762 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 12. x-y recorder rest. In this way, the variation in perspiration will cause the x-y re- corder to trace a sloped pattern on the graph. It has been found that when a subject lies still in the warm atmos- phere he may be lulled to sleep by the hypnotic drone of the equip- ment. When asleep, his perspiration can become quite erratic. An actual alternating pulse of one axilla followed by the other has been ob- served. The moisture monitors (Fig. 10) are placed side by side so that their meters may be viewed simultaneously. The two flow meters on the top right of each instrument measure the total flow of gas and the quantity that is sampled for moisture content. The system is calibrated to read in •1/1 (parts per million) of moisture u-'hen the sample flow is set for 10 ml/min. Since the measurements required are all relative, the exactness of this calibration is unimportant. However, the gas flows should not change during a test. Several scales may be selected by the attenuator switch on the left front of each instrument. Its position will depend on the relative output of perspiration of the subject under test.

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.