Binding of sodium ion to alkylsulfate micelles in the presence of electrolytes: Electromotive force measurements

Counterion Effects in Aqueous Solutions of Cationic Surfactants: Electromotive Force Measurements and Thermodynamic Model

“…Such a plot ( Fig. 2) presents two different linear parts that are already described in the literature (16). For concentration below the CMC, the surfactant salt behaves like a strong electrolyte and the response of the electrode is nernstian (the slope of the EMF versus the logarithm of the total amount of surfactant varies between 57 and 60 mV per decade).…”

“…It is also to be underlined that relations [17] do not bring new information because they come from the same origin as equation [16]. Second case: solubility equilibrium of a salt AX.…”

“…In a more simple case where z X ϭ Ϫz A , the previous expressions [10], [15], and [16] become more simplistic. Relation [10] leads to…”

Contribution of micelles to ionic strength of surfactant solution

“…Assuming that the Debye-Hückel theory can be applied to calculate the y Mic value, and that a i has the same value for all species [2], Eq. (12) can be rewritten as (14) ln…”

“…The main difference between the two models is the concentration dependence of monomer activity (a x ) at surfactant concentrations (c t ) higher than the critical micelle concentration (cmc): according to PSM, a x should stay constant for c t > cmc, while MAM, as proved by potentiometric measurements [12][13][14][15][16][17][18][19][20], predicts an increase of a x even above cmc until it reaches maximum (at c t not much higher than cmc) and then it starts to decrease. Concentration dependence of species activities in the surfactant solution is of great importance, since by knowing it one can calculate concentrations of species required for determination of the aggregation number (N ) and the counterion binding parameter (α).…”