Small-angle X-ray scattering determination of the electron density of the particles in a colloidal suspension

Two different small-angle X-ray scattering methods have been used to determine the electron density of the particles in a colloidal silica suspension. In the first method, the electron density of the particles was calculated from the measured change of the zero-angle scattered intensity caused by the addition of known quantities of sucrose to increase the solvent electron density. In the second method, the scattering from the suspension was compared with the scattering from a nearly ideal gas. Within an experimental uncertainty of about 5%, the electron density of the silica particles was found by both methods to have a value corresponding to pure SiO₂ particles with the mass density 2.28 g.cm^-3 which is listed in the manufacturer's literature describing the suspensions. This determination of the electron density will enable these suspensions to be used as standard samples in determinations of the ratio of the scattered intensity to the incident intensity.