EVALUATION OF STABILITY RATIO IN OIL-IN-WATER EMULSIONS

The kinetics for emulsion coagulation retarded by the electrostatic re pulsion between droplets in the micron size range was studied. The rat her high electrokinetic potential is provided by the presence of 10(-3 ) M NaOH. The enormous discrepancy between theory and experiment is sh own to be analogous to that of solid suspensions. It was shown that Fu chs theory is invalid for emulsions where the existence of surface rou ghness or heterogeneity is completely excluded. To ensure that the ele ctrostatic barrier is the single reason for the coagulation retardatio n, the use of ionic surfactant adsorption was avoided. This necessary condition causes an increase of the critical thickness h(cr) at which spontaneous disruption of the thin emulsion him occurs. The condition h(cr) < h(max) is formulated as necessary for the examination of slow coagulation theory on emulsions, where h(max)is the distance between t he surface and the electrostatic energy maximum. For micron size dropl ets the predominance of Brownian coagulation over gravitational coagul ation was ensured by the use of a dichlorodecane emulsion.