Pseudo-first-order rate constants (k obs ) for pH-independent hydrolysis of phthalimide (1), obtained at a constant total concentration of cetyltrimethylammonium bromide and hydroxide ([CTABr] T ), 2.0×10 −4 M 1, 0.02 M MOH (M + = Li + , Na + and K + ) and various concentrations of inert salt MX (= LiCl, LiBr, NaCl, NaBr, KCl and KBr), follow a relationship derived from the pseudophase micellar (PM) model coupled with an empirical equation. This relationship gives empirical constants, F X/S and K X/S , with S representing anionic 1. The magnitude of F X/S is the measure of the fraction of micellized anionic 1 (S − M ) transferred to the aqueous phase by the limiting concentration of X − . The value of K X/S is the measure of the ability of the counterions (X − ) to expel the reactive counterions (S − ) from the cationic micellar surface to the aqueous phase. The values of F X/S are ∼ 1 for MBr (M + = Li + , Na + and K + ) and in the range ≤ 0.7 to ≥ 0.5 for MCl (M + = Na + and K + ) at 0.006, 0.010 and 0.016 M CTABr. For