352 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS may not be surface active, is often a technique for improving emulsion stability by mechanical means. The use of two or more surface- active agents in one formula, to accomplish the synergistic effects just mentioned, can perhaps be considered a trend. While ex- perience has proved synergistic ef- fects must occur in certain empiri- cally devised formulas, it seems that only recently has there been any recognition of the possibility of a scientific basis for such combina- tions. Prediction is still difficult the combination may possess the desired properties of both agents, or the undesired ones, or the good may cancel out the bad. Obviously anionic and cationic agents should not be used together, but there are many examples of combinations of agents that are compatible. Thus in formulating a liquid bubble bath, it has been found advantageous to use an alkyl aryl sulfonate or a fatty alcohol sulfate with fatty amides. The use of a small amount of W/O emulsifier in an O/W for- mula often exerts a stabilizing ef- fect the reverse is also true, as most emulsions of good stability seem to contain small amounts of both phases. Data on interfacial tension measurements of combina- tions gave us a lead on that. C. om- binations of synthetics with soap are increasing in number, despite the almost inevitable loss of some foam- producing value. The solubilizing effect of one synthetic on another is often used to give clarity or to pro- mote stability or ease of dispersion. The ability of certain surface- active agents to dissolve essential oils, such as water-insoluble per- fume oils, and to carry the dissolved oil into an apparently clear solution in water, is an interesting property. Among these products are certain of the fatty amides and some of the polyoxyalkylated fatty acids and their esters. Use in colognes, after- shave lotions, theater sprays , and pine oil bath oils is well known. For cosmetic products requiring foaming properties, the fatty alcohol sulfates (24), the alkyl aryl sulfo- nates (10), some of the fatty amides and the amine soaps compete with normal soaps (12, 16). But where non-foaming detergency is required, as in cleansing creams and lotions, mineral oil combined with a non- ionic ester or non-foaming fatty amide emulsifier is indicated. Since the time of contact with the skin is short, the limitations of skin irrita- tion effects is less important in shampoos, bubble baths, hair wave lotions, and the like. It is obviously more important in shaving creams and products that are used under conditions involving stringent me- chanical action, even though they may be removed wi thin a few minutes. In products involving hours of con- tact, all ingredients are contributory (19). The net result is that the number of surface-active agents that can be considered for utilization in- creases as we go from emulsion cream formulation to detergent and foaming types of cosmetic items. Solid, water-free cosmetic prod- ucts such as lipstick, rouge, and face

SURFACE-ACTIVE AGENTS powder seldom utilize surface-active agents. The important exceptions include powdered detergents and bubble bath items. Yet surface- active agents occasionally have some properties, such as solubilizing ac- tion on dyes and dispersing action for pigments, or antifoam action, that indicate potential value in the production stages. It is generally a case of balancing desirable against unwanted properties. No one product can have all the properties desired by all chemists, even for a specified end usage. That is, incidentally, one reason why there is the trend toward syn- ergistic combinations. It is evident that the cosmetic chemist must not only work with surface-active agents but also must choose those most likely to work for him.' Dermato- logic aspects, as evidenced by patch tests on raw material as well as finished product, are one of his most important guides. Classifications of surface-active agents by chemical structure and by major fields of usage (e.g., emulsifier, detergent, etc.) further serve as a means of selecting logical agents with which to work. And last, but not least, articles in the scientific literature as well as the suggestions on formulation fur- nished by suppliers of cosmetic raw materials can often be of real help on specific problems. BIB LIOGKAPHY (1) .Adam, N. K., "The Physics and Chem- istry of Surfaces," Clarendon Press, Oxford, 3rd Edition (1941). (2) Beeler, E. C., "Hydrophilic Ointments IN COSMETICS 353 and Bases," Bull. Natl. Formulary Comm., 10, Nos. 8 and 9 (1943). (3) Benaglia, A. E., Robinson, E. J., Utley, E., and Cleverdon, M. A., "The Chronic Toxicity of Aerosol OT," •e. Ind. hryg. Tox., 25, 175 (1941). (4) Cuppies, H. L., "List of Commercially Available Wetting, Dispersing and Emulsifying Agents," U. S. Dept. Age., Bur. Ent. & Plant Quarantine, Bull. E-504 (June, 1940). (5) deNavarre, M. G., "The Chemistry and Manufacture of Cosmetics," D. Van Nostrand Co., New York (1941). (6) Dodd, M. C., Hartmann, F. W., and Ward, W. C., "Surface Active Agents as Ointment Bases," y. /Im. Ph. /I., Sci. Ed., 35, 33 (1946). (7) Dueruling, W. W., "Wetting Agents. New Synthetic Chemicals of Use in Finer and More Efficient Dermatologi- cal Therapy," zlrch. Dermatol. Syphilol., 43, 264: (1941). (8) Duefee, G. R., "Skin Irritation Studies on Selected Subjects," ]roe. Sei. Sec. Toilet Goods ./tssn., No. 7 (May 16, 1947). (9) Goldsmith, H. A., "Polyhydric Alcohol Esters of Fatty Acids. Their Prepara- tion, Properties and Uses," Chem. Rev., 33, 257 (1943). (10) Harris, J. C., "Shampoo Formulation," /Ira. ]erfumer & Essent. Oil Rev., 48, 54 (Nov.) 71 (Dec.) (1946). (11) Hermann, F., Sulzberger, M. B., and Baer, R. L., "New Penetrating Ve- hicles and Solvents," Science, 96, 451 (1942). (12) Hilfer, H., "Soapless Detergents," Drug & Cosmetic Ind., 58, 646 (1946). (13) Hollenberg, I. R., "Emulsion Tech- nology," Ibid., 59, 340 (Sept.) 644 (Nov.) (1946). (14) Lane, C. G., and Blank, I. H., y..//m Med./Issoc., 118, 804 (194:2). (15) Macias-Sarria, J., "Sodium Lauryl Sul- fate as an Emulsifier,"/Im. ]etfumer & Essent. OilRev., 48, 61 (1946). (16) McCutcheon, J. W., "Detergents. Syn- thetic rs. Soap," Soap & San. Chem., 37, 3742 (Sept., 1946). (17) McCutcheon, J. W., "Synthetic Deter- gents. Main Types, Uses, Properties and Prospects," Chem. Indus., 61, 811-24, (Nov., 1947). (18) "Medicinal Uses of Soap," edited by Dr. Morris Fishbein, J.P. Lippincott Co., Philadelphia (19'[6). (19) Schwartz, L., "Protective Ointments and Industrial Cleansers," Medical Clinics of North America, 1195 (July 1942). (20) Schwartz, L., and Peck, S. M., "Cos-