CONTINUOUS MIXING AND PROCESSING 653 ity and predictability of mixing and contacting can bc achieved by using the device. Controllability of the drop size by changing the flow rate and narrow drop size distribution of the dispersion allows one to better predict the inter- facial area of the dispersion, an important parameter in heat and mass trans- fer operations and in heterogeneous chemical reactions. If fast separation of phases in the dispersion is required after reaction, heat and mass transfer op- erations, the drop size can be controlled so that emulsification is minimized. Spccific advantages of using the device include: no maintenance cost, low operating cost, fast and simple processing, facilitation of on-line automatic control, reproducibility and predictability, consistency in product quality, and no noise. (Received December 12, 1972) (1) (2) (3) (4) (5) (6) (7) (8) (9) (lO) (11) REFERENCES Bor, T. P., The Static Mixer as a chemical reactor, Brit. Chem. Eng., 7, 20-1, July (1971). Chen, S. J., Fan, L. T., Chung, D.C., and Watson, C. A., Effect of handling methods on bulk volume and homogeneity of solid materials, J. Food Sci., 36, 688-91 (1971). Devellian, R. D., Continuous predictable performance with motionless mixers, Auto- mation, 2, 15-7, February (1972). Devellian, R. D., and Wong, C., Continuous inline preparation of paper and board coatings, Tappi, 55, 97-101 (1972). Grace, C. D., Static mixing and heat transfer, Chem Process. Eng., 7, 52-3, March (1971). Macdonald, A. R., Static Mixer technology as applied to the production and applica- tion of adhesives and sealants, J. Adhesives Sealant Council, 1, 154-62 (1972). Mack, W. A., New approaches in equipment design, Presented at PIA Annual Conf., Steven Inst. Tech., Hoboken, N.J., 1972. Hartung, K. H., and Hiby, J. W., Comparison of turbulence promoters for inline mix- ing, Presented at 4th International CHISA Conf., Prague, Czechoslovakia, 1972. Olson, R. M., Essentials of Engineering Fluid Mechanics, 2nd ed., International Text- book Co., Scranton, Penn. 1966, pp. 224-31. Calderbank, P. H., Mass Transfer, in Uhl, V. W., and Gray, J. B., Mixing-Theory and Practice, Academic Press, New York, N.Y., 1967, pp. 5-18. Middleman, S., Drop formation in the Kenics Static Mixer system, Kenics Research Report No. 2001 (1970).

J. Soc. Cosmet. Chem., 24, 655-662 (September 16, 1973) Some Techniques for Microbial Control ß M f 'gPla anu actann nts FREDERICK W. DAWSON, B.S.* Presented December 11, 1972, New York City Synopsis-MICROBIAL CONTAMINATION problems are a rapidly growing concern to COSMETIC MANUFACTURERS. While preservatives may limit the growth of low levels of contaminants, large numbers of microorganisms can overwhelm the preserva- tive system. The primary sources of contamination present in cosmetic preparation are MAKE-UP WATER and RAW MATERIALS. Microbial organisms from the city water supply can mttltiply rapidly in the aleionizing columns and seed the entire distribution system. Various locations within the manufacturing process then act as niduses of infection which continually shed organisms into the system. Techniques for reducing microbial levels in deionized water systems such as formalin decontamination, recirculation, point-of-use filtration, and principles of clean system de- sign are discussed. Design parameters for FILTRATION SYSTEMS capable of sterilizing other raw materials such as waxes, petrolatum, and oils, at flow rates of 8 kg/min and costs of 9 cents/kg, are presented. INTRODUCTION The problem of microbial contamination in tofietries and cosmetics is of concern to the industry, the consumer, and regulatory agencies. Pathogenic organisms such as the Pseudomonas species have been implicated as the etio- logical agents of various conditions ranging from minor skin infections to cor- nea1 ulcers and fatal septicemias. The presence of enteric organisms (Entero- bacter) should also be cause for alarm. Opportunistic pathogens such as Staphylococcus, Candida, and Corynebacterium are also undesirable in cos- metics. While these groups of organisms may not affect the normal population, they are capable of causing disease in the very young, the aged, and in persons with impaired immunological defense mechanisms. Pseudomonas organisms are not solely a health hazard. They represent a potential economic loss in terms of product spoilage. They have been respon- * Millipore Corp., Bedford, Mass. 01730. 655