ABSTRACTS 47 of the predictive accuracy of these relatively small panels to wide scale consumer usage. Effect of polyols on stability of suspensions containing nonionic wetting agents Joel L. Zatz, Ph.D. and Ru-Yun Lue, Rutgers University College of Pharmacy, P.O. Box 789, Piscataway, NJ 08854. In an earlier study, it was shown that propylene glycol caused flocculation in sulfamerazine suspen- sions containing a nonionic surfactant as wetting agent. The present investigation was intended as a more in-depth inquiry into the influence of polyols on suspension stability. Polysorbate 80 and poly- sorbate 20 were employed as wetting agents for sulfamerazine, salicylamide and butamben suspen- sions. After preliminary investigation using several polyols, sorbitol was selected for detailed study because of its negligible effect on solubility of the suspended drugs. In the absence of sorbitol, all of the suspensions were deflocculated and they settled to a non-redispersible cake. The addition of sorbitol resulted in an increase in sedimentation volume and prevented cake formation. The concentration of sorbitol needed depended on the solid and on the surfactant. Sorbitol effectiveness in preventing caking was enhanced by a rise in temperature or by the addition of a salt, but reduced by an increase in surfactant concentration. Cloud point and surface tension studies implicated a reduction in polyoxyethylene hydration by sorbi- tol as a key factor in counteracting deflocculation of the suspensions. Cloud points correlated extremely well with sulfamerazine suspension data. They indicate the trends observed with other suspensions. Physical stability assessment of emulsions and related disperse systems George Zografi, Ph.D., University of Wisconsin School of Pharmacy, Madison, WI 53706. Most measurements of disperse system physical stability fall into two categories: 1) application of stress conditions which accelerate instability, followed by attempts to predict long-term stability and 2) use of techniques which are very sensitive to the small changes which might occur during short periods after preparation of the disperse system. Both approaches may be faulty. The first may eliminate good products because of excessively applied artificial stresses, and the second may only indicate very bad systems because of inadequate sensitivity. Before one can develop techniques to properly assess the short and long term physical changes which might take place, it is important to know as much as possible about the physical chemical nature of the processes bringing about change. Phase separation due to coalescence, for example, reflects phenomena quite different from those due to creaming in an emulsion. How a thermal or theological stress used in any test can alter the patterns of physical change is a critical factor in determining its usefulness. This paper discusses a variety of approaches which may be used to understand the causes of disperse system instability and the meaning of the tests we use.

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Book Review MICROBIOLOGY OF HUMAN SKIN, by W. C. Noble. Lloyd-Luke (Medical Books) Ltd., London, 1981. 433 pages. Price $50.00. The author has adequately covered the subject matter so this book should be of great interest to Microbiologists specifi- cally and Cosmetic Scientists in general. This 3rd edition is an updated and modi- fied version of the 1974 (2nd Edition) publication. The content and organiza- tion of the text is the same as the earlier edition. The textbook presents a good update and clarification of the Coryne- form Bacteria in Chapter 4, including a revised taxonomy. The organization of the material is presented well, utilizing the format of.' 1. Skin as a Habitat. II. Microbial Inhabitants of the Skin (arranged by specific groups ie. Coryneform, Micrococcus, Strep- tococci, Fungi, etc.). lll. Ecology of the Skin. The textbook provides an excellent updated reference text and provides a good basic understanding of skin diseases from a Microbiological viewpoint. Minor improvements which could be recom- mended are: expansion of Chapter 11 on Fungi, and expansion of Chapters 17 and 18, which are light in content (although appropriate references are given for the reader who should require more knowl- edge). This book will be useful for students and Cosmetic Scientists and has a good deal of value for those interested in the subject.--O. J. LORENZETTI, PH.D.-- Owen Laboratories.