270 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISq'• salivary sediment once again. If there is complete recovery of the original pH differential, the test chemical has not been retained on the sediment. If recovery does not occur, the chemical has a desirable substantive effect. Figure 4. Figure 5. Figure 4 shows a photograph of the electrodes. One glass electrode is covered with a nylon thimble to hold the sediment, and another measures the pH of the surrounding solution. Figure 5 shows three of the cells in position in the water bath that is used for maintaining a constant tempera- ture of 37 ø. The complete equipment is shown by Fig. 6. A Minneapolis- Honeywell strip chart recorder is the uppermost instrument. Next belo• is an automatic switch for selecting circuits in succession from each of the six electrodes. Below this is the water bath with the cells in position and finally, at the bottom is a Beckman Model R pH meter. The use of this equipment permits testing three compounds simultaneously. Information on the active compounds among ethers, esters, alcohols, or phenols was presented recently (10). The next largest group of sub- stances were found to be amines, the results with which will be presented here. There was a total of 186 amines that contained ether, ester, alcohol, or phenol but no other groupings that might be active such as aldehydes, TABLE 1--II•IHIBITORY AMII•ES TESTED llq 10 PER CE•T PROPYLEI•IE GLYCOL (REcovERY LESS T•A• 30 PER CE•T) Cornpound Concn. o-Aminobicyclohexyl Gentian violet .... 2,4,6-Tri (dibu tyl-aminomethyl) phenol 4-Ethyl 1-isobutvl octyl diethanolamine 1,B-Hydroxyethyl 2 58 heptadecenyl imidazoline o-Anilinophenol 1,B-Hydroxyethyl 2-heptadecyl imidazoline 1.0 0.1 s/10 s/2 1.0 oo. s/2

ENZYME INHIBITORS FOR DENTIFRICES 271 ketones, organic acids, amides, halo- gen, nitro, sulfur, or inorganic sub- stances. Thirty-eight of these amines were tested in 10 per cent propylene glycol. These are considered separately because it has been found that this solvent sometimes enhances the action of a chemical, either by a true synergistic action or by increasing the concentra- tion at test. There were seven sub- stances of this group showing re- coveries less than 30 per cent as shown by Table 1. One of these substances is a high molecular weight amine, another a disinfectant, two are phenols as well as amine derivatives, two are irnid- azoline derivatives, and one is a ter- tiary amine. There is little to suggest that there is any common grouping among these compounds. The remaining 148 compounds were dissolved in water for test. It was observed that inhibition often occurred among ethylene diamine derivatives or ring structures which might be formed from ethylene diamine, with Figure 6. nitrogen in the 1,4 positions, Table 2. These included substituted ethylene diamines, the glyoxalidine or imidazoline ring, and the piperazine ring. There were just four active ethylene diamine derivatives, but only a few have been tried. There was one imidazoline compound active from the three that were tried. Twenty piperazines have been studied, ten of which were active. Activity is possessed by piperazines having an alkyl group of 7 to 12 carbon atoms linked to one nitrogen and no substituent larger than a methyl on the other nitrogen. There were also active phenyl derivatives with one to three phenyl rings present either singly or in one or more con- densed rings. As with the other types, activity is apt to occur only when one nitrogen has a free hydrogen or methyl group, and when there are one or more alkyl or aryl groups of 6 to 18 carbon atoms linked to one of the nitro- gen atoms. In addition, 111 other arnines were tested. Table 3 shows the names of compounds which permitted recoveries of less than 40 per cent. Both do-