of a thermochemical cycle. 1-butanol formed a stronger bonding (−13kJ/mole) than the other three isomers (−11.20kJ/mole). The strength of the H-bond of alcohol with C ≡ N is much less than that with C-N. NCL communication no. 4883     

Enthalpies of formation of solid cobalt-tellurium alloys

The enthalpies of formation of solid Co?Te alloys were determined at room temperature with an isoperibol solution calorimeter of the submarine type. Co?Te alloys and mechanical mixtures of the pure components were dissolved in separate experiments in a saturated hydrochloric acid (8.000n)—bromine mixture and the enthalpies of formation obtained by difference. For the NiAs-type β-phase ΔH _f ^o(N_Te)=(4.079–15.017N _Te) kcal·g-atom^?1 and for the marcasitetype γ-phase ΔH _f ^o(N _Te)=(3.787–14.400N _Te) kcal·g-atom^?1. Combining these results with data from the literature integral thermodynamic properties of solid Co—Te alloys were calculated at room temperature and at 600°C.     

Enthalpies of formation of gaseous Zintl-molecules over sodium-tellurium alloys

The vapor over sodium-tellurium alloys was investigated using Knudsen effusion mass spectrometry. The stoichiometries of the molecules in the gas phase are compared with the stoichiometries of those appearing in liquid ammonia. Enthalpies of formation for the gaseous molecules are obtained using van't Hoff plots and third law evaluations.     

Enthalpies of formation of solid nickel-gallium and nickel-germanium alloys

Tin solution calorimetry has been used to measure the enthalpies of formation of the solid phases of the nickel-gallium system at 300 K and of the nickel-germanium system at 330 K. Values are reported for the two nickel-rich binary solid solutions and for the intermediate phases Ni₃Ga, Ni₂Ga, Ni₃Ga₂, NiGa, Ni₂Ga₃, Ni₃Ga₇, Ni₃Ge, Ni₂Ge and NiGe. These and previously determined enthalpies of formation of related palladium alloy compounds are compared and factors affecting the bonding mechanisms are discussed; a dependence of intercomponent transfer upon electron concentration and electronegativity differences is suggested by a re-examination of the intermediate phase data.     

Enthalpies of mixing of some aqueous electrolytes at 373.15 K

The enthalpies of mixing of a variety of aqueous electrolytes at an ionic strength of 1.000 mol·kg^?1 have been measured at 373.15 K. The mixtures studied were LiBr + KBr, NaBr + KBr, KBr + (C₄H₉)₄NBr, NaCl + Na₂SO₄, NaCl + MgCl₂, MgSO₄ + Na₂SO₄, MgCl₂ + MgSO₄, NaCl + MgSO₄, and MgCl₂ + Na₂SO₄. In contrast to most previous enthalpies of mixing of alkali halides, the mixtures with multivalent ions studied here often have large temperature dependences. The results for the mixtures involving MgSO₄ are consistent with a higher degree of ion pairing as the temperature increases. The present measurements, together with Gibbs energies of mixing at 298.15 K, allow the calculation of Gibbs energies of mixing at the higher temperature. This appears to be the most accurate and convenient method available for determining Gibbs energies of mixing at high temperatures.     

Enthalpies of mixing of di- n -butyl ether with isomeric butanols: Enthalpies of hydrogen-bonded complexes

The enthalpies of mixing of four isomeric butanols with di-n-butyl ether were determined at 30°C by a Calvet type microcalorimeter. All the four systems showed endothermic behaviour. The enthalpies of complex formation were calculated by the thermochemical cycle. The strength of H-bonding decreases in the order l-butanol, l-methyl-1-propanol, 2-methyl-2-propanol, 2-butanol. The results are explained on the basis of a steric effect on interaction. NCL Communication No. 4430.     

Enthalpies of mixing in the iron-manganese system by direct reaction calorimetry

Integral enthalpies of mixing of solid iron—manganese alloys have been obtained at 1443K, 1073K and 873K using a modified Dench-type calorimeter. The modifications in calorimetric technique required to cope with the high volatility of manganese are described. Results are presented and discussed.Dedicated to Prof. Dr.Kurt L. Komarek on the occasion of his 60th birthday on 23rd June 1986.     

Enthalpies of mixing predicted using molecular dynamics simulations and OPLS force field

Enthalpy of mixing (EOM) is one of the most basic thermodynamic properties of mixtures. To assess feasibility of predicting EOM using force field simulation methods, fifteen (15) representative binary mixtures were investigated using MD simulations based on OPLS and TIP4P force fields. The simulation conditions and errors were carefully examined. The precision level of 0.04 kJ/mol was obtained for calculated EOM data. However, the predictions, measured by deviations from experimental data, were only qualitatively correct. Among various factors influencing the accuracy of predictions, force field quality representing interactions among different molecules plays the most significant role. Using methanol/benzene and ethanol/benzene as examples, we demonstrated that non-additive interaction terms between polarizable atoms can be used to significantly improve the quality of predictions. In addition, it appears that charge-dependent LJ parameters are required in order to represent the polarization effects accurately.     

