FATTY ACIDS AND DERIVATIVES IN COSMETICS 227 of emulsion stability , thickening power, opacifying power, texture of emul- sion and appeara:,ce. The glyceryl mono/31eate showed less binding or thickening charac.teristics but nevertheless gave thin but stable emulsions. The glyceryl mon•ostearate and the laurate gave relatively poor systems and the emulsion broke within several hours. The monoglyceride of the mixed fatty acids qf oleic, palmitic and stearic gave additive characteristics and performance.' The percentage of palmitic acid in the mixed mono- glyceride appeared to dominate the performance characteristics. In system No. 2 of oil and monoglyceride, the viscosity of the system was directly in line with the increase in the chain length of the fatty acid used with the glyceryl monolaurate giving the thinnest gel and the glyceryl monostearate giving the thickest gel. Glyceryl mono61eate, however, proved to be completely soluble in the oil gil•ying a clear and homogeneous solution. In system No. 3 of vegetable oil and monoglyceride the results were fairly consistent With those obtained in system No. 2. Perhaps the viscosities and gelling properties of the palmitic and the myristic were somewhat more marked than those observed with mineral oil. In system No. 4 where small amounts of soap could be formed due to the presence of alkali and fatty acids, unusual thickening and suspending characteristics were noted for the myristic and palmitic monoglyceride. The combined effects of the monoglyceride and the soap of those fatty acids appeared to give thicker and smoother creams than those from stearic, oleic and lauric. Considering the monoglycerides of saturated fatty acids are stable to oxidation, color and odor development and can be easily and economically prepared, the monoglycerides of myristic and palmitic acids appear to hold promise for more extensive use in both oil and water systems. In the oil system alone, however, where miscibility may be a desirable factor, the monoglyceride of oleic acid can be effectively used. In the thickening, gelling or opacifying of oil systems the monoglycerides of stearic, palmitic and myristic can be used rather well. In line with the evaluation of the monoglyceride, our laboratory also prepared the triglycerides of the same fatty acids. The triglycerides were tested for their solubility, suspending and gelling characteristics in both mineral and vegetable oils. In mineral oil, for example, the triolein was completely miscible. The saturated fatty acid glycerides showed that the palmitichad greater gelling properties than stearic, which in turn was greater than the myristic ester. The same degree of gelation was possible in the given system even with the lauric ester, but only at greater concentrations of the glyceride. Results are tabulated in Fig. 1. In the vegetable oil system the palmitic and rhyristic esters gave superior gelling and suspending characteristics than th'• stearic, which in turn was

228 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS lOO 80 •6o • 40 30 2o 0 5 10 15 20 25 30 35 % TRIGLYCERIDE IN MINERAL OIL •'IGURE ]. greater than the lauric. The crystal pattern of the trilaurin, however, was found quite objectionable to the preparation of smooth, creamy liquids or pastes. See Fig. 2. In the triglycerides, as in the mono- and diglyceride mixtures, advantages of the palmitic and myristic acid esters were clearly observed which suggest their consideration for thickening, creaming or opacifying mineral or vege- table oil systems over the other fatty acid glycerides. In the consideration of glycerides and their possible uses and application, perhaps we can consider a series of high lauric-containing triglycerides which have come to be known as Hard Butters. Their primary use has been in the edible field, initially as a substitute for cocoa butter, but later considered on their own merits because of the versatility and flexibility which this group of products possesses. Their industrial use is just begin- ning to be explored and promises to have a wide variety of possibilities. Hard Butters were initially prepared by the pressing operation of kernel type oil such as coconut or palm kernel, where the oil under controlled temperature conditions was separated into a liquid and solid component. The solid fraction was used as the substitute for cocoa butter. Some years later reconstituted glycerides (15-17) were prepared from