APPLICABILITY OF THE LEVICH EQUATION FOR A 2-PHASE SOLUTION IN THE ROTATING-DISK ELECTRODE SYSTEM

The mass‐transter characteristics of a two‐phase system formed by mixing a fixed quantity (20 v/v%) of organic solvent with an aqueous ferricyanide electrolyte solution in an RDE system were studied. The Levich eqution, I1 = 0.62 nFACbD2/3v−1/6ω1/2, was found to be applicable to the two‐phase system with only a minor modification in the angular velocity (ω) at Reynolds numbers between 3–5 × 104. The experimental results indicate that the interfacial tension is the most important variable for the two‐phase system. One group of organic solvents with smaller interfacial tension, such as benzene or toluene, needs a modification of the Levich equation by replacing the observed angular velocity (ωo) with the true angular velocity (ωt) which was observed to be 1.1 times the observed angular velocity. For the other group with larger interfacial tension, such as n‐hexane or cyclohexane, there is no need to modify the observed angular velocity. In other words, the Levich equation may be expressed as I1 = 0.65 nFACbD2/3v−1/6ω1/2 for two‐phase solution if the interfacial tension is smaller than 37.0 dyne/cm. Copyright © 1990 The Chemical Society Located in Taipei & Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim, Germany