Chem. J. Chinese Universities ›› 2009, Vol. 30 ›› Issue (9): 1844.

• Articles • Previous Articles     Next Articles

Activity Coefficients of CaCl2 in Glycine+Water and Alanine+Water Mixtures at 298.15 K

ZHANG Xin-Kuan1,2, ZHUO Ke-Lei1*, MA Jing-Jing1, LIU Hong-Xun1, WANG Jian-Ji1   

  1. 1. School of Chemistry and Environmental Science, Henan Normal University, Xinxiang 453007, China;
    2. School of Chemistry and Chemical Engineering, Xinxiang University, Xinxiang 453003, China
  • Received:2008-09-01 Online:2009-09-10 Published:2009-09-10
  • Contact: ZHUO Ke-LeiE-mail: klzhuo@263.net
  • Supported by:

    国家自然科学基金(批准号: 20673033)和河南省高等学校创新人才基金(批准号: 豫高教[2002]129)资助.

Abstract:

Activity coefficients of CaCl2 in glycine+water and alanine+water mixtures at 298.15 K were determined by cell potential measurements using ion selective electodes(ISE). The molalities of CaCl2 ranged from 0.01 to 0.20 mol/kg, and those of amino acides ranged from 0.1 to 0.4 mol/kg. The cell potentials were analyzed by the Debye-Hückel extended equation and the Pitzer equation to calculate activity coefficients. The results obtained from the two theoretical models are in good agreement with each other. Standard transfer Gibbs free energy, pair interaction parameters(gEA) and salting constants(ks) were also evaluated. The results are disscussed in terms of the stereo-chemistry of amino acid molecules and structures and electrostatical interaction models. Activity coefficient of CaCl2 increases with increasing of molalities of amino acids. Standard transfer Gibbs free energy decreases with increasing molalities of amino acids, indicating that the interactions of the amino acides with CaCl2 are thermodynamically attractive in aqueous solution. Values of gEA are negative, indicating that the interactions of these two amino acides with CaCl2 result mainly from the electrostatical attraction.

Key words: Activity coefficient; Gibbs free energy; CaCl2; Glycine; Alanine

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