NOPR Collection:

Acid-base catalyzed photoinduced redox reactions of phenosafranin- EDTA system in photoelectrochemical cell

2019-03-26T06:44:34Z

Title: Acid-base catalyzed photoinduced redox reactions of phenosafranin- EDTA system in photoelectrochemical cell Authors: Jana, Asok K; Bhowmik, Benoy B Abstract: The photogalvanic effect in phenosafranin-EDTA aqueous system has been studied at different pH. The photovoltage growth and decay curves follow the functional forms related to the relaxation times. Under the experimental conditions, the inverse of relaxation time or the rate of electrode reaction is pH-dependent. The rate constants (k) of forward and backward reactions at 25°C have been calculated. From the plot of log k versus pH, catalytic constants for H⁺ and OH^- have been determined. The calculated free energy of electron transfer across the electrode/ electrolyte interface is about - 5.66 kJ mol^-1. Page(s): 351-355

Equilibrium studies for the sorption of metal ions onto Chitosan

2019-03-26T06:43:17Z

Title: Equilibrium studies for the sorption of metal ions onto Chitosan Authors: McKay, Gordon; Blair, Henry S.; Findon, (Miss) Anne Abstract: The sorption of four metal ioss, viz. Hg(II), Cu(II), Ni(II) and Zn(II) onto chitosan has been studied. The monolayer sorption capacity is 815, 222, 164 and 75 mg g^-1 chitosan for mercury, copper, zinc and nickel ions respectively, at 25°C and at a particle size in the range of 710-1000 μm, The effect of chitosan particle size and solution temperature on the sorption capacity has been investigated. The equilibrium isotherms have been analysed using the Langmuir isotherm model. Page(s): 356-360

A study of alkali metal ion hydration by polarographic half-wave potential shifts

2019-03-26T06:41:57Z

Title: A study of alkali metal ion hydration by polarographic half-wave potential shifts Authors: lzonfuo, Welford-Abbey Lolo; Malinowski, Edmund R Abstract: Differential pulse polarograms of 0.001M solution of alkali ions are obtained with specially prepared, bridged, saturated calomel electrode. The differential pulse peaks are corrected for pulse amplitude and bridge potentials. The half-wave potentials are measured over the complete range from pure water to pure dimethylformamide (DMF). Shifts in polarographic half-wave potentials of the alkali ions in water-(DMF) mixtures are interpreted to be, primarily, the result of direct binding between the solvent molecules and the cations, forming solvent cationic complexes that exist in dynamic equilibrium with the precursors. Equations are derived to show that the half-wave potential shift of a cation in the mixed solvent system is related not only to the concentrations ot the component solvents but also to the solvation numbers, as well as the complex formation constants. Using the derived equations, the hydration numbers of Na⁺, K⁺, Rb⁺, and Cs⁺ are determined to be 4.0 ± 0.2, 3.4 ± 1.3, 4.3 ± 1.3 and 3.9 ± 1.3 respectively. The pKa values for the formation of the hydrated species of these ions are found to be - 4.9 ± 0.1, -4.7 ± 0.1, - 4.3 ± 0.1 and - 3.4 ± 0.2 respectively. Page(s): 361-365

Thermodynamics of transfer of amino acids from water to ethanol-water mixtures

2019-03-26T06:40:49Z

Title: Thermodynamics of transfer of amino acids from water to ethanol-water mixtures Authors: Jahagirdar, D V; Arbad, B R; Chondhekar, T K; Pankanti, (Miss) S U Abstract: Dissociation constants of -tryptophan, -histidine, -aspartic acid, -glutamic acid and t-serine have been determined in water and ethanol-water mixtures at 298 K potentiometrically by the Calvin-Bjerrum titration technique. These values have been used to calculate the free energies of transfer G(i) involved in the dissociation equilibria. G (RH) and G(R^2-) have been calculated (RH^±) being the zwitter ion) knowing the solubilities of these acids in ethanol-water mixtures. Contribution due to amino acid side chain to the free energy of transfer from 100% ethanol to water has been estimated in acidic, neutral and basic media. The equivalence of these values confirms the hydrophobicity scale first proposed by Nozaki and Tanford [J bioi Chem, 246 (1971) 2211]. Page(s): 366-370