Acta Phys. -Chim. Sin. ›› 1991, Vol. 7 ›› Issue (05): 627-631.doi: 10.3866/PKU.WHXB19910523

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Study on Thermodynamics of the Dissociation of o-Phthalic Acid in Isopropanol-Water Solvent Mixtures

Jiang Xiang-Shun; Liang Chun-Yu; Qin Mei-Jie   

  1. Department of Chemistry, Liaoning University, Shenyang 110036
  • Received:1990-05-16 Revised:1990-12-30 Published:1991-10-15
  • Contact: Jiang Xiang-Shun

Abstract: The first thermodynamic dissociation constants of o-phthalic acid were determined at five temperatures from 278.15 to 318.15 K in 10, 14.93 and 20 wt% isopropanol-water solvent mixtures, by precise e. m. f. measurements of hydrogen-silver chlorld electrodes in cells without liquid junction. On the basis of Pitzer's theory, the method of polynomial approximation was used to determine the dissociation constants of H_2P and the results obtained were compared with traditional extrapolation according to the extended Debye-Huckel equation Results obtained from both methods agree within experimental error. The dependence of the first thermodynamic dissociation constant on temperature was given as a function of the thermodynamic temperature T by the empirical equation: pK_1=A_0+A_1/T+A_2/T. The thermodynamic quantities of dissociation in the mixed solvents have been calculated, and the results have been discussed.

Key words: o-Phthalic acid, Isopropanol, Dissociation Constant, Thermodynamics