The opposite sides of the coexistence curve of a binary liquid mixture with a miscibility gap converge at the consolute point.  A mixture of isobutyric acid and water, which has a consolute point at 38.8 mass percent isobutyric acid and temperature of 26 C, serves as an example. Potassium permanganate, when added to this mixture, apparently reacts to oxidize the acid.  The rate of reaction can be followed by measuring the electrical conductivity, which diminishes exponentially with time.  The first order rate constant associated with this exponential decay was determined using the Guggenheim method.  When the rate constant measurements where plotted in Arrhenius form, the data formed a straight line for temperatures substantially above critical.  In the critical region, however, the data deviated noticeably above the straight line, indicating critical speeding up of the reaction rate [1].  Y. W. Kim, J. K. Baird, J. Phys. Chem. 2003 , 107, 8435

Crititical speeding up of the rate of reaction in a mixture of isobutyric acid + water + potassium permangante

245th National Meeting (2013)

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