OXIDATIVE DYEING OF KERATINOUS PROTEINS 243 Fen i '] • (v) possibility that Fe• "salt forma- tion" occurs is not excluded. Subsequent work, using wool as the keratinous protein, has shown that T.H.T., which was used for our preliminary work, will impart a reddish-brown to light medium brown dyeing according to the pH of the solution used the color deep- ens with increase in pH but is never brown- black. Simultaneous treat- ment 6f wool with T.H.T. and vari- ous metal salts (Fe•, Cu•, Co•t) causes a marked darkening in the shade which becomes black, dark browrl and dark medium brown,7 respectively, for the metals quoted. The process on living skin can thus t•e •õeparated into two distinct stages with wool. It will be apparent from our mode of formulation of the dyeing processes that part of the original S--S linkings of the fiber have com- bined with benzene nuclei which have been incorporated into the "colored molecule" determinations of the load/extension curves, using human hair treated with T.H.T., show that at pH 4 tl•ere is a change in work of approximately 13.4•per cent over the untreated hair. :: Tfihydroxybenzene'shows a simi- lar behavior to T.H.T. both in absence and presence" of Ferrous salt.' Data on the amount of corn5: bination on hai? are not yet avail- able but are being determined. It is anticipated that results similar to the above will be obtained. It was not until the work described above had been carried out that I realized that the orientation of the three hydroxyl groups in (I).and (II) was the same as in dihydrolaw- sone (1,2,4-trihydroxyn aphthalene), and it was clearly of some interest to study the behavior of this com- pound on skin and wool. Applica- tion of aqueous solutions of this triphenol to skin results in very rapid oxidation to lawsone (2- hydroxy-l,4-naphthquinone), pre- sumably because of an oxidase system in the skin. The dyeing of wool from an aqueous solution im- parts an orange shade but in pres- ence of ferrous ammonium sulfate a dark, medium brown shade results. In lawsone there is only one avail- able position for the addition of the RSH the resulting thiohydroxy- quinone can clearly undergo Fe salt complex formation leading to a structure of type (V). O 0 © [o] OH OH O RSH (vi) :• ß The- stain, produged on,,:skin by lawsone is readily removed by o OH [O ] OH SR SR _ OH O

244 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS washing whereas that from T.H.T., for example, is very persistent. It was considered to be of decided interest to see the result of applying dihydrolawsone in the presence of ammonium thioglycollate to the skin, since the thioglycollate should produce free SH groups. Caution is necessary in the use of such a mixture since blistering of the skin can and often does occur: the re- sulting reddish-orange stain is, how- ever, much more persistent than that from dihydrolawsone alone, indicating that, as expected, more of the compound (VI) has been pro- duced iron complex formation does not occur under these conditions. It is a well-known fact that juglone [5 (8)-hydroxy- 1,4-naph- thaquinone] which is isomeric with lawsone, will stain skin when ap- plied as its colorless dihydro-deriva- tire. This is attributed to the same series of reactions discussed above for T.H.T. leading ultimately to a structure of type (VII). This mole- cule could clearly form a chelated iron salt through the OH group and the quinone O in the peri position. o (VII) The experimental evidence sup- porting the incorporation of the colorless T.H.T. and, by analogy, the other colorless triphenols, to give dyed materials, and the mode of combination suggested in this lecture, has been submitted for pub- lication in the ]ournal of the Society of Dyers and Colorists. The work appears to have a direct bearing on (a) the coloring (oxidative dyeing) of keratinous proteins (skin, hair, wool), and (b) the production of pigments (which are not melanins) in both the animal and vegetable kingdoms. SWELLING STUDIES OF SINGLE HUMAN HAIR FIBERS* By MILTON G. ECKSTP. OM, Raymond Laboratories, Inc., St. Paul, Minn. Tins p^pEu will be divided into two sections. The first portion will contain a description of the swelling apparatus which has been * Presented at the December 5, 1950, Meeting, New York City. used at Raymond Laboratories. In the second payt, the results of sev- eral actual experiments will be given and discussed, especially in their relation to cold permanent waving. Early work on transverse hair