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-double dagger and Delta S-double dagger values differ significantly.