In the present study densities of SDS + water, SDS + water + propanol and SDS + water + fructose, DTAB+ water, DTAB+ water + propanol and DTAB +water +fructose have been measured at different concentrations and temperatures. From density measurements, apparent molar volumes have been calculated for the studied systems to study the effect of added co-solute/ co-solvent on the structure of the studied systems. The observed apparent molar volumes in SDS/ DTAB + water + propanol ) systems are found to be less than in SDS/ DTAB + water system. This is due to entrapping of SDS/ DTAB molecules within the cavities of water-propanol complex1.The decrease in apparent molar volumes of SDS/DTAB in water-propanol system are more significant due to deeper penetration of propanol in interior of miclle in comparison to fructose. The apparent molar volume of SDS / DTAB + water + fructose system do not change appreciably with increasing concentration of surfactant, because of poor micelleadditive interactions( only weak hydrophobic interactions in water). Water structure breaks at higher temperatures, owing to that with increase of temperature φv (apparent molar volume) values increase in all the studied systems.
