OIL I)EI'OSITION ON SKIN 615 .•' . ...:/ ß • • • ).'• ..• : ... . ":•:...•7 • .... . ..• .. . . . ..,:. .. Figure 2m. Lanolin derivative "B '• . •2 7.?....: -: • •. •.. '::'•'•'4 3k.: :- .:•,- .. .• . •.• ? • :.. ....... .?: .... ... • .... •.• ..• •:":• .:.? .. , ..... . : :•c -':• •L • Figure 2n. Lanolin derivative "C" Figure 20. Cottonseed oil Figure 2p. Corn oil Figures 2a-2p. Effect of various oily liquids in aqueous dispersions, maintained at 40øC, on skin coverage of deposited oil fihns The spreading coefficient has been used as an indication of spread- ability of one immiscible liquid over another (14). Spreading coefficient values were calculated from the relation' Spreading coefficient = ST (water) -- ST (oil) -- IFT (water-oil) The surface tension (ST) and interfacial tensions (IFT) were ob- tained with the DuNuoy tensiometer. The procedure consisted of measuring the surface tension of the aqueous phase which was then layered gently with the oil phase the interfacial tension was then determined. The surface tension of the oil was determined separately and the spreading coefficient calculated from these values after correc- tions were made for density and ring size.

616 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS RESULTS AND DISCUSSION The most extensively used ingredient in topical and cosmetic formu- lations is mineral oil. The affinity of mineral oil to hair from a shampoo formulation was demonstrated by Goldemberg (15). Taylor (11) re- ported that bath oils formulated with mineral oil were superior to bath oils prepared with vegetable oil. Neifher researchers stated the type of grade of the mineral oil used in their investigation. Mineral oils in given viscosity ranges may appear to be quite similar, yet can be significantly different in composition, physical properties, and behavior on the skin (16). These oils contain paraffinic (20-47%) and naphthenic (53-83%) fractions, and significant variations in relative percentages of these two fractions of hydrocarbons may exist in oils having similar viscosities. Table I demonstrates the effect of the grade or composition of mineral oil in aqueous dispersion, maintained at 40 øC, on oil deposition on the skin after immersion for 15 minutes. From these results it would ap- pear that the amount of oil deposited is affected by the grade of mineral oil. With increasing viscosities there appears to be a decrease in the amount of oil deposited. Furthermore, the viscosities appear to be directly related to the naphthenic content. An increase in the naph- thenic content of the mineral oil results in an increase in viscosity and an apparent decrease in affinity to skin. This is exhibited in Figs. la-lc. No correlation appears to exist between spreading coefficient values obtained for the various grades of mineral oil and the amount or coverage of the deposited oil film (Table II). Table III illustrates the effect of various oily liquids dispersed in water maintained at 40 øC on oil deposition on skin after immersion for 15 minutes. Figures 2a-2p record the coverage of skin achieved by the deposited oil films from aqueous dispersions of the various oily liquids. A direct correlation may be noted between the spreading coefficient values obtained for the isopropyl ester series and the amount of oil de- posited on the skin (Table IV). With increasing spreading coefficient an increase may be noted in the amount and coverage of the skin by the deposited oil film. In the sebacic acid esters series, significantly different spreading co- efficient values were recorded for di-butyl and di-octyl esters. However, the amount of oil deposited appears to be the same. Figures 2e and 2f exhibit better coverage of skin from aqueous dispersions of di-butyl sebacate than from di-octyl sebacate. The best skin coverage was re-