Physico-chemical properties of some electrolytes in water and aqueous sodiumdodecyl sulfate solutions at different temperatures

The viscosities of some mineral salt viz.; potassium chloride, potassium nitrate, magnesium chloride, magnesium nitrate, at different concentrations have been determined in water and in binary aqueous solution of sodiumdodecyl sulfate (SDS) (0.007 mol · kg⁻¹ and 0.01 mol · kg⁻¹) at different temperatures. The data have been analyzed using Jones–Dole equation and the derivative parameters B and A have been interpreted in terms of ion–solvent and ion–ion interactions respectively. The change of Gibbs free energy of activation $(\mathrm{\Delta }{G}_{\eta }^{\ne })$, enthalpy of activation $(\mathrm{\Delta }{H}_{\eta }^{\ne })$, and entropy of activation $(\mathrm{\Delta }{S}_{\eta }^{\ne })$ for viscous flow of the solutions were calculated using Eyring equation, which depicts the mechanism of viscous flow. The structure making/breaking nature of the studied electrolytes has been discussed in the light of first derivative of B-coefficient (dB/dT) over temperatures. Potassium chloride and potassium nitrate acts as structure breaker in water where as all the salts are structure makers in aqueous SDS solutions, i.e. the postmicellar and pre-micellar regions.     

Thermodynamic properties of CaTiF5(s)

Calcium titanofluoride CaTiF₅(s) was prepared by solid-state reaction of CaF₂(s) with TiF₃(s) and characterized by X-ray diffraction method. The standard molar isobaric heat capacity $(C_{p\text{,m}}^{\circ })$ of CaTiF₅(s) was determined by a power compensated differential scanning calorimeter in the temperature from 230 K to 710 K. A solid-state galvanic cell with CaF₂ as electrolyte was used to determine the standard molar Gibbs energy of formation $({\mathrm{\Delta }}_{\text{f}}{G}_{\text{m}}^{\circ })$ of CaTiF₅ in the temperature range from 803 K to 1005 K. The galvanic cell can be depicted as:$(-)\text{Pt,}{\text{O}}_2(\text{g,}101.325\text{kPa})/\{\text{CaO(s)}+{\text{CaF}}_2(\text{s})\}//{\text{CaF}}_2//\{{\text{CaTiF}}_5(\text{s})+{\text{CaTiO}}_3(\text{s})\}/{\text{O}}_2(\text{g,}101.325\text{kPa})\text{,Pt}(+)$The second law analysis of present data were carried out to derive the standard entropy $S_{\text{m}}^{\circ }(298.15\text{K})$ and the enthalpy of formation ${\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{\circ }(298.15\text{K})$ and the values derived are 68.7 J · K⁻¹ · mol⁻¹ and −2848.4 kJ · mol⁻¹, respectively.     

Partial molar volumes of organic solutes in water. XX. Glycine(aq) and l-alanine(aq) at temperatures (298 to 443) K and at pressures up to 30 MPa

Density data for dilute aqueous solutions of two amino acids (glycine, l-alanine) obtained using a flow vibrating-tube densimeter are presented together with partial molar volumes at infinite dilution (standard molar volumes, $V_{\text{m,}2}^{°}$) calculated from the measured data. The experiments were performed at temperatures from (298 up to 443) K at pressures close to the saturation line of water, at pressures in the range from (15 to 17) MPa, and at 30 MPa. Values of an analogue of isothermal compressibility, ${\kappa }_{T\text{,}2}^{°}=-(1/V_{\text{m,}2}^{°})(?V_{\text{m,}2}^{°}/?p{)}_T$, are also evaluated. Maxima on the curves $V_{\text{m,}2}^{°}(T)$ and ${\kappa }_{T\text{,}2}^{°}(T)$ are observed and discussed. The new data along with literature values of standard molar volumes and heat capacities are used for generating the recommended parameterization of an equation of state for standard molar thermodynamic properties of the aqueous amino acids.     

Compressibility and volumetric studies of polyethylene-glycols in aqueous,methanolic, and benzene solutions at T = 298.15 K

The speed of sound and density measurements in water, methanol, and benzene solutions for the solutes PEG-400, PEG-1000, and PEG-4000 at T = 298.15 K (0.05 to 0.5 mol · kg⁻¹) are reported. The data obtained are used to calculate thermodynamic parameters such as adiabatic (isentropic) compressibility of solutions (β_ad), apparent molar volume (ϕ_V) and apparent molar compressibility (ϕ_K) for solute molecules in all the solvent media. The limiting partial molar volume $({\varphi }_V^{\circ })$ and limiting partial molar compressibility $({\varphi }_K^{\circ })$ of solute molecules are used to estimate volume of transfer and compressibility of transfer for PEG molecules from methanol to aqueous and benzene to aqueous media. The high observed negative $({\varphi }_K^{\circ })$ values in methanol are interpreted in terms of breakdown of one-dimensional H-bonded structure of methanolic molecules. The (${\varphi }_K^{\circ })$ values observed in water although negative but of small magnitude as compared to salts in water. Attempt is made to estimate hydration number for these molecules in aqueous solutions by applying Shiio’s method and it is observed that PEG-4000 is hydrated most. These results are discussed in terms of solute–solvent and hydrophobic interactions and effects due to conformational characteristic of high molecular weight glycol molecules.     

Hard biaxial ellipsoids revisited: Numerical results

Monte Carlo simulations are undertaken for hard ellipsoids for a number of values of its semi-axes in the range c/a∈{0.1,10}$c/a\in \{0.1\text{,}10\}$. The isotropic phase results are compared to the Vega isotropic phase equation of state for hard biaxial ellipsoids [C. Vega, Virial coefficients and equation of state of hard ellipsoids, Mol. Phys. 92 (1997) 651]. The Vega equation of state is found to perform exceedingly well for all of the models studied. The biaxial phase is seen to form only after the previous formation of a discotic phase.     

2-Pyridyloximate clusters of cobalt and nickel

The use of 2-pyridyloximate(-1) ligands, (py)C(R)NO⁻ [R = H, Ph, 2-pyridyl (py)] in cobalt and nickel(II) chemistry has been investigated and led to four families of clusters. A representative member of each family, namely $[{\mathrm{Co}}^{\text{II}}{\mathrm{Co}}_2^{\text{III}}\{(\mathrm{py})\mathrm{C}(\mathrm{ph})\text{NO}{\}}_6]({\mathrm{PF}}_6{)}_2$ (1), $[{\mathrm{Co}}_2^{\text{II}}{\mathrm{Co}}_2^{\mathrm{III}}(\mathrm{OH}{)}_2({\mathrm{O}}_2\mathrm{CMe}{)}_2\{(\mathrm{py}{)}_2\mathrm{CNO}{\}}_4(\mathrm{MeOH}{)}_2]({\mathrm{ClO}}_4{)}_2$ (2), [Ni₉(OH)₄{(py)CHNO}₁₀(H₂O)₈]{N(CN)₂}₃(ClO₄) [3{N(CN)₂}₃(ClO₄)] and [Ni₄(O₂CMe)₄{(py)C(ph)NO}₄(MeOH)₂] (4) is briefly structurally and magnetically described.