Viscometric Study of the Effects of Added Electrolytes on the Critical Micelle Concentration of Triton X-100 in Aqueous Medium

G.O. Ogunlusi, T. O. Bakare, A. J. Akodu, I. A. Busari


Viscometric study of the effect of five electrolyte additives (HCl, HClO4, HNO3, Na2SO4 and NaCl) on the critical micelle concentration of a nonionic surfactant, Triton X-100, was investigated at 30 0C using U-type Ostwald viscometer. Density measurements of Triton X-100 solutions in the presence of varying electrolyte concentrations were carried out using pycnometer. The electrolytes were studied in the concentration range 0 – 0.1 mol dm-3. All the electrolytes were observed to lower the critical micelle concentration (CMC) of TritonX-100 significantly in the concentration range studied with HCl having the highest CMC decreasing effect up to a factor of over 400. The results have been explained based on salting-out effect. The observed trend of the CMC lowering effect of the acids: HClO4 < HNO3 < HCl followed the Hofmeister series while greater CMC reducing effect of Na2SO4 than that of NaCl can be attributed to ionic strength effect. 

Key words: additives, critical micelle concentration, electrolyte, salting-out, viscosity

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