404 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ships of concentration, vapor pressure, flammabili- ty, and solubility will be explained, and formula- tions specifically directed to the use of these propellants in personal and other products pre- sented. SOCIETY OF COSMETIC CHEMISTS FRONTIERS OF SCIENCE LECTURE Theory in chemistry Roald Hoffmann, Ph.D., Department of Chemistry, Cornell University, Ithaca, NY 14853 The motion of the electrons in a molecule is behind every physical, chemical, and biological property of a molecule. The most easily perturbed, the least tightly bound electrons are most important in determining these properties. Such electrons move in "frontier" orbitals. An account of the frontier orbitals and their role in determining the geometry of molecules and the course of chemical reactions will be given. SCIENTIFIC SESSION IV Percutaneous transport of antihistamines Lawrence H. Block, Ph.D., and Samir K. Gupta, School of Pharmacy, Duquesne University, Pitts- burgh, PA 15282 Percutaneous penetration in vitro was followed temporally for selected antihistamines: chlorpheni- famine, diphenhydramine, pheniramine, and pyri- lamine. For these compounds, derreal transport was a function of solute lipophilicity. The permeability constants, diffusion constants, transport fluxes, and computed time lags were functions of the solute octanol/buffer partition coefficients. The use of guinea pig skin and rat skin preparations in these studies led to additional observations: (1) epidermal separation was achieved readily with ammonium thiocyanate (2) derreal transport was comparable to that achieved with skin prepared with ammo- nium hydroxide or stripping and (3) guinea pig skin preparations yielded results more consistent than rat skin preparations. A review of silicon chemistry for the cosmetic chemist Michael S. Starch, Dow Corning Corp., 2200 W. Salzburg, ffC40B00, Midland, MI 48640 Since their first commercial skin care application in the early 1950's, silicones have become known to the personal care formulatot for their unique chem- ical and physical properties. These properties have led to applications in virtually every class of per- sonal care products, including antiperspirants, cos- metics, hair care products, and skin care products. In order to explain the properties of silicones, a review of silicon chemistry will be presented. The similarities and differences between carbon and silicon chemistry will be discussed, and the unusual properties of siloxane polymers will be explained in terms of the differences between siloxane bonds and the carbon-carbon bonds in organic polymers. Many of the important physical characteristics of silicones will be shown to be a direct consequence of the peculiarities of siloxane chemistry. A brief review of the industrial synthesis of silicones will be given, with special emphasis on silicones of interest to cosmetic chemists. Also, the chemical and physical properties of silicones will be related to potential benefits in a variety of product catego- ries. Low-energy emulsifications. Part VI: applica- tions in high-solids emulsions T.J. Lin, Ph.D., and Y. F. Shen, 628 Enchanted Way, Pacific Palisades, CA 90272 Low-energy emulsification (LEE) is a technique by which thermal and mechanical energies are selec- tively applied to only a portion of the emulsified components at certain emulsification stages. By applying far less energy than the conventional hot process, LEE can not only reduce energy costs, but can also significantly reduce cooling time and increase production efficiency. Frequently, the use of a refrigerated system can be completely elimi- nated through the application of LEE in commer- cial processing of cosmetic and pharmaceutical emulsions. Although LEE has proven to be very useful in processing a wide range of emulsions, it has been difficult in the past to apply it to O/W emulsions having solid contents greater than 30% because of the potential phase inversion problems. Phase inversion of the concentrate often leads to poor emulsification and poor stability. By using a new technique of double withholding, LEE can success- fully process a wide range of relatively high solids emulsions while avoiding the common phase inver- sion problems. The athymic nude mouse grafted with human skin as a model for evaluation of radiolabeled cosmetic ingredients Robert V. Petersen, Ph.D., College of Pharmacy, University of Utah, Salt Lake City, UT 84112 During recent years considerable attention has been directed toward transdermal delivery as a means of administering biologically active chemicals to the body. As a result, a large body of information has

ABSTRACTS 4o5 accumulated relative to the permeability of skin and the effects of various permeation enhancers on diffusion into and through the skin. The potential impact of such information on the cosmetics indus- try is obvious. One problem for such studies is that an ideal model does not exist. Various animal studies, human studies, and in vitro diffusion stud- ies all have drawbacks which limit their usefulness. Although still not ideal, the use of the nude mouse onto which human skin has been grafted has many advantages. In this model the human skin maintains most of its inherent qualities and can be used to study permeation of radiolabeled compounds by means of autoradiography, tape-stripping, or simi- lar analytical methods. Results indicate that a number of compounds are capable of permeating into or through the epidermis. Electron spin resonance as a possible new technique for characterizing the fluidity of cosmetic semisolid bases J. K. Lim, Ph.D., J. N. Dalal, and N. S. Dalal, School of Pharmacy, Medical Center, West Vir- ginia University, Morgantown, WV 26506 An investigation was made for the possibility of using electron spin resonance (ESR) as a new technique for characterizing the fluidity (viscosity) of cosmetic semisolid bases. Currently used meth- ods of fluidity (viscosity) measurements do not normally yield consistent results for semisolid bases the inconsistency is related to the different ways of applying stress to a sample during measure- ments. ESR was selected because it can provide information on molecular motion without actually (mechanically) disturbing a sample. The present study suggests that ESR has the potential .for developing into a quick (a few minutes per sample), sensitive (a few milligrams of sample needed), nondestructive, and reliable method for characteriz- ing fluidity of semisolid bases. Details of the methodology and its potential will be demon- strated by application to 4 semisolid bases, 3 belonging to the polyethylene glycol (PEG) family and petrolatum, and the advantages and possible shortcomings of this method will be discussed. Germall II and Germaben II: a significant advance in cosmetic preservation William E. Rosen, Ph.D., Sutton Laboratories, Inc., 116 Summit Ave., Chatham, NJ 07928 In spite of increased sophistication of cosmetic scientists in preventing microbial contamination of cosmetic products, the battle to formulate safe, well-preserved cosmetics is far from won. Germall II (Diazolidinyl Urea), the newest and most active member of the Germall (imidazolidinyl urea) family of antimicrobial preservatives, retains the safety of Germall 115 (Imidazolidinyl Urea), and also pro- vides enhanced activity against mutated bacteria, yeast, and mold. The physical, toxicological, and microbiological properties of Diazolidinyl Urea will be described, and applications to cosmetic formulations will be discussed. Diazolidinyl Urea, a combination of Germall II and parabens, is a complete broad-spectrum preservative in clear liq- uid form. The properties of Germaben II will be described, and applications will be presented which stress economy and convenience of use.