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  • 1
    ISSN: 1572-8927
    Keywords: Activity coefficients ; ion selective electrodes ; DL-valine ; aqueous KCl solutions ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electrochemical cells with two ion selective electrodes, a cation and an anion ion selective electrode, versus a double junction reference electrode were used to measure the activity coefficients of DL-valine at 298.15 K, up to 0.5 molality, in aqueous solutions of KCl up to 1.0 molality. The results obtained in this work are compared with those reported before for the activity coefficients of DL-valine in aqueous solutions of NaCl. The experimental data were correlated using the model proposed previously by Khoshkbarchi and Vera for the activity coefficients of amino acids in aqueous electrolytes solutions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8927
    Keywords: Activity of ions ; electrolyte solutions ; ions ; sodium nitrate ; potassium nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ion selective electrodes have been used to measure the activity coefficients at 25°C of individual ions in aqueous solutions of NaNO3 up to 3.5 molal, KNO3 up to 3.5 molal and mixtures of NaNO3 and KNO3 up to 2.4 molal total nitrate ion concentration. The experimental results confirm that the activity coefficient of anion and cation in aqueous single electrolyte solutions of NaNO3 and KNO3 were different from each other over the whole range of concentrations studied. These effects are attributed to the ion-ion and ion-solvent interactions. The results also show that the activity coefficients of nitrate ions in the presence of sodium and potassium counterions do not depend significantly on the nature of the counterions present in the solution. The experimental data obtained in this study were correlated by a model proposed previously.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 249-258 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ion-selective electrodes were used to measure the activity coefficients at 298.2 K of individual ions in aqueous solutions of NaCl and NaBr up to of 5 molal and of KCl up to 4 molal. The mean ionic activity coefficients of NaCl, NaBr, and KCl, obtained from the values of the activity coefficients of the individual ions, show good agreement with values reported in the literature. The experimental results show that the activity coefficients are different for the anion and the cation in an aqueous solution of a single electrolyte and that, as expected from the ion-ion and ion-solvent interactions, the activity coefficient of an ion depends on the nature of its counterion. A modified form of the Pitzer's model, which distinguishes between the activity coefficients of the anion and the cation, was used to correlate the experimental results.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 2354-2364 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Activity-coefficient data were measured for NaCl in the system water-NaCl-DL-valine at 25°C. The activity coefficients of DL-valine were then calculated through rigorous thermodynamic relations. The activity coefficients of the amino acids in this and other aqueous systems containing electrolytes were modeled using an expression for the excess Gibbs free energy of the solution. The model combines a contribution for long-range interactions, given either by the Bromley equation or the K-V equation, and a contribution of short-range interactions represented by a ternary NRTL or Wilson expression. The model accurately correlates the activity coefficients of ten amino acids in aqueous solutions and of six amino acids in aqueous electrolyte solutions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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