Density of polystyrene and polyvinyltoluene latex particles

Abstract

The accurate determination of particle diameters from light scattering by means of functions derived from the Mie theory requires that the density of the particles be known very accurately since it enters the evaluation of both refractometric and scattering data. For this reason the densities of a series of monodisperse polystyrene and polyvinyltoluene latices were determined by using differential pycnometry introducing a few new features into this technique. It is shown that the technique, as used, should be capable of giving, with suitable systems, seven significant figures for the particle density. Such a high accuracy could not be aimed for in the three-component system used nor was it needed, the actual uncertainty occurring in the fifth figure. The data, apart from satisfying the purpose stated, showed that the density varies only a little with the particle diameter within the colloidal range.