A simple method for determination of surface volume mean diameters of oil in water submicron emulsions.

Plots of the droplet size parameter, alpha = (pi(n)D / lambda) versus the total scattering coefficient or specific turbidity, K, are sinusoidal curves. It was noticed that, along one branch of the K-alpha curve (up to 1.1 microm for relative refractive indices (rr(I)) < 1.2), the wavelength dependence on turbidity; i.e. the extent to which light at different wavelengths is scattered showed a progressive decrease with increase in droplet diameter. It was in fact found that when the logarithm of the relative standard deviations (RSD's) in specific turbidities at four different wavelengths (for a particular droplet diameter and relative refractive index) was plotted as a function of that diameter, a straight line resulted. This relationship provides a valuable new method for estimating the surface volume mean droplet size, D(vs), for submicron emulsions by means of simple spectro-turbidimetry.