Author: Mukhopadhyay L. Mitra N. Bhattacharya P.K. Moulik S.P.
Publisher: Academic Press
ISSN: 0021-9797
Source: Journal of Colloid and Interface Science, Vol.186, Iss.1, 1997-02, pp. : 1-8
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Abstract
The ternary phase diagrams for the formation of biological microemulsions of the combinations CA/AOT/water and CA/Tween 20/water have been presented. The thermodynamics of solution of water in AOT/CA as well as in Tween 20/CA forming w/o microemulsions and solution of oil in Tween 20/water forming o/w microemulsions have been calorimetrically studied. The solution processes are essentially exothermic (with a few exceptions) and have yielded negative entropies, i.e., producing an ordering effect. This has been supported by the measured specific heats of the resulting solution. The pseudo-first-order rate constants ( k 1 ) for the alkaline fading of crystal violet in w/o microemulsion medium for the CA/AOT/water and CA/TW 20/water have been found to depend on [water]/[AOT] mole ratio (omega) with maxima at omega = 10. For o/w preparations of CA/TW-20/water, k 1 has shown maximum at [CA]/[TW-20] mole ratio omega' = 2, whereas the k 2 value has increased with omega'. The salt effect on the reaction has shown significant deviation from expectation in w/o microemulsion. The free energies of activation for the w/o and o/w systems are of the same order, whereas both Delta H ++ and Delta S ++ values differ significantly.
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