[Surface activity of emulsifiers. Part IV. Determination of the contact angle at the interface of two liquids].

A method has been worked out for the determination of wetting contact angle formed at the interface of oil/water and/or aqueous and oleaginous solutions of surfactants, respectively. Contact angle proved to be an accurate and well reproducible index. The size of contact angle decreased logarithmically along with the concentration of tensids. Several samples of the emulsifier series tested, induced interfacial tension in 1-1.5%, and the wetting contact angle did not decrease further above this concentration. Correlation and a non-linear regression was found between the contact angle and the interfacial tension.