220 JOUR•NAL OF THE SOCIETY OF COSInETIC CHEMISTS TABLE VI /fey: -]- ---- growth after 24 hours (preservative inactive) -- no growth after 72 hours (preservative active) 0-1% 0.1% 0.1% 0.1% 0.1% 0.1% 0.1% 0.1% B.A.C. B.A.C. B.A.C. B.A.C. B.A.C. B.A.C. B.A.C. B.A.C. alone + + + + + + + 0-1% 0'2% 0.5% 0'75% 1-0% 1.5% 2.0% Tw. 80 Tw. 80 Tw. 80 Tw. 80 Tw. 80 Tw. 80 Tw. 80 __ Staph. a ........ albus __ __ Strep. a ........ boris _ -- B. coli a .... + + + + b ..... + + + -- Ps. a .... + + + + •o•'- escens b .... + + + + Gram / // // / Table VI shows that' A ratio of 5: 1 (Tween 80 to Benzalkonium chloride) is the highest at which the preservative remains active against all of the test organisms. The Gram-positive organisms are far more sensitive to benzalkonium chloride than the Gram-negatives, and the efficiency was not affected even at a ratio of 20 to 1. (Further experiments have shown that one part of Benzalkonium chloride is active against Gram-positive bacteria at ratios of up to 100 parts of Tween 80.) Effects of Nonionics of Different Structure on Preservatives The results given in Table I indicated differences between the various classes of nonionic surfactants with regard to their effect on preservatives. Although all reduced the efficiency of many preservatives, the degree of inactivation was not equal throughout. As it seemed likely that the key to solving the problem of preservative inactivation might lie in the structure of the nonionic surfactants, experiments were carried out to assess the differences between them. Two preservatives (Nipa 82121 and benzalkonium chloride) were used, and twenty-two nonionics, nine of which were non- surface-active. In these experiments the nonionics were incorporated in nutrient broth at 2 per cent together with the preservative. Nipa 82121 w. as tested at

PRESERVATION OF TOILET PREPARATIONS CONTAINING NONIONICS 221 0.15 per cent and benzalkonium chloride at 0.1 per cent. Three Gram- positive and three Gram-negative organisms were used and each culture was tested at six different strengths. As controls, all the organisms were grown simultaneously in broth containing 2 per cent of the nonionics but no preservatives. Tables VII and VIII show the results. TABLE VII Each Nonionic at 2% with Bripa 82121 at 0'15% Active Inactive Gram +ve Gram-Ve Grarn+Ve Gram .-ve Strength of culture. 1 2 3 4 5 6 2 3 415 6 2 3 4 5 6 213 4 5 6 I Nipe 82121 alone. Glycerine Sorbitol I Propylen e qlycol Tallow P. E.G. 200,400&60C P. E.G. 2OOO81OOOO. P.E.G. 400 Laurate' Nonex 64 & 99 CremophonE.L. Glyceryl monostearate Tween 20 H.I R-•6.7 H.L.B.15.6 Tween BO i H. LB.-'14 I -- Span 20 i H.L.B:B.6 I • I Adacel 83 H.[_B-3-7 I __ lubrol W. Tcxofor D I i I Sucrose esters.