Collect. Czech. Chem. Commun. 1994, 59, 99-105

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

Mária Vojteková, František Kopecký, Olga Greksáková and Jarmila Oremusová

Department of Physical Chemistry, Faculty of Pharmacy, Comenius University, 832 32 Bratislava, Slovak Republic


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.