RADIOISOTOPES IN DETERGENT AND COSMETIC RESEARCH 331 followed in respect to motor speed, position and angle of stirring, amount of additive, temperature, time of stirring and shape of vessel. With use of a scintillation counter and gamma emitting isotopes (so that adsorption corrections are not necessary), techniques have been developed that are faster, more accurate and are far more sensitive than usual analytical methods. Stability of emulsions can also be evaluated using radioisotopes (19). By tagging one component in an emulsion and by radioassay along the vertical side of the vessel containing the mixture, the gradient of radio- activity obtained from the surface of the mixture to the bottom is an excellent index of homogeneity. Quite often, long before visual signs of separation occur, the gradiation of radioactivity has shown the emulsion mixture to be separating. Therefore the technique permits quicker evaluation of lotions and creams in respect to their stability toward separa- tion. SummARY Uses of radioisotopes in detergent and cosmetic research is demonstrated, with specific examples being given of radiotracer techniques applied to various problems. In the examples shown, the use of radioisotopes was stimulated by either lack of routine analytical techniques suitable for assay of the desired material or very high costs of experimental methods by use of these tech- niques. Manpower hours were saved and valuable research knowledge was gained which aided in product developement and improvement. REFERENCES (1) Nucleonics, 15, (9), 118 (1957). (2) Allison, J. B., Nelson, M. F., and Hilf, R., to be published. (3) N.Y. State Dental yourhal (June-July), 274 (1953). (4) "Radioactivity at Work," Vol. 7 (December), Nuclear Science and Engineering Corp., Pittsburgh (1957). (5) Nelson, M. F., and Stewart, D., y. Soc. Cosmetic Chemists, 7, 122 (1956). (6) Stam, P. B., and White, Jr., H. J., Textile Research 24, 789 (1954). (7) Nelson, M. F., Nucleonics, 14, (5), 43 (1956). (8) Nelson, M. F., and Stewart, D., unpublished results. (9) Allison, J. B., Zullo, R. J., and Nelson, M. F., unpublished results. (10) Sheneane, I., and Nickerson, M., Fed. Biol. $oc. Proc., 13, (1), 404 (1954). (11) Davis, W., Miya, T. S., Edwards, L. D., y. Arm. Pharm. Atssoc., $ci. Ed., 45, 60 (1956). (12) Meshbane, A., y. $oc. Cosmetic Chemists, 3, 291 (1952). (13) Lux, R. E., and Christian, J. E., y. Arm. Pharm. Atssoc., $ci. Ed., 40, 160 (1951). (14) Urakami, C., and Christian, J. E., y. Arm. Pharm. •'lssoc., Sci. Ed., 42, 179 (1953). (15) Banks, Jr., H. O., Nucleonics, 13, (12), 62 (1955). (16) Nelson, M. F., Afonsky, D., and Quigley, G., unpublished paper, presented at Interna- tional Association of Dental Research spring meeting (1957). (17) Harris, J. C., Kamp, R. E., and Yanko, W. H., "Improved Radioactive Tracer Carrier for Metal Cleaning Studies," ASTM Bulletin No. 170, 82, December (1950). (18) Hensley, J. W., Iron Atge, 170, 151 (1952). (19) Hensley, J. W., Plating, 40, 366 (1953). (20) Ashcraft, E. B., "Use of Radioactive Tracers in the Study of Soil Removal and Deter- gency in Symposium on Radioisotopes," ASTM Special Technical Publication No. 215. (21) Segura, G., Chemistry andIndustry, 1270 (1953).

332 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (22) Ridenour, G. M., and Armbruster, E. H.,/lm. y. Public Health 42, 138 (1953). (23) Ridehour, G. M., and Armbruster, E. H., Soap & San. Chem., 28, 83 (1952). (24) Lambert, J. M., Nucleonics, 12 (2), 40 (1954). (25) I.ambert, J. M., unpublished studies. (26) Hensley, J. W., et al., y./lm. Oil Chem.'Soc., 32, 138 (1955). (27) Nuclear--Chicago Corporation, Chicago, Ilk (28) Hensley, J. W., personal communication. (28) Harris, J. C., Kamp, R. E., and Yanko, "Application of the Radiotracer Technique to Metal Cleaning," ASTM Bulletin No. 158, May, 49 (1949). FLUID MIXING OF coSMETIC FORMULATIONS By J. Y. Onr)suE* Presented November 20, 1958, New York City EFFECTIVE VLUID MIXING is desired in every phase of cosmetic manufacture. Mixing is involved in a wide variety of processes and the principles and criteria of performance for each process have unique properties. It is desirable to first consider the type of flow pattern produced by mixing impellers and the fluid mechanics involved in these flow patterns. Then we may look at the requirements of various mixing processes to see which elements of the fluid regime produced by the mixer are most impor- tant in the particular process under consideration. One of the key factors in selecting a mixer is to accurately define the process specifications. Once the role of the mixer is established, then we may examine the various functions the mixer may have in the process and decide on the final process design. As an aid in setting up mixer specifications, it is of interest to review various quantitative specifications to examine the effects of mixing vari- ables in these processes. One of the basic classifications of mixing processes is into the number and type of phases being contacted. Thus, we may first classify mixing processes into the following areas: A. Single-phase systems 1. This includes blending of miscible liquids, homogeneous chemical reactions and other types of single-phase processes. B. Two-phase systems 1. Liquid-liquid contacting, which includes physical dispersions such as emulsification and liquid-liquid extraction. * Mixing Equipment Company, Inc., Rochester 11, N.Y.