90 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS As mentioned before, the comparatively high degree of acidity which is generated by the hydrolysis of the aluminum salts poses a problem in for- mulation. If left unchecked, such acidity might have an irritant effect on the skin either directly or in repeated use, also a destructive effect on cer- tain fabrics of cellulose character or provenance, notably those of linen, cotton and viscose rayon silk, wool, nylon and acetate rayon fabrics appear to be more resistant. Prolonged or repeated contact of the fabric with the strongly acid antiperspirant preparation may cause gradual rotting, max- imum damage being produced at the higher temperatures of ironing to which the fabric may be subjected directly, i.e., without preceding launder- ing. Thus, if in the course of being worn, a linen garment picks up some improperly formulated antiperspirant from the axilla, and if it is then ironed without having been laundered, the acidity of this residue on the fabric may be activated to such an extent that irreparable damage will re- suit however, if this acidity is controlled by correct formulation, damage to the garment will be avoided. Considerable light upon the several fac- tors involved in this matter has been thrown by Bien (16) who also sug- gested a method of obtaining advance information as to the likelihood of any destructive action of antiperspirants on fabrics. The significance of this problem has been recognized early as evidenced by the fact that the literature, and particularly the patent literature, de- scribes a considerable number of presumably successful attempts to over- come the difficulty. The pertinent formulations may be divided into two categories, viz., those which call for the addition of inhibiting or "buffering" agents intended to reduce the high acidity of the hydrolyzing metal salts, and those which specify metal compounds developing a lower degree of acidity, i.e., without the aid of added buffers or inhibitors. In the former category, an earlier patent granted to Tare (17) provides for the addition of borax to a. rather concentrated solution of aluminum chloride and alum. Teller (18) claims that the destructive effect on fabrics of the acidity of the astringent salts may be counteracted by the addition of basic alu- minum formate. Several patents issued to Montenier (19) cover a number of protective compositions. By way of illustration, one of them provides for the com- bination with aluminum chloride of certain organic compounds charac- eR' terized broadly by the formula R--CO--N R" in which R may be an alkyl, cycloalkyl, aralkyl, aryl or one of the corresponding oxyradi'cals, while R' and R" may be hydrogen, alkyl, cycloalkyl, aralkyl or aryl groups. Examples of the inhibitory substances are acetamide, urethane and urea. Montenier's other patents specify the use of succinimide, pyrazol and of other imides and nitriles to counteract the acidity of aluminum chloride.

ASPECTS OF ANTIPERSPIRANTS AND DEODORANTS 91 A patent granted to Wallace and Hand (20) (later invalidated) covers the use of aliphatic amides and amino acids with at least one intact, reactive amino group as inhibitors of fabric corrosion and skin irritation. Perhaps the most important of these inhibitors is carbamide or urea. With respect to the protection of fabrics at higher temperatures, such as those of ironing, it is probable that the capacity of urea to liberate ammonia under these conditions plays a role in the neutralization of heat-activated acidity. Klarmann and Gates (21) obtained a patent which specifies the addition or formation in xilu of certain originally insoluble metal oxides and hydrox- ides, such as those of magnesium, zinc, also aluminum, etc. The hydrol- ysis of the astringent metal salt produces sufficient acidity to dissolve the water-insoluble oxides or hydroxides. Following are several patents which specify the use of astringent salts of the second category, i.e., those which are claimed not to develop any damaging acidity, and not to require any special inhibitory additions. The patent granted to Richardson and Russell (22) refers to the use of certain aluminum phosphates, such as the ortho- and the pyrophosphates. Aluminum chlorohydrate, also known as aluminum chlorhydroxide com- plex, is the subject of a patent issued to Anderson (23) recently, this patent has been declared invalid. In a patent granted to Grote (24, 25), dichloro aluminum aminoacetate hydrate is described as an innocuous agent suitable for antiperspirant for- mulation with water or with certain organic solvents. Govett and Alm- quist (26) describe in their patenrta double complex compound, viz., calcium aluminum basic chloride, said to be free from any deleterious action on fabrics. Aluminum sulfamate is the subject of two patents granted to Apperson and Richardson (27). While one patent covers the use of aluminum sul- famate in various antiperspirant formulations (solutions, emulsions, creams, etc.), the other deals with additives employed to prevent fabric discoloration by contact with preparations containing aluminum sulfamate. ANTIBACTERIAL AND DEODORANT ACTION OF ANTIPERSPIRANTS It has been mentioned that antiperspirant preparations formulated with metal salts which develop an acid reaction are also deodorant in action to the extent that this depends upon the control of odor-forming skin bac- teria, the question arises as to the origin of such control. That the bacteria which are present on the skin are sensitive to acidity hag been known for a long time. It may be mentioned in passing that the so-called "acid mantle" of the skin is being credited with contributing materially to the control of the hazard of skin infection, through the mecha- nism of autogenous disinfection, a hypothesis advanced originally by Marchionini and his associates (28, 29). This hypothesis did not always