366 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS At/A :o 1.0 0.6 0.2 2 6 •0 ,/Time (min) Figure 3. Effect of dyeing temperature on the substantivity of lawsone. x, 15 ø (0.429) i,, 30 ø (0.649) O, 40 ø (0.752) O, 50øC (0.763). A•o values are shown in parenthesis. Figure 3 gave a slope of 0.116 min- •/2. Substitution in Eq. 1, assuming a fiber diameter of 20 p•m, yields a diffusion coefficient of 9 x 10-•1 cm 2 sec-1, in good agreement with those observed by Forestier. The situation is not as simple as suggested by Figure 3. Felts were dried after extraction and examined with the tintometer and the colorimeter. Three general changes were

HENNA AND LAWSONE SORPTION BY WOOL 367 Table IV Colors Remaining on Felts Dyed With Lawsone, After Extraction Tintometer Dyeing Dyeing Matching Series Colorimeter Time Temp pH (min.) (øC) Red Yellow Blue L a b 4.5 30 30 8.6 10.0 2.0 36.4 19.6 18.0 4.5 30 50 8.9 10.0 2.5 34.8 19.6 17.7 4.5 60 30 8.1 10.1 2.0 35.5 19.3 17.7 3.0 30 30 8.4 9.4 2.2 36.8 21.0 18.5 7.0 30 30 1.7 1.6 0 65.8 5.9 17.1 detected from felts freshly dyed with lawsone, in all samples and by both techniques. These were a decrease in the red component, a change in the predominant color from red to yellow, and a considerable increase in color depth. Some examples are shown in Table IV. The differences increased with dyeing time and dyeing temperature, sug- gesting that the changes in color were based on a chemical reaction. It is also evident that the products have a different color from the reactants and are more substantive to keratin. Forestier (1) observed that lawsone was more difficult to remove from hair eight months after dyeing than two days after dyeing, but did not comment on any change in color. His observation is complementary to our own and suggests that a slow reaction occurs, either producing a new compound which is more substantive to hair than law- sone or changing the mode of attachment to hair and thereby increasing the strength of the interaction. Forestier (1) suggested fixation of free -SH or -NH 2 in keratin to the 3-carbon in lawsone, to give complexes of the type shown in (II). The three primary colors of extracted felts decreased on changing the pH at which the dyeing process was carried out from 4.5 to 7.0. It therefore appears that the acid conditions employed when using henna are necessary to increase the proportion of the substantive reaction product formed on the hair but have no influence on the reactant, lawsone. Similar results were obtained with henna. In general, color depth was increased after extraction and also increased with dyeing time and dyeing temperature, but decreased with increasing pH, thus complying with the scheme outlined above. However, the complete set of results could not be fitted into any simple pattern, due probably to the intricate chemical composition of henna. REFERENCES (1) J.P. Forestier, Henn& Absorption de la lawsone par le cheveu, Int. J. Cos. Sci., 4, 153-174 (1982). (2) E. M. Holmes, Henna, Pharm. J., 112, 437-439 (1924). (3) H. E. Cox, Hair dyes. I. The chemistry and analysis of henna, Analyst, 63, 397-404 (1938). (4) M. S. Karawya, S. M. Abdel Wahhab, and A. Y. Zaki, A study of the lawsone content of henna, Lloydia, 32, 76-78 (1969). (5) M. R. Verma and J. Rai, Spectrophotometric and chromotographic studies of henna leaf and powder extracts, Indian Standards Institute Bulletin, 20, 495-497 (1968). (6) I. Singh, R. T. Ogata, R. E. Moore, C. W. J. Chang, and P. J. Schener, Electronic spectra of substituted naphthoquinones, Tetrahedron, 24, 6053-6073 (1968). (7) J. A. Medley and M. W. Andrews, The effect of surface barrier on uptake rates of dye into wool fibres, Textile Research Journal, 29, 398-403 (1959).