THE DISTRIBUTION AND ACTIVITY OF BENZOIC ACID 213 Table V Fungistatic activities (as FC 50) against A. niger of benzoic acid in emulsified systems: at 25 ø and pH 4.2 , FC 50 (per cent aqueous phase) Phase ratio Concentration Concentration Aqueous phase Oil phase w: o of benzoic unbound and acid added unionized in aqueous phase Buffer only None 0.055 0.027 -- 9.1 • Brij 35 None 0.056 0.027 Liquid paraffin 2: 1 0.062 0.030 Liquid paraffin 1: 1 0.065 0.029 Arachis oil 2: 1 0.136 0.027 Arachis oil 1: 1 0.230 0.028 Isopropyl myristate 3:1 0.147 0.027 __ 20 • glycerin None 0.072 0.040 20 •o glycerin None 0.076 0.042 •.nd Liquid paraffin 1: 1 0.080 0.041 •.1% Brij 35 Arachis oil 2: 1 0.145 0.036 isoPropyl myristate 3: 1 0.152 0.037 These results suggest that the fungistatic activity of benzoic acid in an emulsified system depends on the amount free in the aqueous phase, and that the amount required to compensate for losses into oil phases can be calculated if the appropriate partition coefficient is known. Contrary to the results of Bean et al (4, 13, 14), the phase volume ratio does not seem to affect the activity, although it should be pointed out that a different organism, a different method and a different preservative have been used in the present study in addition the inclusion of surfactant molecules which concentrate at the oil-water interface would be expected to affect adsorption of microorganisms at the interface. ACKNOWLEDGEMENT This work has been supported by the New South Wales Pharmacy Research Trust. (Received.' 3rd October 1966) REFERENCES (1) Bolle, A. and Mirimanoff, A. J. Pharm. Pharmacol., 2 685 (1950). (2) Wedderburn, D. L. in Advances in Pharmaceutical Sciences, 1 195 (1964) (Academic Press, London).

214 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (3) Arkins, F. Mfg. Chem., 2t 51 (1950). (4) Bean, H. S., Heman-Ackah, S. M. and Thomas, J. J. Soc. Cosmetic Chemists, t6 15 (1965). (5) Garrett, E. R. and Woods, O. R. J. Am. Pharm. Assoc. Sci. Ed., 42 736 (1953). (6) Glasstone, S. Textbook of Physical Chemistry, 738 (1946) (Van Nostrand, New York). (7) Evans, W. P. and Dunbar, S. F. in Surface Activity and the Microbial Cell, S.C.I. Mono- graph No. 19, 169 (1965) (Society of Chemical Industry, London). (8) Winsley, B. E. and Walters, V. J. Pharm. Pharmacol., t7 225 (1965). (9) Hibbott, It. W. and Monks, J. J. Soc. Cosmetic Chemists, t2 2 (1961). (10) Albert, A. and Serjeant, E. P. Ionization Constants of Acids and Bases 80 (1962) (Methuen, London). (11) Mitchell, A. G. and Brown, K. J. Pharm. Pharmacol., t8 115 (1966). (12) Anderson, R. A. and Slade, A. H. Australian J. Pharm. Sci. Supp., 46 S53 (1965). (13) Bean, H. S., Richards, J.P. and Thomas, J. J. Boll. Chim. Farm., t01 339 (1962). (14) Bean, H. S. and Heman-Ackah, S. M. J. Pharm. Pharmacol., 16 58T (1964).