DETERMINATION OF AGGREGATION NUMBERS AND IONIZATION DEGREE OF MICELLES USING SURFACE-TENSION ISOTHERMS OF MALEIC-ACID MONO[2-(4-ALKYLPIPERAZINYL)ETHYL ESTERS]

By use of the slopes of surface tension isotherms at concentrations ab ove and below the critical micelle concentration, the aggregation numb ers of homogous maleic acid mono[2-4(4-alkylpiperazinyl)ethyl esters] micelles are determined at pH = 6.2, where these surfactants exist in the betain-like form. For pH values at which the adsorption of almost only one surface active ionic component of these surfactants is guaran teed, the degree of counterion binding is determined for two samples o f the homologous series. The results obtained show that the method app lied to determine these values from surface tension measurements opens a new possibility to interpret surface tension isotherms. The method needs, however, very accurate measurements because even small deviatio ns may alter the results significantly.