NIPA-ESTER COMBINATIONS AS PRESERVATIVES AND ANTISEPTICS 35 solution (the conditions under which all our tests were carried out) 0.2 per cent Nipagin M was incapable ot killing the organism completely within twenty-four hours, whereas the ester combinations had a bactericidal effect well within that time. 0-03 per cent combination "64" (an example of an ester combination prepared by method 1) killed the more resistant of the two strains we used (N.C.T.C. Z248) within 30-60 minutes, and a 0.1 per cent solution of Combination "82121" and a 0.075 per cent solution of Combination "82123" (prepared in accordance with method 3) killed it within 5-15 minutes. Further tests were carried out in the same way with a number of organisms whose exclusion from cosmetic products is of the utmost impor- tance. Table II shows the results obtained in tests against two strains of Staphylococcus pyogenes (aureus) in which several concentrations of phenol are included for comparison. TABLE II Stap h y lococcus Stap h y loc occ u s pyogenes (aureus) pyogenes {aureus) N.C.T.C. No. 7447 N.C.T.C. No. 7972 Growth after: Growth after: 5' 15 •30' 1 2 424hrs. 5' 15' 30' 1 2 424hrs. (1) 0.5% phenol .... q- q- q- 4 q- q- q- q- q- q- q- q- -- (2) 0.75% ...... + q- + + -- + (S) 1.0% .. q- - -- q- q- (4) C.24% m•ihyl •'-hy- droxybenzoate .. q- • + q- + + -- + q- q- q- + -- -- (S) 0.04% propyl p-hy- droxybenzoate .. 4- 4- 4- q- q- q- -- q- + + q- + q- {6) 0-03% Nipa-ester com- bination64 .... q- q- q- • ..... + q- q- + q- (7) 0.075% Nipa-ester com- bination 82121 .. q- -½ q- q -- q- q- q- q- -- {8) 0.1% Nipa-ester com- bination82121 .. q- q- q- -- q- q- q- -- (9) 0.14% Nipa-ester bination 82121 .. q- q- - - q- q- (10) 0-075% Nip•-ester com- bination 82123 q- q- q- -- q- q- q- -- (11) 0.1% Nipaseptq-0.03•o Nipa-ester combina- tion 64 q- (12) 0.12% Nipasep•-0.03'ø)o Nipa-ester combina- tion 64 .... q- -- q- q- Tests against Bacterium colt, Proteus vulgaris and Pseudomonas pyocyanea were carried out in the same way, and the results are tabulated in Tables III and IV. In the case of Pseudomonas pyocyanea we have included the well-known antipyocyanea compound "Phenoxetol BPC" in our tests.

36 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE III Bacterium coli Proteus wdgaris Culture Clausen Iq.C.T.C. No. 4175 Growth after: Growth after: 30' 1 2 4 24hrs. 30' 1 2 4 24hrs. (1) 0.5% phenol .... + + + + + + + + + -- (2) 0-75% ...... + + -- -- -- + + -- -- -- (3) 1.o% ...... (4) 0.24% m•hyl p-•drox•' benzoate (5) 0.04% propyl p-•drox•'- q- q- q- q- -- q- q- q- q- -- benzoate .... + + + + + + + + + -- (6) 0.2% Nipasept .... -- -- + + -- -- -- (7) 0.075 % Nipa-ester combina- tion 82121 .... + + + q- + + + -- -- -- (8) 0.1% Nipa-ester combina- tion 82121 .... q- q- q- q- -- q- -- -- (9) 0.14ø./o Nipa-ester combina- tion 82121 ...... (10) 0.075 % Nipa-ester combina- tion 82123 .... q- q- q- q- .... TABLE IV Ps. pyocyanea Ps. pyocyanea (from Whipps Cross Iq.C.T.C. No. 7244 Hospital) Growth after ß Growth after: 30' 1 2 4 24hrs. 30' 1 2 4 24hrs (1) 0.5% phenol .... q- q- q- -½ -- q- q- q- q- -- (2) 0-75% ...... + + -- -- -- + + -- (3) 1.o% .... - ....... (4) 1.0% ph•oxetol .. q- q- q- + -- q- q- q- -- -- (s) 2.0% ........... (6) 0.24% methyl p-/•droxf benzoate (7) 0.04% propyl p-•drox•'- + q- q- + -- q- q- + q- -- benzoate .... + (8) 0'2% Nipasept .... + .... + -- -- -- (9) 0.1% Nipa-ester combina- tion 82121 .... + + + + -- + + + + + (10) 0.14% Nipa-ester combina- tion 82121 .... -- ..... A further test of a different kind was carried out to find the effect of single esters and of some ester combinations on the rate of fermentation of a 2 per cent glucose solution by bakers' yeast. Sterile solutions of the esters or their combinations in :2 per cent glucose were poured into sterile urometer tubes which were each inoculated with 0.5 gram bakers' yeast and incubated for two hours at 37 ø C. Table V shows the relative amounts of fermentation which had taken place during this time (as measured by