Abstract
The effect of ethanol on the aqueous solution in which limonene was solubilized by nonionic surfactants, polyoxyethylene polyoxypropylene 2-decyltetradecylethers (PEN) and polxyethylene hydrogenated castor oil (HCO), has been studied. The oxyethylene chain length of these surfactants to achieve maximum solubilization at room temperature was affected by adding ethnol. The optimum oxyethylene chain length shifted to shorter chain length with increasing concentration of ethanol. The minimum amount of these suractants to give transparent solutions containing limonene in the range of 0 to 40°C was determined in the respective aqueous solutions. The P/S ratios were calculated from the amount of limonene (P) and the minimum amount of these surfactants (S). We have termed it the limited P/S ratios. The solubillizing power in aqueous solutions of these surfactants was evaluated from the limited P/S ratios. The limited P/S ratios in the case of PEN series increased with increasing concentration of ethanol, but in the case of HCO series those decreased until 2%, and then increased.
