225 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 5-amino-4 methoxy-2-aminophenol 5-methyl-4 hydroxy-2-aminophenol 4,31,3I, diethylamino-2-aminophenol It is claimed that in many cases hair dyeing recipes based on the above, and other similar compounds, can be formulated which will function with air oxidation alone. Polyhydroxy compounds have also been studied extensively by several firms, for instance a patent (11) describes the use of compounds of the type 0H N•.R• OH such as 2,5-dihydroxymethylaminobenzene. Oxidation can be effected by air or by peroxide addition. It is claimed that allergic manifestations are greatly reduced with such compounds. M-, and o-dihydroxy amines have also been studied, a patent (12) covering compounds of the general type OH and in particular describing the use of 2,4, dihydroxydiphenylamine. o-Dihydroxy compounds based on the general formula 0H where X or A_ or both may be OH ortho to the first OH group, or one of them may be some other substituent. This is taken to include 5 bromo-4-amino catechol 5 methyl 4 amino catechol 5-(• aminoethylamino)-catechol and 5-amino-l,2,$ trihydroxy benzene and has been the subject of another patent (15). A favoured example is 5-bromo-4-amino catechol hydrochloride which can be applied in a

CHEMISTRY OF SYNTHETIC DYES USED IN COSMETICS 229 shampoo base and oxidized in the air. Compounds similar to the above groups are presumably formed when trihydroxybenzene and substituted derivatives are allowed to "ripen" with ammonia for 1-5 days out of contact with air to give a solution which will dye hair by air oxidation (14). Investigations have also been carried out (15) on dihydroxy indole compounds of the general type where R, R• and R2 are simple alkyl substituents. Formulations using such compounds require oxidation with hydrogen peroxide. Benzoquinones, naphthaquinones, and anthraquinones are also covered in a patent (16). INTRINSICALLY COLOURED "OXIDATION" BASES Compounds loosely classed as oxidation bases, such as the nitropheny- lene diamines, particularly nitro p-phenylene diamine, are extensively used as hair dyes being intrinsically coloured and not requiring oxidation. More complicated derivatives of these compounds have been studied extensively (17) for compounds of the general type H--N--R R•"•N•• Rtt NOz have been patented where R, R', and R" can be a variety. of alkyl and hydroxyl alkyl radicals. This patent appears to include compounds similar to those studied earlier (18) which refers more particularly to compounds such as the following NH.CH2. CH 2 OH NH 'CH2'CH• OH OH NO• NHz NO z CHe, CH 2 OH (a bright golden yellow) (reddish violet) (bright brick red )