Effect of Addition of KX Type Electrolytes and Temperature on the Critical Micellar Concentrations of 1-Cetylpyridinium and Carbethopendecinium Bromides

Abstract

The critical micellar concentrations (cmc) of the title cationic surfactants were measured in aqueous solutions at 25 °C in the presence of KBr, KF, KCl, KI, KSCN, KNO3, KAc and HCOOK. The conductometric and, in part, potentiometric methods employing ion selective electrodes were used. For 1-cetylpyridinium bromide in the absence of any of the electrolytes, the decreasing temperature dependence of cmc was measured conductometrically over the region of 12 - 40 °C and the association degree of the micelles with Br- anions was calculated. The decrease in cmc of the two surfactants due to the presence of electrolytes (in concentrations up to tenfold cmc) was expressed by means of a semiempirical equation. There are indications that I- and SCN- anions enter into specific interactions with micelles.