Enthalpies of mixing of some nitriles aqueous solutions with dodecylsurfactants micellar solutions

The enthalpies of mixing of some n-nitriles (from acetonitrile to valeronitrile) aqueous solutions with dodecyltzimethylammonium bromide, sodium dodecylsulfate and dodecyltzimethylammonium oxide micellar solutions were determined. The measurements were performed by systematically changing the surfactant concentration at a given solute concentration. The experimental enthalpies were rationalized in terms of the standard enthalpy of transfer of solute from the aqueous to the micellar phase and of the distribution constant between the two phase. Information on the effect of the nature of the surfactant on the standard thermodynamic quantities of transfer(G _t ^o , H _t ^o , TS _t ^o ) is reported. The present data are compared to those previously reported for primary alcohols and the solubilizing properties shown by the different types of micelles are discussed.     

Enthalpies of mixing of water withN,N-disubstituted amides of aliphatic carboxylic acids

The enthalpies of mixing ofN,N-dialkylpropionamides with water were measured at 298.15 K. A comparative analysis of enthalpy effects (H ^E) of mixing of water withN,N-disubstituted amides of formic, acetic, and propionic acids was performed. It was established that theH ^E values depend on the length of theN,N-alkyl substituents and the size of acidic radicals. The size of the nonpolar group and the electron-donor ability of amide molecules primarily affect the enthalpy of mixing. The relative electron-donor abilities of the amides were estimated by the calorimetric method. The results obtained were discussed by invoking thermochemical data for aqueous solutions of hexamethylphosphoric triamide. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1805–1810, October, 1997.     

Enthalpies of mixing of liquid systems for lead free soldering: Al-Cu-Sn system

The present work refers to high-temperature drop calorimetric measurements on liquid Al–Cu, Al–Sn, and Al–Cu–Sn alloys. The binary systems have been investigated at 973 K, up to 40 at.% Cu in case of Al–Cu, and over the entire concentrational range in case of Al–Sn. Measurements in the ternary Al–Cu–Sn system were performed along the following cross-sections: x_Al/x_Cu = 1:1, x_Al/x_Sn = 1:1, x_Cu/x_Sn = 7:3, x_Cu/x_Sn = 1:1, and x_Cu/x_Sn = 3:7 at 1273 K. Experimental data were used to find ternary interaction parameters by applying the Redlich–Kister–Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. From these, the isoenthalpy curves were constructed for 1273 K. The ternary system shows an exothermic enthalpy minimum of approx. ?18,000 J/mol in the Al–Cu binary and a maximum of approx. 4000 J/mol in the Al–Sn binary system. The Al–Cu–Sn system is characterized by considerable repulsive ternary interactions as shown by the positive ternary interaction parameters.     

Mechanical properties of high strength vanadium-base ternary alloys

High strength V-20wt.%Nb and V-10wt.%Ta base ternary alloys containing aluminium, chromium and molybdenum were studied. The fabricability and tensile properties at room temperature and in a temperature range 700–1000 °C were measured. The tensile strength values were estimated on the basis of the values for the corresponding vanadium-base binary alloys and compared with the experimental data. The estimated values are in good agreement with the experimental data. From these results, V-20wt.%Nb-5wt.%Al, V-20wt.%Nb-5wt.%Cr and V-20wt.%Nb 10wt.%Mo alloys were selected as alloys that could be recommended for their good high temperature mechanical properties.     

Thermodynamic investigations of uranium-rich binary and ternary alloys

Uranium–zirconium, uranium niobium, and uranium–zirconium–niobium alloys were synthesized by the arc melting technique and their phase transition temperatures were determined using a high temperature calorimeter. Heat capacities of U–7 wt%Zr, U–7 wt%Nb, U–5 wt%Zr–2 wt%Nb, U–3.5 wt%Nb–3.5 wt%Zr, and U–2 wt%Zr–5 wt%Nb were measured using a differential scanning calorimeter in the temperature range 303–921 K. A set of self-consistent thermodynamic functions such as entropy, enthalpy, and Gibbs energy function data for these binary and ternary alloys were reported for the first time using heat capacity data obtained in this study and required literature data.     

Enthalpies of mixing and apparent molar volumes of ethanol solution of chiral dicarboxylic acids

Enthalpies of mixing of R- and S-enantiomers of dicarboxylic acids such as 2-methylbutanedioic acid (MBA), 2-hydroxylbutanedioic acid (HBA), 2-methylpentanedioic acid (MPA) and 2-hydroxyl-2-methylbutanedioic acid (HMBA) in ethanol solution have been measured for a large range of mole fraction of heterochiral dicarboxylic acid at 298.15 K. Also densities of ethanol solution of the dicarboxylic acids were determined. Enthalpies of mixing were exothermic for all the concentrations. Enthalpic stabilization on mixing was increased with decreasing concentration of all dicarboxylic acids measured. Sequence of enthalpic stabilization on mixing was MBA mixing was MBA<DHBA<MPA<HMBA<HBS at 0.5 mass%.     

Combinatorial screening of PtTiMe ternary alloys for oxygen electroreduction

The catalytic oxygen electroreduction properties of PtTiMe (Me = Co, Cr, Cu, Fe, Mn, Mo, Ni, Pd, Ta, V, W and Zr) ternary alloys were studied using an in-house developed thin film based combinatorial high throughput method. Libraries containing discrete alloy compositions were fabricated by plasma co-sputtering and the resulting alloys were electrochemically screened by the hydrodynamic rotating disk electrode technique. Candidate catalysts were identified by comparing the activity-stability-composition relationships between the platinum titanium alloys and pure platinum standard. Among the PtTiMe alloys studied, PtTiNi, PtTiCu and PtTiV, respectively, displayed the highest catalytic oxygen electroreduction activities with a tenfold, an eightfold and a sixfold enhancement as compared to the pure platinum standard and good chemical stabilities.