X-ray investigation of the structure of transparent oil-water disperse systems. I

Abstract

The spacings of X-ray diffraction bands were studied for systems of oil, water and soap which had been titrated to transparency and fluidity by the addition of certain aliphatic or alicyclic alcohols. These systems were non-birefringent. Two systems were investigated in some detail; one, in which the oil was the continuous phase (electrically nonconducting), and the other, in which the aqueous solution was the continuous phase (electrically strongly conducting). It was shown that, with soap solutions of less than 27% in the water phase, the spacings of the X-ray bands gave strong support to the concept that the structure consisted of close-packed uniform water spheres in oil or close-packed uniform oil spheres in water. Each droplet is considered to be stabilized by a mixed monolayer of the soap-alcohol molecules. By changing the soap-alcohol concentration, the diameters of the spheres were varied from approximately 100 Å to 550 Å, at which dimensions a strong Tyndall effect was observed. By changing the oil-water ratio, the spacings of the X-ray bands suggested that the distance between the spheres of oil or water was being varied. Conditions could be so chosen that the spheres were “squashed,” this giving rise to broad diffuse X-ray bands and to an anomalous electrical conductivity of the oil-continuous systems. In those systems which contained very highly concentrated soap solutions (38%), the X-ray measurements were better interpreted as fitting a struture of short cylinders or short lamellae of the soap-alcohol molecules with oil and water between the layers.