邻苯二甲酸在异丙醇-水混合溶剂中电离热力学性质的研究

STUDY ON THERMODYNAMICS OF THE DISSOCIATION OF o-PHTHALIC ACID IN ISOPROPANOL-WATER SOLVENT MIXTURES

有机酸在混合溶剂中电离热力学性质的研究,无论在化学还是在生物领域中都有十分重要的意义。长期以来,人们对其进行了大量的研究,但对芳香族酸在混合溶液中的电离热力学性质的研究还只限于单取代苯甲酸在乙醇-水等少数几种混合溶剂中的热力学性质。为此,我们在278.15—318.15K范围内测定了无液接电池:

The first thermodynamic dissociation constants of o-phthalic acid were determined at five temperatures from 278.15 to 318.15K 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 Dehye-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_2T. The thermodynamic quantities of dissociation in the mixed solvents have been calculated, and the results have been discussed.