C()LORING WiTH SEMIl'ERMANENT DYES 381 such as 4-methoxycatechol, are applied from a 1% solution at a pH of 7. In still another method (8), 1,2,4-trihydroxybenzene is applied from a 2% aqueous alkaline solution. In a recent U.S. patent (9), the use of 2,5-di- hydroxymonoethylaminobenzene is revealed. A cid Dyes Acid dyes, that were developed for the textile industry and are being used for semipermanent hair coloring, include regular acid dyes, metal- lized dyes, and chrome colors. The regular acid dyes include azo dyes (10), anthraquinone dyes (11), azine, xanthene, and triphenylmethane- type dyes (12). Acid dyes are generally applied from an aqueous solution at a pH range from 2.5 to 4.0 but in one of the patents cited above (11), a pH range of 8.0 to 10.0 is used for dyeing with aliphatic amine deriva- tives of anthraquinone dyes. There are two types of metallized dyes that are being used as semi- permanent hair colors. One of these, of which the Irgalan* dyes are typical, contains one atom of metal for every two moles of dye and is classed as the neutral-dyeing type. The other, to which the Neolan* colors belong, contains one atom of metal for each mole of dye and is classed as the acid-dyeing type. These dyes are applied from a 1% aque- ous solution at a pH around 4.0 (12). Chrome dyes, when used as semipermanent hair colors, are generally applied as acid dyes without treatment with any metal salt (12). The color differs from that produced by the same dye when used with chrome but some of the dyes of this series have sufficient fastness properties to be satisfactory when applied in this way. Color Index Mordant Black No. 26 which gives a purple shade of good fastness is an example. Basic Dyes When basic dyes are used in semipermanent hair colors they must be carefully selected in order to achieve satisfactory fastness properties and minimum staining of the scalp. A method for using triphenylmethane, azine, oxazine, and thiazine basic dyes at a pH of 7 to 8, in the presence of an oil, a cationic surface active material, and a thickening agent, is de- scribed in a recent U. $. patent (13). The use of basic azo and anthra- quinone dyes, containing a quaternary ammonium group, is described in a British patent (14). * Geigy Dyestuffs, Saw Mill River Road, Ardsley, N.Y. 10502. t Ciba Chemical & Dye Co., Fair Lawn, N.J. 07410.

382 JOURNAL OF THE SOCIETY OF COSMETIC CItEMISTS Solvent-Soluble Dyes There are two types of colors that can be classed as solvent-soluble dyes. The first, which are the true solvent-soluble dyes, are insoluble in water and include compounds belonging to the azine, azo, anthraquinone, acid-base dye complexes, and azo-metal complexes, all of which are free of solubilizing groups (15). They are applied to hair as 0.5% aqueous dis- persions at an approximate pH of 7.0. The second type of solvent-soluble dye is the dispersed color which was originally developed for dyeing cellulose acetate and consists of mix- tures of solvent-soluble dyes and dispersing agents. They are applied to hair as 1 to 2% aqueous dispersions at a pH of 5.0 to 9.5. Their applica- tion is described in a British patent (15) and in a recent article by Sardo (16). Naphthoquinone Dyes According to a U.S. patent (17), 5,8-dihydroxy-l,4-naphthoquinone (naphthazarin) is applied to hair from a 0.25% aqueous dispersion con- taining ethanol, diethylenetriamine, a surface active material, and a thick- ening agent at a pH of 9.9 to give a strong purple color. In another U.S. patent (18), the application of 1,4- and 1,2-naphthoquinone from an aque- ous solution containing a surface active agent and a thickening agent at a pH range from 8.0 to 10.5 is described. The dyeing of hair with mono- amino 1,6- and 1,7-dihydroxynaphthalenes using a 1% aqueous solution at a pH of 8.0 is described in a British patent (19). In another British patent (20), naphthoquinone imine dyes such as basically substituted 5- amino-8-hydroxy-l,4-naphthoquinone-l-imine are covered. These are applied from a 0.25% aqueous solution containing a solvent, surface ac- tive material, and a thickener at a pH of either 9.9 or 3.5. Fiber-Reactive Dyes As the name implies, the fiber-reactive dyes are fixed on the hair due to the presence of reactive groups in the dye molecule. They are avail- able under the trade names Cibacrons©, * Procions©, * Reactones©, * Dri- marenes©,õ Remazols ©, and others. The application of reactive dyes to * Ciba Chemical 8c Dye Cmnpany, Fair Lawn, N.J. 07410. ? I.C.I. (Organics) Inc., Charlotte, N. C. 28211. • Geigy Dyestuffs, Ardsley, N.Y. 10502. õ Sandoz Inc., Hanover, N.J. 07936. I• American Hoechst Corp., Mountainside, N.J. 07091.