The relation for the free energy of micellization in case of ionic a well a nonionic safectants has been updated by including the effect of ionic strength and the size of the ions used. For the verification of the final relation and to compare the results one gets through differed techniques like viscometry, light absorption\transmission, surface tension and conductance have been employed to determine critical micelles concentration (CMC) of sodium dodeoyl sulphate and sodium tetradeoyl adphde safactanta It is found that when the electrolyte concentration is very low the viscometry does not give reliable results where a light absorption/transmission does. The surface tension measurement and conductance measurement give reliable and reproducible results at any electrolyte concentration and temperature. A new way of interpretation of conductivity data has also been proposed, through which one can get better remits even in the presence of high ionic strength. The results no obtained show the decrease in CMC with the increase in electrolytes concentration andapproaches to a constant value. This decrease is in the order of Na+>K+> Li+ . This trend isexplained in terms of change in shape of the micelles, specific absorption of electrolytes, variation in double layer thickness and hence variation in the free energy of the system and hydrodynamic radius of the ions used. It is also found that the CMC decreases with the increase in temperature of the system, which is explained in terms of solubility of thesurfactants, change in shape of the micelles and free energy of the system with the temperature. Further these variation are in accordance with the equation derived by us.
G HAMEED ,A BANO ,M K BALOCH ,
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