DENSITY AND VISCOSITY OF OCTYL, DECYL, AND DODECYL SODIUM SULFATES INETHANOL

The-density of mixtures of a homologous series at sodium alkyl sulfate (H(CH2)(n)OSO3-Na+ surfactants (where n 8, 10, and 12) in ethanol has been measured as a function of concentration and temperature, and the apparent molal volumes have been derived. The calculated partial mola l volume of sodium ion (V degrees(Na+)) at infinite dilution from the three surfactants is found equal to -14.23, -13.75, and -10.44 cm(3.) mol(-1) at 25, 35, and 45 degrees C, respectively. The electrostrictio n of the alcohol molecules by the hydrophobic part H(CH2)(n)OSO3- has been found to be almost negligible since the central charge is partial ly masked by the large hydrocarbon group. The Jones-Dole equation is u sed to determine the ionic beta coefficient from viscosity measurement s. The data are interpreted in light of structure-making or structure- breaking phenomena.