Acta Phys. -Chim. Sin. ›› 1993, Vol. 9 ›› Issue (05): 668-674.doi: 10.3866/PKU.WHXB19930518

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Thermodynamics of the Dissociation of Weak Electrolyte in Mixed Solvents(I)

Zhang Zi-Fu; Yang Jia-Zhen; Yang Qi-Zhi; Yang Yong-Zhen; Liu Wei; Li Hui   

  1. Department of Chemistry Liaoning University, Shenyang 110036
  • Received:1992-02-21 Revised:1992-07-24 Published:1993-10-15
  • Contact: Yang Jia-Zhen


The dissociation degrees of bromophenol blue at various total ionic strengths in pure water and in 15%, 25 mass% ethanol-water mixed solvents were measured by U-3200 spectrophotometer, and the pH values of corresponding solution were also measured by Orion EA 940 ionometer. The thermodynamic dissociation constants of bromophenol blue in pure water and in the mixed solvents were determined by two methods: extrapolation and polynomial approximation. The effect of medium on absorption spectra of bromophenol blue was discussed.

Key words: Absorption spectra; Isosbestic point; Dissociation constant; Pitzers equation; Indicator; Bromophenal blue