A Suitable Hydrocarbon for Oil–Water Dispersion Measurements

Abstract

THE measurement of properties of emulsions and of interfacial phenomena is usually complicated by density differences between the ‘oil’ and aqueous phases and by the polarity of the oil. Sedimentation introduces non-uniformity and causes errors which cannot be assessed; creaming, by effectively increasing the concentration and bringing the drops into close contact, increases the rate of coagulation. Stirring or mixing is not usually permissible as it changes the size distribution. To overcome the former difficulty, workers have weighted their oils, often of ‘Nujol’ type, to the same density as that of the continuous phase. Thus, Sibree¹ added tribrom-methane to medicinal liquid paraffin before measuring viscosities. This method is not to be recommended on account of (a) the appreciable solubility of tribrom-methane in water, (b) its slow hydrolysis in aqueous solution, and (c) the introduction of a strongly polar compound. Similar arguments can be given against other weighting compounds, which are usually halogenated hydrocarbons.