230 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS pyridinium chloride" may be either a pure Cx• derivative or, as with com- mercial grades of sodium lauryl sulphate, a mixture of homologues only part of which is Cx•. Likewise it is widely believed that cetnmide is synonymous with cetyltrimethylammonium bromide (see, e.g., cetrimide is not and has never been cetyltrimethylammonium bromide, but simply contained cetyltrimethylammonium bromide as one component, as in the case of a number of products described as "cetyltrimethylammonium bromide." Traditional methods of analysis cannot readily establish the composition or concentration of a quaternary ammonium compound, and new methods of analysis have had to be devised to resolve these difficulties.• •)UARTERNARY AMMONIUM COMPOUND FORMULATIONS Typical formulations based on quaternary ammonium compounds have been reviewed previously. TM The present discussion will therefore be limited to uses of major importance and in particular to current trends. / Bactericidal Use A number of products covering widely different consumer application's are now• available which utilise the bactericidal properties of quaternmy ammonium compounds. These include antiperspirants and deodorants, barrier creams, antiseptic creams, dandruff remedies, baby creams, lotions and powders, after-shave lotions, together with various pharmaceuticals such as cough syrups and lozenges, oral preparations of antibiotics, and, of course, antiseptic fluids. Of interest in view of the introduction of by-laws governing the conduct of hairdressing establishments is the appearance of a quaternary ammonium compound based disinfectant which has been designed especially for use in hairdressing saloons and b•auty parlours. •4,•5 The vast majority of the above type of products contain as active bacteri- cide either cetrimide, benzalkonium chloride or cetylpyridinium chloride. Permanent Waving and other Hair Treatments It has become widespread practice to use a quaternary ammonium compound preparation at one or another stage of permanent waving. The quaternary ammonium compound may be included with thioglycollate in waving lotions or creams, with the neutraliser, or used after the waving process as a conditioner or as a setting lotion. The last two types of product are more frequently used after normal shampooing. The addition of quaternary ammonium compounds to peroxide bleaches in salon practice is popular, and Hudnut •6 have recently claimed the prepara- tion of acid peroxide bleaches containing quaternary ammonium compounds. Shampoos based on, or containing minor proportions of quaternary

CATIONIC SURFACE-ACTIVE AGENTS 231 ammonium compounds continue to attract interest. For example, L'Oreal •? have claimed shampoo compositions containing cationic (c. 10 per cent), nonionic detergent (c. 2 per cent), carboxymethyl cellulose (1 per cent) and lactic acid (5 per cent). It would appear, however, that the preferred technique is to use a cationic as a separate treatment, perhaps largely because the cationics cannot compete economically with anionics as ordinary detergents. In closing, a few remarks may be made concerning formulation of a new quaternary ammonium compound based product. This is simple so long as the quaternary ammonium compounds are not expected to behave like anionics. Except where common sense and experience guide, one should not be put off by the numerous statements in the literature about incompatibili- ties the latter are sometimes most advantageous TM and several compositions containing these incompatibilities have been mentioned in the literature. For example one patent • claims the employment of the reaction product of equimolecular quantities of anionics and cationics in the preparation of ointments and skin creams. A further example has already been quoted." Viscosity can be increased in quaternary ammonium compound solutions or creams by the addition of gums, cellulose ethers, non-ionics, fatty alcohols, lipids, or by simple inorganic salts. Clear, watery solutions of some quarter- nary ammonium compounds may be gelled by the addition o• a suitable salt. This effect is due to the normal salting-out caused by the electrolyte together with the conversion of part or whole of the quaternary ammonium compound to a new salt. All other formulation problems are of the type applicable to all cosmetic products. Acknowledgement The author thanks the directors of Milton Antiseptic Ltd. for permission to publish this paper. REFERENCES Lincoln, P. A., g/Ianufacturing Chemist, 27, 353 (1956). Rohm and Haas Company, U.S.A., Technical Bulletin. Lawrence, C. A., Soap, _Perfumery and Cosmetics, 27, 369 (1954). Lincoln, P. A., British Patent 735,631. Sinnova, French Patent, 1,000,869. Valko, E. I., and Dubois, A. S., J. l•act., 47, 15 (1944). Shelton, R. S., Van Campen, M. G., Tilford, C. H., Lang, I-t. C., l•isonger, L., I3andelin, F. ]., and Rubenkoenig, H. L., J. •lmer. Chem. Soc., 68,753 (1946). Valko, E. I., and Dubois, A. S., J. •act., 50, 481 (1945). Celia, J. A., Harriman, L. A., Eggenberger, D. lXl., and Ilarwood, H. J., J. •lmer. Chem. Soc., 77, 4264 (1955). Hugo, W. B., J. Pharm. Pharmacol., 9, 145 (1957). Lincoln, P. A., _Pharmaceutical Jnl., 177, 1956, 251.