The stability of elementary emulsion drops and emulsions

• Published in: Journal of colloid science 1953-01, Vol.8 (4), p.440-451
• Main Authors: Cockbain, E.G, McRoberts, T.S
• Format: Article
• Language: English
• ISSN: 0095-8522
• DOI: 10.1016/0095-8522(53)90028-2

The rates of coalescence of oil and water drops at the oil-water interface have been measured in the presence of soaps, cholesterol, saponin, serum albumin, and polyvinyl alcohol. Interfacial viscosity and tension data have been obtained for some of the systems. With potassium laurate, cetyltrimethylammonium bromide, or sodium desoxycholate as stabilizer, benzene and paraffin drops possess maximum stabilities at concentrations slightly greater than the critical micellar concentration (c.m.c.). Drops of the aqueous soap solutions in a continuous oil medium coalesce very rapidly, in accordance with the preferential oil-in-water emulsifying power of the above soaps. Mixed adsorbed films of cholesterol and potassium laurate at the paraffin—water interface have a greater stabilizing effect than either cholesterol or potassium laurate films alone. The stability of oil drops in aqueous solutions of saponin or serum albumin is very high, but drops of aqueous saponin or serum albumin in a continuous oil phase are stable for only a few seconds, despite the high viscosity of the adsorbed films. It is concluded that the main factor determining stability in all the systems examined is the resistance to wetting of segments of the adsorbed film by the discontinuous phase. An explanation is given for certain empirical rules relating emulsion type to preferential wettability or solubility of the stabilizing agent in oil and water.