JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ' Bergmann and Stather. Z. physiol. Chem., 1926, 152, 189. •0 Nicolet. f. Amer. Chem. Soc., 1931, 55, 3066 1932, 54, 1998 f. Biol. Chem., 1932, 95, 389. n SchSberl and Weisher. Annalert, 1933, 507, 111 Sch6berl and ]•ambacher, ibid., 1939, 538, 84. •: Stoves. Trans. Farad. Sot., 1942, 35, 254. •3 Stoves. f. Soc. Dyers and Col., 1947, 63, 65. •4 Horn, Jones and. Ringel. f. Biol. Chern., 1941, 138, 141. is Speakman and •rhewell. f. Soc. Dyers and Col., 1936, 52 380. x• Nicolet and Shinn., .}'. Biol..Chem., 1941, 140, 685 f. Arner. Chern. S•c., 1941, 63. 2284. •7 Phillips and Cuthbertsor,, Biochem. j., 1945, 39, 7. xs Pruton and Clarke. f. 2•iol. Chef,., 1934, 106, 667. "Clarke. J. Biol. Chem., 1932, 97, 235. ,a Stoves, Trans, Farad. Soc., 1942, 38, 26t. • Phillips. "Fibrous Proteins" Sym- posium, 1946, 39. '• Stoves. Perfumery and .Essential Oil Record, 1952, 43, 232. '• USP., 2,201,929. e• Morelle. Soap, Perfumery d• Cos merits, 1952, 25, 828. •s USP. 2,577,710 2,577,711. '0 Freund. Australasian J. Pharmacy, 1951, 32, 944. aOMorelle. La Parfumerie Moderne, 1950, 51, 66 1951, 64. '• Austrian Pat. 166,240. a• •eilingotter. Seifen-Ok-Fette- •chse. 1950, as Hungarian Pat. 139,973. . aa Can. Pat. 465,446 - '•.f. USP, as French Pat. 844,529. *s BP• 484,•67. 1951, 75. •s B.P. 636,181[ •* Stoves. Nature, 1946, 157, 230. '• Stoves. Research, 1951, 4, 485. ß •l Patterson et al. J. Res. Nat. Bur. Stand., 1941, 27, 89.

STABILITY TESTING OF HAIR • " -' By G..S. KASS, B.S.* IN establishing laboratory methods ili:?.for testing the stability of cosmetic ?:i'products, four types of product ?.:•?Stability must be evaluated. These are chemical, physical, bacteriologi- :•j}! i'-.:: cal, and what can perhaps be referred :':•?:i to as functional stability. 5??' Chemical stability is the absence •:.:!•!'i:.of any chemical reaction 'in the i?!'i:i':packaged product, especially where so-called active ingredients are pre- sent. Chemical deterioration or •(•i:': changes in the product often bring i'½ i:}i about some change in the appearance :i'i}'..of the product as well, and may be :')(:::::detected visually. But very fre- ?::quently chemical changes are not accompanied by visible physical' changes, and chemical analysis must •.::' be resorted to in order to detect such a change. Typical examples of chemical instability where the ap- pearance of the product is not usually affected are (a) a drop in the thiogly- collate concentration of cold wave solutions, due to oxidation and usually detected by iodimetric titra- tion' and (b) the decomposition of solutions of hydrogen peroxide, which is usually detected by a permanganate titration. * Helene Curtis Industries, Inc., Chicago 39, Illinois. Paper presented before the Chicago Section, November 1951. PREPARATIONS .. The physical stability of a product may be adversely affected by such phenomena .as emulsion separation, creaming, pigment settling, clouding or turbidity in clear liquids, discolor- ation, and precipitation or crystallisa- tion in liquid products. Both chemical 'and physical changes may be interrelated and a . chemical change can and often does cause a change in the appearance of the product. Odour changes can also be included in this group-because they can easily be detected by an educated nose. Bacteriological stability is a third requirement. The ability of micro- organisms to ruin a product is well known, and a product which is not properly protected from the develop- ment of micro-organisms usually ends up in the "returned. goods depart- ment" of the manufacturer. A fourth and often overlooked kind of product deterioration is what I like to refer to as the functional instability of a product. No product can enjoy repeat sales unless it does the job it was designed to do. Appearance, odour and packaging will not sell a product that does not measure-up to the performance claims on the label and in its adver- tisements. In many instances, if a product does not function properly 181