Zur Theorie der Stabilität von Emulsionen
Hermann Lange

Synopsis

Comments on the theory of emulsion stability. Existing concepts of the mechanism of emulsion stabilizers are summarized. Inhibition of creaming and of coalescence must be differentiated. Whether a given system forms an o\/w or a w\/o emulsion depends primarily on the ratio of the velocity of coalescence of the oil and water droplets, unless the volumes or viscosities of two phases differ greatly. In this connection, the velocities of coalescence during formation of the emulsion play an important role; these differ from the velocities in the finished formulation since no equilibrium between distribution and adsorption of all components exists during formation. Further examination of influences which reduce coalescence under dynamic and static conditions indicates that these may be divided into those which preferentially stabilize oil or water droplets. This fact forms a basis for a physico-chemical interpretation of the HLB system and of the Bancroft rule on the relationship between the distribution equilibrium of the emulsifier and of the emulsion type. In conclusion, the conditions for true spontaneous emulsification are discussed; this probably occurs only if the system is initially not in distribution equilibrium.

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