Journal of Surfactants and Detergents

, Volume 17, Issue 3, pp 525–530 | Cite as

Effect of Electrolytes on the Krafft Temperature of Cetylpyridinium Chloride in Aqueous Solution

  • Md. Nazrul Islam
  • Khokan Chandra Sarker
  • Gazi Aktaruzzaman
Original Article


This paper presents the effect of some electrolytes on the Krafft temperature (T K) of cetylpyridinium chloride in aqueous solution. The results show that more chaotropic anions raise while less chaotropic anions lower the T K of the surfactant. More chaotropic Br, SCN and I form contact ion pairs with the cetylpyridinium ion and reduce the electrostatic repulsion between the surfactant molecules. As a result, these ions exhibit salting-out behavior, showing an increase in the T K of the surfactant. On the other hand, less chaotropic NO3 increase the solubility of the surfactant, with a consequent decrease in the T K. Surface tension data of the salt solutions reveal that more chaotropic ions show a relatively less molar increase in surface tension compared to less chaotropic ions. This indicates that less chaotropic ions have a preferential tendency to be negatively adsorbed at the air–water interface as well as hydrocarbon–water interface and thereby disturb the hydration of the surfactant. SO4 2− being a strong kosmotrope cannot form contact ion pairs with the cationic part of the surfactant. Rather this ion preferentially remains in the bulk because of its strong tendency for hydration and thereby stays apart. As a result, SO4 2− also causes a significant lowering of the T K of the surfactant. Thus it appears that contrary to the usual trend SO4 2− behave like a chaotrope showing salting-in effect of the surfactant.


Krafft temperature Hofmeister effect Kosmotropes Chaotropes Cationic surfactant 



Authors thank the members of the Board of Postgraduate Studies for helpful discussion during the preparation of the research proposal. The financial assistance (CASR-236/32) approved by the Committee for Advanced Studies and Research (CASR), BUET for carrying out the present work is highly appreciated.

Supplementary material

11743_2014_1577_MOESM1_ESM.doc (234 kb)
Supplementary material 1 (DOC 233 kb)


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Copyright information

© AOCS 2014

Authors and Affiliations

  • Md. Nazrul Islam
    • 1
  • Khokan Chandra Sarker
    • 1
  • Gazi Aktaruzzaman
    • 1
  1. 1.Department of ChemistryBangladesh University of Engineering and TechnologyDhakaBangladesh

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