ALUMINUM CHLOROHYDRATE 295 ACKNOWLEDGEMENT Journal Paper 9083, Purdue University Agricultural Experiment Station, West Lafayette, IN 47907. Copyright: The Journal of the Society of Cosmetic Chemists. REFERENCES (1) The Merck Index, 9th ed., (Merck and Co., Inc., Rahway, N.J., 1976), p 47. (2) S. L. Nail, J. L. White, and S. L. Hem, Structure of aluminum hydroxide gel I: Initial precipitate, J. Pharm. $ci., 65, 1188-1191 (1976). (3) H. H. Reller and W. L. Luedders, Pharmacologic and toxicologic effects of topically applied agents on the eccrine sweat glands. Part II. Mechanism of action of metal salt antiperspirants, Adv. Mod. Tox. 4, 18-54 (1977). (4) R. P. Quatrale, A. H. Waldman, J. G. Rogers, and C. B. Felger, The mechanism of antiperspirant action by aluminum salts. I. The effect of cellophane tape stripping on aluminum salt-inhibited eccrine sweat glands,J. Soc. Cosmet. Chem., 32, 67-73 (1981). (5) R. P. Quatrale, D. W. Coble, K. L. Stoner, and C. B. Felger, The mechanism of antiperspirant action by aluminum salts. II. Histological observations of human eccrine sweat glands inhibited by aluminum chlorohydrate,J. Soc. Cosmet. Chem. 32, 107-136 (1981). (6) R. P. Quatrale, D. W. Coble, K. L. Stoner, and C. B. Felger, The mechanism of antiperspirant activity by aluminum salts. III. Histological observations of human eccrine sweat glands inhibited by aluminum zirconium chlorohydrate glycine complex,J. Soc. Cosmet. Chem., 32, 195-221 (1981). (7) D. L. Teagarden, J. F. Kozlowski, J. L. White, and S. L. Hem, Aluminum chlorohydrate I: Structure studies,J. Pharm. Sci., 70, 758-761 (1981). (8) G. Johansson, G. Lundgren, L. G. Sillen, and R. Soderquist, On the crystal structure of a basic aluminum sulfate and the corresponding selenate, Acta Chem. Scand., 14, 769-771 (1960). (9) D. L. Teagarden, J. F. Radavich, J. L. White, and S. L. Hem, Aluminum chlorohydrate II: Physicochemical studies,J. Pharm. Sci., 70, 762-764 (1981). (10) P. H. Hsu and T. F. Bates, Formation of X-ray amorphous and crystalline aluminum hydroxides, Min. Mag., 33, 749-768 (1964). (11) F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, 4th Ed., (Wiley, New York, 1980), p 334. (12) R.J. Moolenaar, J. C. Evans, and L. D. McKeevet, The structure of the aluminate ion in solutions at high pH,J. Phys. Chem., 74, 3629-3636 (1970). (13) C.J. Serna,J. L. White, and S. L. Hem, Anion-aluminum hydroxide gel interactions, SoilSci. Soc. Amer. Proc., 41, 1009-1013 (1977). (14) W. Huehn and W. Haufe, Water-soluble basic aluminum compounds, U. S. Patent 2,196,016, April 2, 1940. (15) P. H. Hsu, Aluminum hydroxides and oxyhydroxides, in Minerals in Soil Environments, J. B. Dixon and S. B. Weed, eds., (Soil Sci. Soc. Amer., Madison, Wisconsin, 1977), pp 99-143. (16) J. D. Hem and C. E. Roberson, Form and stability of aluminum hydroxide complexes in aqueous solution, U.S. Geological Survey Water-Supply Paper 1827-A, U.S. Government Printing Office, Washington, D.C., 1967. (17) S. L. Nail, J. L. White, and S. L. Hem, IR Studies of development of order in aluminum hydroxide gels, J. Pharm. Sci., 65,231-234 (1976). (18) D. L. Teagarden, J. L. White, and S. L. Hem, Aluminum chlorohydrate III: Conversion to aluminum hydroxide,J. Pharm. $ci., 70, 808-810 (1981).

j. Soc. Cosmet. Chem., 33,297-307 (September/October 1982) Antimicrobial activity of butylparaben in relation to its solubilization behavior by nonionic surfactants MICHIHIRO YAMAGUCHI, YOSHIO ASAKA, MUNEO TANAKA, TAKEO MITSUI, and SABURO OHTA, Shiseido Laboratories, 1050 Nippacho, Kohoku- ku, Yokohama- shi, 223 Japan. Received October 5, 1981. Presented at the I Ith International IFSCC Congress, Venezia-Lido, Italy, Sept. 23-26, 1980. Synopsis The effect of various nonionic surfactants and other materials on the antimicrobial activity of butylparaben (BP) and its solubilization behavior in cosmetic formulations was nvestigated by equilibrium dialysis technique. The results indicate that the antimicrobial activity of BP in combination with various nonionic surfactants differs according to the type of microorganism. The concentration of free BP is primarily responsible for its antimicrobial activity against Candida albicans, but the total concentration of BP in the system determines its activity against Pseudomonas aeruginosa. The solubilization of BP conforms to Langmuir's adsorption equation in all surfactants used. The combined parameter K•K2, corresponding to the distribution coefficient obtained from the reciprocal Langmuir's plots, relates to the solubilization behavior of BP the more hydrophobic the surfactant used the larger K•K2 value, thus the greater the solubilization of BP. INTRODUCTION Antimicrobial activities of preservatives are often reduced when they are formulated in cosmetics together with certain surfactants. The solubilization of preservative within nonionic surfactant micelies or the formulation of hydrophobic complexes between preservative and surfactant is considered to be the main reason for the reduction of the activity. It is generally claimed that the antimicrobial activity of preservative in aqueous surfactant solution is governed by the concentration of free preservative (1,2,3) which is not solubilized within surfactant micelies. Donbrow and Azaz (4,5) reported that the solubilization of phenolic compounds such as phenol, xylenol, etc. by nonionic surfactants was governed by the structure of the phenoiic compound, and the formation of hydrophobic complexes depressed the cloud point of surfactant. According to Cobby and Elworthy (6), the formation of hydrophobic complexes is caused by the binding of preservative to the EO-chain of surfactant molecule. In our present study, the solubilization of butylparaben (BP) being used as a preservative for foods, drugs, and cosmetics in the aqueous solution of various 297