NOPR Collection:

Jug handle bifurcation and complex oscillations in reactive systems

1990-10-01T00:00:00Z

Title: Jug handle bifurcation and complex oscillations in reactive systems Authors: Rastogi, R P; Misra, G P Abstract: Bifurcation features and deformation of limit cycles for NaH₂PO₂ + cyclohexanone/acetone + Mn²⁺ + BrO₃^- + H₂SO₄ oscillatory reaction systems have been reported. Acetone system yields unperturbed limit cycles whereas in the case of cyclohexanone system, the limit cycles are deformed and knot is obtained. It is found that quasi periodicity and appearance of loop are not necessarily related. Computer analysis shows that deformation of limit cycle can occur when there is a phase difference or new harmonics appear in the time series. Page(s): 941-944

Deprotonation and transfer energetics of diglycine and triglycine in aqueous mixtures of urea and glycerol from emf measurements at different temperatures

1990-10-01T00:00:00Z

Title: Deprotonation and transfer energetics of diglycine and triglycine in aqueous mixtures of urea and glycerol from emf measurements at different temperatures Authors: Talukdar, Himansu; Rudra, Sibaprasad; Kundu, Kiron K Abstract: The two-stage deprotonation constants of diglycine and triglycine have been determined from emf measurements of cells without liquid junction comprising H₂/Pt and Ag-AgCl electrodes at five equidistant temperatures in the temperature range of 15°to 35°C in aqueous mixtures of urea and glycerol and also in water in the case of triglycine. Medium effect on deprotonation of the acids, i.e. δ (X) (X = G or S) has been dissected into transfer free energies (G and entropies (H) of the species involved using the pre-evaluated values of the zwitterions (RH^±) and of H⁺ based on the widely used tetraphenylarsonium tetraphenylborate (TATB)reference electrolyte assumption. Attempts have been made to discuss the free energy and entropic contributions of the different species involved in the protolytic equilibria in terms of the their solvation behaviour as guided by the acid-base, dispersion and electronic characteristics of the acid-base species and of the cosolvent molecules and of their aqueous mixtures, besides the superimposed cavity and Born-type electrostatic effects. Page(s): 945-952

Solubilities and thermodynamics of transfer of o- and m-substituted benzoic acids in aqueous binary mixtures of 2-methoxyethanol and 1,2-dimethoxyethane

1990-10-01T00:00:00Z

Title: Solubilities and thermodynamics of transfer of o- and m-substituted benzoic acids in aqueous binary mixtures of 2-methoxyethanol and 1,2-dimethoxyethane Authors: Ghosh, S K; Hazra, D K Abstract: The solubilities of o- and m-substituted benzoic acids in 2-methoxyethanol (ME) + water and 1,2- dimethoxyethane (DME) + water mixtures (0-100%) have been measured at 25 ±0.01°C. The thermodynamic dissociation constants of the acids have been determined from pH and solubility measurements. The free energies of transfer of the substituted benzoate ions [DG (A^‑)] from water to mixed solvent systems have been evaluated from the corresponding DG values of the acids and DG(H⁺) values previously determined in these solvent systems. The results have been interpreted in terms of the structural changes occurring in the solvent mixtures with the change in solvent composition. Page(s): 953-957

Partial molar volumes and viscosities of some multicharged electrolytes in dimethyl sulphoxide-water mixtures

1990-10-01T00:00:00Z

Title: Partial molar volumes and viscosities of some multicharged electrolytes in dimethyl sulphoxide-water mixtures Authors: Parmar, ML; Rao, Ch V Nageshwara Abstract: Partial molar volumes and viscosities of ammonium aluminium sulphate and potassium aluminium sulphate have been determined in dimethyl sulphoxide (DMSO) + water (5, 10, 15 and 20 wt %) mixtures at different concentrations and temperatures. The density data have been analysed using Masson's equation. The limiting apparent molar volumes (ϕ) and the slopes (S) have been interpreted in terms of solute-solvent and solute-solute interactions, respectively. The ϕ values vary with temperature as a power series of temperature. Structure making/breaking capacities of the multi-charged electrolytes have been inferred from the sign of (∂²ϕ/∂ T²). Both multi-charged electrolytes behave like the symmetrical tetraalkylammonium salts and act as structure makers/promotors. The experimental results of viscosity have been analysed using the Jones-Dole equation. The activation parameters of viscous flow have been obtained to throw light on the mechanism of viscous flow. Page(s): 958-962