Cayetano Yanes

Limiting partial molar volumes of electrolytes in dimethylformamide–water mixtures at 298.15 K

Limiting partial molar volumes of electrolytes in several water-dimethyl sulfoxide mixtures, up to xDMSO= 0.1587, have been determined from density measurements at 298.15 K. A reference electrolyte assumption (TATB) has been used in order to obtain single-ion partial molar volumes of transfer from water to DMSO–water mixtures. The influence of DMSO on ΔtV′0i of alkali metals and halide ions is negligible in the highly water-rich region (up to xDMSO≈ 0.04) except for the I– ion. However, when the DMSO composition is greater than xDMSO≈ 0.04, the variation of ΔtV′0i for alkali metals is the reverse to that of halide ions. The results are discussed on the basis of ion–solvent and solvent–solvent interactions using Conways model.

Enthalpies of dilution of some electrolytes in water at 298.15 K

Abstract The enthalpies of dilution of Ph 4 PCl, Ph 4 AsCl, NaPh 4 B and R 4 NBr (where R is ethyl, n -propyl, n -butyl and n -pentyl) have been determined by flow microcalorimetry at 298.15 K in water. From the experimental data, the relative apparent molar enthalpies φ L were calculated with the aid of an extended Debye—Huckel equation. A comparison with literature values for some R 4 NBr was made. Ph 4 PCl and Ph 4 AsCl show similar behavior, unlike that of NaPh 4 B, which may be a consequence of the effect of the Na + ion in relation to the Cl − ion.

Enthalpy of interaction of some electrolytes with dimethyl sulfoxide in water at 298.15 K

Enthalpies of mixing in water of dimethyl sulfoxide with several alkali-metal halides, Ph 4 PCl and NaPh 4 B have been determined by flow microcalorimetry at 298.15 K. Enthalpic pair interaction coefficients, h NE , of the virial expansion of the excess enthalpy were calculated. The coefficients are positive for NaF, KF, Ph 4 PCl and NaPh 4 B, and negative for the remaining alkali-metal halides. A linear correlation between h NE and the anionic radius is observed. Gibbs energy and entropic pair interaction coefficients have been calculated from literature data. Single-ion pairwise coefficients have been obtained using the tetraphenylphosphonium tetraphenylborate reference electrolyte assumption.

Enthalpy of interaction of some electrolytes with 2-methyl-2-butanol in wate at 25°C

Enthalpies of mixing in water of 2-methyl-2-butanol with several electrolytes (alkali-metal halides, tetra-n-alkylammonium bromides, Ph4PCl, Ph4AsCl and NaPh4B) have been determined by flow microcalorimetry at 25°C. Enthalpic pair interaction coefficients, hNE, of the virial expansion of the excess enthalpy were calculated. All coefficients are positive and increase as the anionic size increases in anionic series of alkali-metal halides. A linear correlation between hNE and the number of carbon atoms in the apolar group of R4NBr is observed. For alkali-metal halides coefficients hNE depend mainly on the partial desolvation of halides, and for hydrophobic electrolytes both the partial desolvation of halide ions and hydrophobic interaction are the leading factors in the value of hNE.

Calorimetric cell for the measurement of excess enthalpy of volatile liquids. Excess enthalpy of cis-9-octadecenoic acid + cyclohexane at 298.15 K

Abstract A cell for the measurement of the excess enthalpy of volatile liquids in a Microcalorimeter is described. The microcalorimeter was calibrated with n -hexane + cyclohexane at 298.15 K and tested with benzene + cyclohexane. The results obtained for cis -9-octadecenoic acid + cyclohexane at 298.15 K are reported.

Excess molar volumes and excess refractive indices of (cis-9-octadecenoic acid + n-hexane or cyclohexane or benzene or trichloroethene or tetrachloroethene) at 298.15 K

Abstract The excess molar volumes V m E and excess refractive indices n D E of { cis -9-octadecenoic (oleic) acid + n -hexane or cyclohexane or benzene or trichloroethene or tetrachloroethene}` have been determined as a function of mole fraction at atmospheric pressure and 298.15 K. The V m E are positive over the entire composition range in mixtures containing trichloroethene, negative for those with n -hexane or tetrachloroethene, and sigmoid for the others. The n D E s are positive for mixtures containing n -hexane and cyclohexane and negative for the others.

Thermodynamic functions for the transfer of naphthalene from water to mixed aqueous solvents at 298.15 k

Abstract Values of free energies Δ G t XXX , enthalpies Δ H t XXX , and entropies Δ S t XXX , of transfer of naphthalene from water to urea-water, acetonitrile-water, dimethylformamide-water and dimethylsulphoxide-water mixtures at 298.15 K in the water-rich region have been determined from solubility measurements at different temperatures. The cavity term from scaled particle theory has been used to explain qualitatively the experimental transfer free energies. We have also calculated molecular-pair interaction parameters in water for the four systems studied.

Enthalpy of interaction of tetra-n-alkylammonium bromides and CsI with dimethyl sulfoxide in water at 298.15 K

Abstract Excess enthalpies in water of dimethyl sulfoxide (DMSO) with various electrolytes (CsI, Me 4 NBr, Et 4 NBr, Pr 4 NBr, Bu 4 NBr and Pen 4 NBr) have been determined by flow microcalorimetry at 298.15 K. Enthalpic pair interaction coefficients, h NE , of the virial expansion of the mixing enthalpy were calculated. The interaction of DMSO with CsI, Me 4 NBr, Et 4 NBr gives negative and that with the remaining electrolytes gives positive coefficients. In the tetraalkylammonium series, h NE becomes increasingly positive when the number of carbon atoms in the hydrocarbon chain is increased.

Excess molar enthalpies of (cis-9-octadecenoic acid + n-hexane or benzene or trichloroethene or tetrachloroethene) at 298.15 K

Abstract The excess molar enthalpies HmE of {cis-9-octadecenoic (oleic) acid + n-hexane or benzene or tetrachloroethene or trichloroethene} have been determined as a function of mole fraction at atmospheric pressure and 298.15 K. HmEs are positive for the three first mixtures and negative for the last.