Toluene/water/1-propanol interfacial tension measurements by means of pendant drop, spinning drop, and laser light-scattering methods

Abstract

Measurements of low interfacial tension, γ i, ranging from 0.3 to 3 mN/m (dyn/cm), on water/toluene interfaces containing various amount of 1-propanol have been undertaken with laser light-scattering, spinning drop, and pendant drop methods. A Lorentzian-squared function has been found to represent the instrument contribution to the spectrum obtained from the laser light-scattering method. The interfacial viscosity was calculated from the spectral linewidth using this instrumental function and compared to the bulk viscosity. Phase volume and interfacial tension measurements indicate that a requirement for formation of O W dispersion is low γ i, but for overall stability, γ i, although small, must be positive. From extrapolation of the measured γ i values, it has been found that a residual positive value of 0.2 mN/m is still observed at cosolubilization.