EVALUATION OF ANTiPERSPIRANT ACTIVITY 763 The large black knob on the right front of each instrument encloses the moisture sensing cell (Fig. 11). It consists of a capillary U-tube containing two separate spiral electrodes. -L•'FTj _ co! ,LI 8R^TtOlXl . I, I The whole assembly is en- b ' co•r•½ ,' , / - LEFT _ • / /•, , _ RIGHT o lo 20 30 '40 50 •'• Figure 15. Results of a series of tests as outlined in Table 1: 13a is the control 13b is Test 1 13c is Test 2 and 13d is Test 3 (note changing slopes) capsulated in epoxy resin. The electrodes are activated with phosphoric acid which, when subjected to an electric current, is converted to the non- conducting phosphorus pentoxide by the electrolytic destruction of the water present. As a result, the conductivity of the cell is reduced essen- tially to zero. When the cell senses moisture, its conductivity will rise accordingly. The meter reads this conductivity and will balance when the input of moisture equals its destruction.

764 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 100 90 80 70 6O 5O 4O $0 20 lO Aver=ge Perspir=tion Depressions -A -B -C -D -E Prod. APlPl. C D o I hr. 4 hrs. Test Test Prod. Prod. Prod. I Appl. Ap•31. Appl. I 2 hrs. 3 hrs. Test Test Time, hours Figure 14. Graphic comparison of the test results obtained for five products, each tested on five subjects This type of sensor was specifically chosen because it records all of the moisture present in the stream. It is insensitive to relative humidity variables in the gas stream caused by temperature changes. The slight changes which may occur in the gas velocity due to small temperature changes are negligible. Finally, the electric signals representing changing moisture levels in the two gas streams are delivered to an x-y recorder (Fig. 12). This machine automatically plots the values received from each area being measured against one another. The simultaneous variations in perspira- tion rates represented by these values appear as a line pattern with a