INTRODUCTION

A colloid is a suspension in which the particle size of the dispersed medium is so small (1-1000nm) that gravitational forces are negligible and the interactions are dominated by short-range forces such as van der Waals attractions and local surface charges.[1,2] The most distinguishable thing is that the contact area between the suspended particle and liquid is so large that the interparticle forces between particles are a dominant effect. The interparticle forces are classified as either attractive or repulsive. These forces include van der Waals forces, electrostatic forces, steric forces, electrosteric forces, and depletion forces. The interactions between these forces are the primary factors controlling the stability of colloidal systems.