Stability of Mixed Colloidal Dispersions
Authors: Matijevic Egon , Brace Roger , Bleier Alan 
Published: December 2007

This paper was prepared for the Oilfield Chemistry Symposium of the Society of Petroleum Engineers of AIME, to be held in Denver, Colo., May 24–25, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
The stability of colloidal dispersions consisting of a mixture of particles differing in chemical composition, particles differing in chemical composition, size, shape, and charge has been studied. The investigated systems were prepared from (a) two different preformed sols, (b) one preformed sol and the other precipitated in situ, and (c) two sols precipitated in situ, and (c) two sols simultaneously precipitated from homogeneous electrolyte solutions. The colloidal materials used in this work were polyvinyl chloride (PVC) latex, silica, polyvinyl chloride (PVC) latex, silica, and aluminum hydroxide, in various combinations. The properties of the mixed sols were followed as a function of pH and of electrolyte content by means of light scattering and electrokinetic measurements. The data were presented in terms of the precipitation/stability domains which delineate conditions resulting in dispersions of various degrees of stability. In precipitating systems attention was drawn to the solubilities of the individual sparingly soluble materials.

Introduction
Stability of colloidal dispersions depends on the properties of the suspended particles (their size, shape, charge, particles (their size, shape, charge, type of stabilizing ions, and degree of solvation) and on the nature and the concentrations of the solutes in the suspending medium. Specifically, the complexing among various solute species and the interactions of the solutes or their complexes with the stabilizing or constituent ions of the dispersed articles have a profound effect upon the sol properties. Systematic studies carried out over the last decade or so have led to an elucidation of a great many phenomena in colloid stability, particularly as related to solid/solute particularly as related to solid/solute interactions. The vast majority of the investigated systems consisted of one kind of dispersed particles. In particular, major effort was made to particular, major effort was made to produce such particles as uniform in produce such particles as uniform in size and shape as possible in order to simplify the model systems and to facilitate theoretical interpretations.
In nature and in various applications, the colloidal dispersions usually consist of a mixture of particles which may differ greatly in chemical composition, size, shape, degree of solvation, and charge.