TESTING DEODORANTS WITH CHLOROPHYLL AND DERIVATIVES 65 nished by the soil removed from skin in the perspiration. 3. A balance of base over acid in perspiration promotes growth and multiplication of cutaneous bacteria ,and, also, enhances the develop- ment of perspiratory odors. 4. Correlations of results of .chemical analyses with the findings in organoleptic tests of samples of perspiration before and after incuba- tion at 37øC. for twenty-four hours showed that increases in intensities of perspiratory odors were coinci- ,dent with increments in volatile base and volatile acids but the rises in concentrations of volatile bases in perspiration were greater than the concomitant increases in volatile acids. The resulting balance of base over acid results in the eleva- tion of the pH of perspiration to lev- els above 7.00. This increase in pH levels of perspiration is a uniformly characteristic, physico-chemical change associated with the produc- tion of malodorous metabolites of cutaneous bacteria. In a comprehensive program for tests or experimental studies of the comparative deodorant efficiencies of either tentative formulas or fin-- ished products, intelligently planned in-vitro methods of testing may con- tribute information of practical value in reference to (a) the com- parative efficiencies of the product under test as either a deodorizing agent or an inhibitor of odor devel- opment (Table 3), (b) the mode of action of the preparation, e.g., either by lethal or bacteriostatic actions upon cutaneous micro6rganisms (Table 3), or by chemical reactions with the sources of odors (Tables 3-A, 4, and 5), (c)the environ- mental conditions which may influ- ence the effectiveness of the prepara- tion either.as a deodorizing agent or as an inhibitor of the development of odors, e.g., variations in balances of base and acid in the medium in which sources of odors are dissolved or suspended and to which the prep- aration is added (Tables 3-A and 6), and (d) the molecular structures of the sources of odors, having varying qualitative characteristics, upon which the preparation under test is effective as a deodorant (pages 45 and 50). These potentialities of in-vitro methods of testing deodorants have been illustrated by citations of their applications to five series of experi- mental studies of chlorophyll and its derivatives. Results of these as- says have demonstrated that natu- ral chlorophyll and its water-soluble derivatives, viz., sodium-magnesium chlorophyllins and sodium-copper chlorophyllins, exhibited their max- imum efficiencies as deodorants un- der test conditions in which the odor- ous compounds in vapor phases are exposed to either the natural chloro- phyll or the combination of chloro- phyllins "a" and "b" in solid phases. In order to eradicate odors arising from sources soluble in water, it is essential that the chlorophyll deriva- tive be either water-soluble or dis- persible in colloidal form in the liq- uid to which it is added. Deodorant capacities of water- soluble chlorophyllins "a" and "b"

66 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS are dependent upon the base-acid balances of the solutions of the sources of the odors. The chloro- phyllins exhibit deodorant actions only in neutral or alkaline solutions. The range of base-acid balances which are optimum for deodorant effects of the chlorophyllins are in- dicated by levels of pH between 8.0 and 10.5. Even weakly acid solu- tions (pH = 5.70) inhibit the de6- dorizing actions of these derivatives of chlorophyll. A hydrion concen- tration equivalent to pH = 5.30 is critical for the deodorant actions of the chlorophyllins. Progressive reductions in deodorant efficiencies concomitant with rising hydrion concentrations are attributable to decreasing solubilities of the chloro- phyllins in acid solutions. Com- plete precipitation of sodium-copper chlorophyllins "a" and "b" is ef- fected by increasing the a6idities of their aqueous solutions to pH = 4.50. Water-soluble chlorophyllins "a" and "b" added to malodorous sam- ples of perspiration effect prompt eradications of the perspiratory odors. At the same time, these chlorophyll derivatives exhibit an- tibacterial actions. In one series of tests (Table 3), 0.100 per cent of the chlorophyllins effected a reduction of more than 99 per cent in the num- bers of viable bacteria in stale per- spiration. In addition to their deo- dorizing actions, the chlorophyllins, added to fresh samples of perspira- tion, inhibit the development of perspiratory odors under condi- tions of storage which are optimum for the production of obnoxious odors. The series of experiments which have been cited in the preceding par- agraphs exemplify the types of prob- lems to which in-vitro methods of testing may be adapted and concern- ing which the intelligent utilization of these procedures may yield basic information of practical value, par- ticularly in the formulation of deodorant preparations. However, limitations of in-vitro techniques necessitate the adoption of in-vivo methods for purposes of either evalu- ating the deodorant efficiency of the final product or in comparative studies of two or more preparations on the market. Three series of experiments have been included in this report with the objective of directing attention to some of these limitations of in-vitro methods. The first of these series of experiments (Charts IV and V) is representative of one category of problems to which in-vitro methods are not adaptable as the sole means of acquiring information adequate for the critical judgment of deodor- ants. Within the limits of the au- thor's knowledge, no in-vitro method has been developed and, in extensive trials, has been found to be a satis- factory substitute for actual use- tests of soaps or other types of d•- tergents as skin cleansers. This conviction based upon experiences over periods of approximately two decades in experimental studies of skin cleansers, was the reason for the adoption of tub baths in the se- ries of comparative tests of the deo-