26 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (5) Manowitz, M. in Developments in Industrial Microbiology III 265 (1962) (Plenum Press, New York)'. (6) Rigler, N. E. and Schimmel, J. in E. Sagarin, Ed. in Cosmetics, Science a•d Technology (1957) (Interscience Publishers Ltd., London). (7) Stokoe, W. N. Analyst 49 577 (1924). (8),Brown, A. R. in Trop. Deft. of Equip•nt and Materials I Chapter 5 (1946) (National Defence Research Comm., Washington, D.C.). (9) Reese, E. T., Cravetz, H. and Mandels, G. R. Farlowia 4 409 (1955). (10) Castell, C. H. and Garrard, E. H. Can. J. Res. 19C 106 (1941). (11) Janot, M. M. and Ruoss, L. Pharm. Acta. Helv. 30 8 (1955). (12) Hugo, W. B. and Beveridge, E.G. J. Appl. Bacteriol. 25 72 {1962). (13) Beerstether, E. in Petroleum Microbiology 336 {1954) (Elsevier Press, Amsterdam). (14) Strawinski, R. J. and Stone, R. W. Can. J. Microbiol. I 206 (1954). (15) Ladd, J. N. Nature 177 939 (1956). (16) Sawyer, C. N. and Ryekmart, D. W. J. Am. Water Works Assoc. 49 480 (1957). {17) Baker, J. H. J. Soc. Cosmetic Chemists 10 133 0959). {!8) Bayliss, M. J. Bacterio1:51 489 {1936). (19) Barr, M. and Tice, L. F. J. Am. Pharm. Assoc. Sci. Ed. 46 442 (1957). (20) Bolle, A. and Mirrimanoff, A. J. Pharm. Pharmacol. 2 685 {1950). (21) Kostenbauder, H. B. Am. Perfumer Aromat. 75 28 (1960). {22) Mulley, B. A. and Metcalf, A.D. J. Pharm. Pharmacol. 8 774 {1956). (23) Dyer, D. L. Soap Chem. Specialties :54 53 139 (1958). (24) Alexander, A. E. and Tomlinson, A. J. H. in Surface Chemistry 317 {1949) {Butterworths, London). Bean, H. S. and Berry, H. J. Pharm. Pharmacol. :5 639 {1951). Bean, H. S. and Berry, H. J. Pharm. Pharmacol. 5 632 {1953). Wolffi•Iigel, G. and yon Knorre, G. Mitt. Kaiserl. Gesundheitsamt I 352 (1881). Clark, W. C. Am. J. Pharm. III 228 {1939). Gershenfeld, L. and Brillhart, R. E. Am. J. Pharm. III 430 (1939). Spalton, L. M. in Pharmaceutical emulsions and emuZsifying agents, 2rid Ed., 98 (1953) {Morgan Brothers, London). {31) Arkins, F. Mfg. Chemist 21 51 (1950). {32) Hibbott, H. W. and Monks, J. J. Soc. Cosmetic Chemists 12 2 {1961). (33) Pivnick, H. and Fotopoulos, K. Lubrication Eng. 1:5 151 (1957). {34) Carlson, V. and Bennett, E. O. Lubrication Eng. 16 572 {1960). (35) Taylor, H. S. in A treatise on Physical Chemistry I 363 (1924) (MacMillan & Co. Ltd., London). (36) Bean, H. S., Richards, J.P. and Thomas, J. Boll. Chim. Farm. 101 339 {1962). (37) Bean, H. S. and Heman-Ackah, S. M. Proc. oe3rd Intern. Congr. Pharmaceutical Sciences, Miinster 517 (1964) (Govi-Verlag, Frankfurt/Main). {38) Bean, H. S. and Heman-Ackah, S. M. J. Pharm. Pharmacol. 16 suppl. 58T (1964). DISCUSSION MR. S. A. H•LL: One of the most interesting points brought out in these experi- ments of the simple two-phase systems is that the interface, although the least important of the factors affecting the preservative activity, does have statistically a highly significant effect. I agree that, in the emulsion systems which you will eventually be investigating, other factors affecting preservative activity will certainly arise. I would like to know if, on the basis of the results gained so far, you would anticipate that the interface could become more important than either the phase• volume ratio or the partition coefficient of the preservative owing to the very large interfacial area in emulsions. DR. H. S. BEAN : In emulsified systems the oil/water ratio will control the con- centration of preservatives in the aqueo'us phase and will always be an important (25) (26) (27) (28) (29) ß '(30)

THE ACTIVITY OF ANTIBACTERIALS IN TWO-PHASE SYSTEMS 27 factor. Phenol or preservative molecules are absorbed at the interface together with bacteria, and also emulgent particles, otherwise no emulsion would be obtained. Exactly what will happen to the activity is uncertain especially as some of the surface active molecules will be absorbed on the bacterial surface. At the bacteria/ water interface there will be a build up of micelies and some of the preservative may go into a solution in the interior of the micelies thereby changing its availability to the micro-organism. At the moment it is very difficult to see how all these factors are going to interact. DR. E. E. BoEaM: In page 10 there is the statement "it has long been known that phenols dissolved in oils and fats possess no antimicrobial activity except when the oil is in contact with the water". This statement is not in agreement with the experimental results obtained by Sabalitschka and Priem (89) where it was shown that a 10•o solution of phenol in oil, in the absence of water, kills Staphylococci within 7 hr. On mixing with g •o water the same organism was killed within 50 min. Under otherwise similar conditions a solution of g • phenol in water killed this. organism within 5 min. In fact, phenol dissolved in oil in the absence of water was about gO times less effective, and in the presence of traces of water about 10 times less effective than an aqueous solution of phenol. Resorcinol in oil, under similar test conditions, appeared to be about 10 times weaker than an aqueous solution of the same concentration, but after mixing with g •o water was twice as strong as an aqueous solution of the same concentration. The authors explained this in terms of the different distribution of both phenols between the oil and water. TaE L•CTUR•R: Our observations are in no way different from those of Sabalitschka the difference lies in the interpretation. Prof. Sabalitschka grew his organisms on agar and they were not dried organisms. There was a proportion of water there and the preservative in the oil was partitioning into this small quantity of water. When he added water to g •o the activity increased, which is absolutely compatible with• the statement made in our paper. He reduced the phase volume ratio, and therefore. increased the preservation concentration in the aqueous phase indicating that he . was using a system in which the partition coefficient was high. DR. N. D. HARRIS: It seems to me that one of the real problems in this discussion is whether one can decide what the antibacterial activity of materials is in oil? Ta• Lv, CTURv, R: Yes, of course, this is one of the difficult things, which no one has solved satisfactorily so far. I think Professor Bullock was getting very near it- but he had to use a factor to allow for a very high mortality in his organic solvents. MR. R. SMART: We have infected arachis oil by spraying a water suspension of' spores or cells into air, and "sampling" volumes of the air by a slit-sampler. If the. usual nutrient agar plate is replaced by a plate containing a membrane filter moistened_ with oil, the cells adhere to the oil layer. The cells can be taken into a volume of oil by inverting the membrane in a filter holder and washing with more oil. To estimate the number of viable cells on a membrane filter the latter is placed in the filter holder the right way up, washed with about 10 ml polyethylene glycol 800 10 • v/v solution in water and cultured in the usual way. The number of cells impinging on the membrane can be estimated in the slit sampler by counting the colonies produced on a nutrient agar plate in the same area as the membrane filter. (39) Sabalitschka, T. and Priem, A. Fette Seifen Anstrichrnittel 46 277 (1939). 4