EMOLLIENCY AND CHEMICAL STRUCTURE 649 Table XIV Hydrocarbons Approx Viscosity Mol Wt Carbons (Lotion)(cps) Mineral oil (65/75) Squalene Squalane White petrolatum Paraffin wax (130 øF) Initial Slip (Scale 1-5) Paraffin 4.0 Mineral oil 4.3 Petrolatum 5.0 Squalane 5.0 Squalene 5.0 335 234- 9000 411 30 8680 423 30 6140 500 35 6810 400 6430 End Feel (Scale 4-20) Paraffin 7.0 Petrolatum 10.0 Squalane 14.3 Mineral oil 16.5 Squalene 17.3 the influence of unsaturated bonds and additional groups such as the hydroxy. Polar groups often reduced the value of cosmetic emollients. The poor performance shown by the lanolin alcohols in this lotion (per- haps due to their high melting point) may surprise some formulators however, their usual cosmetic use is for other properties than skin feel. The emollient value of HYDROCARBONS apparently depends greatly on their melting points (Table XIV). Solid paraffin (mp 55øC) gives very poor results, semisolid petrolatum gives fair results, and me- dium viscosity mineral oil was quite good. The saturated squalane gives an End Feel slightly poorer than medium viscosity mineral oil, whereas the unsaturated squalene gives excellent End Feel. The ideal emollient (structurally) would appear to be one with a fairly long hydrocarbon chain having some unsaturation and branching, as illustrated perhaps by squalene. The SFI of squalene was 5.0/17.3. ANIMAL AND VEGETABLE OILS were also evaluated (Table XV). Lanolin oil (also known as "liquid lanolin") gave one of the lowest End Feel scores of any material tested in this study. Castor and mink oils (both highly unsaturated) also gave poor scores on the other hand, squal- ene and Jojoba oils (also highly unsaturated) produced extraordinarily high scores. Triglyceride oils generally performed more poorly than the hydrocarbons or high molecular weight esters, both o[ which are "oilier" in their molecular structure. The poor influence of polar (hydroxy) groups is seen once again in this series the triglyceride oils did not per- form as well as the fatty ester oils.

650 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table XV Animal and Vegetable Oils Approx Composition Mol Wt Viscosity (Lotion) (cps) Animal Egg oil Lanolin oil Mink oil Squalene Squalane Vegetable Jojoba Peanut Castor Safflower 62% glycerides, 33% phosphates, 5 % sterols ... Cholesterol, triterpenes, fatty acids ... C•4-C20 unsaturated triglycerides 852 Coo unsaturated aliphatic hydrocarbon 411 Ca0 saturated aliphatic hydrocarbon 423 Liquid wax (C20-C• esters)(half unsat.) 609 Triglycerides 864 90% ricinoleic triglyceride 935 Highly unsaturated triglycerides 942 6760 4680 9800 8680 6140 6880 10,010 6560 11,300 Initial Slip (Scale 1-5) End Feel (Scale 4-20) Castor 3.5 Lanolin oil 6.5 Jojoba 3.5 Castor 11.4 Mink 3.5 Mink 13.0 Egg 3.8 Egg 14.3 Peanut 4.0 Squalane 14.3 Safflower 4.0 Peanut 15.5 Lanolin oil 4.5 Safflower 15.5 Squalane 5.0 Squalene 17.3 Squalene 5.0 Jojoba 18.0 LANOLIN DERIVATIVES performed erratically (Table XVI). As previously noted, liquid lanolin gives very poor End Feel (6.5). Pure "lanolin alcohols" and lanolin alcohols ricinoleate are next (about 12.0), while lanolin itself gives a score of 15.8, substantially better than the con- trol lotion containing no emollient, but still not very good in comparison to the better emollients. Other lanolin derivatives (the acetate, a hydro- carbon extract, and isopropyl lanolate) gave fairly good results (16-17). The best of this series was isopropyl lanolate, which produced an End Feel almost 50% better than lanolin alcohols themselves. Table XVII is a regrouping of previous data to show all the ISO- PROPYL ESTERS together. These were often the best of each series originally tested. Note that isopropyl ricinoleate, with its hydroxy group as well as double unsaturation, and the linoleate, also with two unsatu- rated bonds, performed quite poorly. Isopropyl azelate, an odd-carbon (C9) fatty acid ester, gave a sligh:tly better result than the sebacate, an even-carbon (C•0) fatty acid ester of approximately the same molecular