370 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (73) (74) (75) (76) (77) (78) (79) (80) (81) (82) (83) (84) j. H. Bradbury and J. D. Leeder, Keratin fibres. IV. Structure of cuticle, Aust. J. Biol. Sci., 23, 843-854 (1970). J. H. Bradbury and J. D. Leeder, Keratin fibres. VI. Mechanism of the Allw/3rden reaction, Aust. J. Biol. Sci., 25, 133-138 (1972). J. D. Leeder and J. H. Bradbury, Effects of shrinkproofing and other chemical treatments on the epicuticle of wool, Text. Res. J., 41, 215-218 (1971). j. B. Speakman and A. C. Goodings, Chlorination ofwool,J. Text. Inst., 17, T607-614 (1926). J. D. Leeder and J. H. Bradbury, The discontinuous nature of epicuticle on the surface of keratin fibers, Text. Res..]., 41, 563-568 (1971). G.J. Schuringa, T. Konings, and A. J. Ult•e, Jr., Osmotic active substances of the Allw/3rden reaction, Text. Res. J., 23, 645-646 (1953). H. Russina, Chlorination and determination of wool, Mell. Textilber., 12, 404-406 (1931). R. Bentham, C. B. Stevens, and C. S. Whewell, Some observations on the degradation of wool by hypochlorites with special reference to the action of hypochlorites on chemically modified wool, Proc. Intl. Wool Text. Res. Conf., Aust., C, 277-285 (1955). K. Baird, P. Nardon, and R. A. Foulds, A laboratory study of dry chlorination of wool at atmo- spheric pressure. II. Evaluation of treated wool,.]. $oc. Dyers Colour., 84, 29-39 (1968). W. H. Houff, C. J. Wells, and R. H. Beaumont, Chemical damage in wool. III. Effects of aqueous chlorine, Text. Res. J., 27, 961-965 (1957). H. P. Lundgren, Some observations on the oxidative degradation of the protein chains of wool, J. Text. Inst., 51, T806-816 (1960). I. C. Watt and R. Morris, The absorption of chlorine by wool, Text. Res. J., 34, 701-705 (1964).

j. Soc. Cosmet. Chem., 38, 371-384 (November/December 1987) The chlorine-hair interaction. II. Effect of chlorination at varied pH levels on hair properties N. B. FAIR and B. S. GUPTA, University of Missouri-Columbia, Columbia, MO 65211 (N.B.F.), and North Carolina State University, Raleigh, NC 27695-8301 (B.S.G.). Received April 23, 1987. Synopsis The results of a study of the effect of chlorination at varied pH on selected physical properties of human hair fibers are presented. The hair was treated in 10 ppm chlorine solutions at either pH 2, 7, or 10 for durations of up to 30 hours. Acid chlorination produced the greatest and most rapid change in interfiber friction, surface morphology, weight loss, and the greatest reduction in the force required to extend wet fibers 20%. Chlorination at pH 7 produced a more gradual change in these properties. Alkaline chlorina- tion produced little significant change in the properties examined. INTRODUCTION A review of the literature (1) has provided an insight into the mechanisms by which chlorine affects wool and the general consequences of the reaction. It has also provided specific information on the changes that take place in some of the properties of wool during commercial shrinkproofing treatments involving this reagent. Although both wool and human hair are keratin fibers, when analyzing the effect of chlorine on the latter, in light of the published work on the former, it is important to consider the differences which exist between the two fibers. A wool fiber is generally smaller in diameter (10-30 Ixm) and is covered by cuticle cells which overlap singly. A human head hair is relatively thicker (60- 100 Ixm in diameter) and is covered by 6- 10 layers of overlapping cuticular cells. Additionally, human hair has a considerably higher cys- tine content than wool. Also important to consider are the differences that exist between the treatment condi- tions to which the two fibers are exposed, conditions of shrinkproofing in the case of wool and those of swimming in the case of hair. In shrinkproofing wool, the chlorine concentration is generally 2-4 percent (based on the weight of wool), the pH of the treatment solution is below 6, and reaction times are usually short (of the order of minutes) (2,3). Under these conditions, chlorination could be expected to be restricted essentially to the surface, with little effect expected on the cortex (4). On the other hand, in swimming pools, in which hair is exposed to chlorine, the conditions are much milder. The pH level of the water generally lies between 6 and 8, and the available 371