Abstract: Aggregation numbers of micelle (Nm) of SDS and AS were determined by steadystate fluorescence probe method in which pyrene was used as fluorescence probe and benzophenone as quencher.Satisfactory results were obtained as shown in Fig.1～2 when the solution of surfactant was prepared with a saturated aqueous solution of pyrene and the optimum concentration of benzophenone was selected in 0～1.00 mmol L－1.The experimental results in Fig.3～5 and Table 4 show that when concentration of surfactant is in 5～9 times of cmc,Nm increases linearly with the increase of concentration and fluctuats slightly with the increment of temperature.It is indicated that Nm is an eigenvalue at c=cmc,which has been defined herefrom as the critical micellar aggregation number [Nm].[Nm] can be extrapolated from Nm～cSAA experimental curves,as shown in Table 3 for SDS 57 (25℃) and 49 (40℃) and for AS 55 (40℃) ,respectively.

Key words: Critical micellar aggregation number, Fluorescence probe, Aggregation number of micelle, Sodium dodecyl sulfate(SDS), Sodium dodecyl sulfonate(AS)