• Vishnu

      Articles written in Proceedings – Section A

    • Transition phenomena at saturation temperature

      Vishnu

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    • Studies on the kinetics of the decomposition of murexide in acid solutions

      N A Ramaiah S L Gupta Vishnu

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      Decomposition of murexide in solutions of low pH (2–6) has been investigated spectrophotometrically. At pH<6, the characteristic absorption of of murexide at λ=530 mμ decreased irreversibly with time, following first order law; the corresponding rate constantk1 had a value of 7·98×10−6 min.−1 (25° C.) for an initial concentration of 0·125 mM of murexide at pH=2·2.

    • Polarographic studies of murexide—I

      N A Ramaiah Vishnu

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      Reduction of murexide at the dropping mercury electrode was investigated. Data obtained at different concentrations in the range 0·5-2 mM showed that the half-wave potential of murexide was −0·38 voltvs. S.C.E. in 0·1 N KCl solution (neutral pH) and was not altered with concentration; with this last, the diffusion current increased linearly. Analysis of the plots log (i/id−i) vs. E indicated that the reduction was irreversible in nature.

    • Studies on the kinetics of the salt effects on the decomposition of murexide in acid solutions

      N A Ramaiah S L Gupta Vishnu

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      The decomposition of murexide in acidic solutions was studied spectro-photometrically employing different strong acids like HC1, HBr and HNO3 and mixtures of these acids and neutral salts like KCl, KBr, KI and KNO3. The velocity constant k appeared to be a linear function of the concentration C of the strong acid used, and obeyed a relationship:k/min-1=2.56×10-3C The slope of the line was unaffected by the change in the nature of the acid or added salt indicating that the anions had no effect on the velocity constant.

    • A new spectrophotometric method for the determination of copper with sodium versenate

      N A Ramaiah Vishnu

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      Employing the absorption at λ=630 mμ of copper ammonium complex, a new method for determination of Cu++ by sodium versenate was described. The experimental error involved in the method was less than 1%.

    • A polarographic study of mercuric cyanide complexes with alkali halides

      A K Agrawal Vishnu R C Mehrotra

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      A polarographic study of the complexation reactions between mercuric cyanide and alkali halides has been carried out. In basic solutions, the existence of two species Hg (CN)2 X and Hg (CN)3 X−= being reduced has been concluded (where X=Cl, Br or CNS). The cyanide released by the reduction combines with Hg (CN)2 X at or around the surface of the drop to form Hg (CN)3 X−=. The logarithms of the overall formation constants of these species at an ionic strength of 2·0 are: 36·19 and 39·43 for chloride, 35·99 and 39·10 for bromide and 36·30 and 38·74 for thiocyanate complexes.

    • Transition phenomena at saturation temperature studies on electrolytic conductance of alkali halides in aqueous systems

      Vishnu Awadhesh K Singh

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      A plot of negative logarithm of the electrical conductance (K)vs reciprocal of the absolute temperature (T) shows the existence of the transition in the systems ‘Electrolyte-Sucrose-water’, ‘Electrolyte-Mannitol-water’, and ‘Electrolyte-Xylose-water’. A saturated solution of sucrose/mannitol/xylose containing a known amount of an electrolyte was prepared at a temperature of 50·0±0·05° C and the crystals were separated by centrifugation at the same temperature. The conductance of the centrifugate was measured in a tubular conductivity cell at different temperatures in the range between 30° C to 70° C. The plot of −log10 Kvs 1/T showed a break at the saturation temperature, the point where two straight lines appeared to intersect. The transition can be explained on the basis of change in the water structure due to the presence of ‘structure-breaking’ and/or ‘structure-making’ ions. These sucrose, xylose, and mannitol molecules due to the presence of a number of hydrogen bonding sites contribute largely toward the build up of big structures in the supersaturated state. These structures crumble as the system undergoes the transition at the saturation temperature. Different electrolytes produced more or less similar effect.

    • Transition phenomena at saturation temperature conductance study of alkali halides in formamide in the presence of nonelectrolytes

      Vishnu Awadhesh K Singh

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      The interaction between alkali halide ions and organic nonelectrolytes in formamide solutions was followed by conductance measurements. A saturated solution of the nonelectrolyte (sucrose and mannitol) containing a known amount of the alkali halide salt was prepared at 50.0 ±0.05° C. Crystals were separated by contrifugation at the same temperature. Conductance of the centrifugate was measured at different temperatures between 30° and 70° C. Plots of — logk vs. 1/T showed a break at the saturation temperature where two straight lines appeared to intersect. This transitional behaviour has been explained on the basis of (i) the change in solvent structure, (ii) hydrogen bonding, and (iii) ion solvation.

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