Theory, Production and Mechanism of Formation of Monodispersed Hydrosols

Abstract

1. Monodispersed colloids exhibiting higher order Tyndall spectra have been prepared by precipitation of sulfur from ethanol and acetone solutions by the careful addition of water. 2. The relationship between the concentration of sulfur and the volume fraction of water at the critical point of sulfur-ethanol-water solutions has been investigated. 3. Sols prepared by this dilution method have been investigated as to dispersion of wave length in their angular scattering of visible light and their transmission as a function of wave length. 4. The size, number and charge of the particles of such sols are in the same range as those prepared by the acid decomposition of sodium thiosulfate. 5. The rates of growth of sols prepared by such a dilution method have been investigated. The growth rates obtained have been reproduced from previous theoretical considerations which allow the estimation of the value of the diffusion coefficient of S8 in alcohol-water and acetone-water mixtures. The value of this diffusion coefficient lies in the range 7-8 × 10−6 cm.2/sec. for both media. The application of this method for estimating diffusion coefficients is valid for any colloidal system that is characterized by a small particle size distribution at all stages of its growth. 6. A qualitative explanation is offered for the necessary conditions under which monodispersed colloids may be prepared for both the dilution and acid decomposition of sodium thiosulfate methods. © 1950, American Chemical Society. All rights reserved.