Composition of sodium taurocholate micellar solutions

The composition and range of existence of aggregates formed by sodium tauro cholate in aqueous micellar solutions were studied. Electromotive force mea surements were used to obtain concentrations of free hydrogen and sodium io ns. Experimental data obtained at 25 degrees C and at three N(CH3)(4)Cl con centrations, used as anionic medium, can be explained by assuming the prese nce of aggregates with different compositions depending on the reagent conc entrations and the ionic strength. Comparison with taurodeoxycholate shows wide differences. Protonated species of taurocholate are observed only at p H less than or similar to 5. At higher pH, the micellar aggregate distribut ion remains nearly constant at a given ionic medium concentration. As expec ted, the size of the micellar aggregates increases on increasing the ionic strength. A dimer is found at all concentrations of the ionic medium. All s pecies found have aggregation numbers of anions in multiples of two. The af finity of sodium ions for micellar aggregates is greater than that of N(CH3 )(4)(+) ions.