150 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ments, the resulting color of the mixture can readily be predicted both qualitatively and quantitatively. This cannot always be done with oxi- dation dye intermediates if the prediction is made solely on the basis of the color formed when the intermediate is oxidized by itself. Another un- predictable behavior is that color intensity resulting from certain combina- tions of intermediates may be considerably greater or less than expected. Many of these dye coupling reactions are quite pronounced and exten- sive use of them are made in modern oxidation dyes. Outstanding ex- amples are the blue and purple shades from mixtures of para diamines and meta diamines, purple shades from p-phenylene diamine and alpha naph- thol, bright red from p-amino phenol and alpha naphthol, and of course the many interesting and valuable color modifications when the poly- hydroxy phenols are used with p-phenylene diamine. In all of these ex- amples a color change resulted by oxidizing a primary dye intermediate in the presence of a secondary dye intermediate. Less obvious is the fact that mixtures of primary intermediates can result in unexpected color changes. This was demonstrated in the following experiment. Hair swatches were dyed for thirty minutes in each of the following four dye preparations. An alcoholic ammonium oleate base was used with the pH adjusted to 9.6 with ammonia. A. p-phenylene diamine 0.3%, resorcino10.3% B. p-phenylene diamine 0.3%, resorcinol 0.6%, o-amino phenol 0.3% C. p-phenylene diamine 0.3%, resorcinol 0.6%, m-amino phenol 0.3% D. p-phenylene diamine 0.3%, resorcinol 0.6%, p-nitro-o-amino phenol 0.3% The resulting colors were (A) greenish blonde, (B) light ash brown, (C) light brown-violet cast, (D) purplish brown. Hair swatches which had been dyed in preparation (A) for thirty minutes were then re-dyed in each of the following preparations which consisted of the same dye base also adjusted to a pH of 9.6 with ammonia. E. p-phenylene diamine 0.3%, resorcinol 0.3% F. o-amino phenol 0.3%, resorcinol 0.3% G. m-amino phenol0.3%, resorcinol 0.3% H. p-nitro-o-amino phenol 0.3%, resorcinol 0.3% The color of the re-dyeings were all greenish blonde to ash blonde. The colors were additive in this case and behaved like direct dyes. POLYHYDROX¾ [PHENOLS AS COLOR MODIFIERS One other but very essential group of dye intermediates are the phenolic compounds. Although they produce little if any color on the hair when

COLOR REACTIONS OF OXIDATION DYE INTERMEDIATES 151 used alone, they have a pronounced effect on the resulting hair color when used in conjunction with primary dye intermediates, especially p-phenylene diamine. All of these compounds, with the exception of alpha naphthol, are polyhydroxy phenols and they include the following: resorcinol, pyro- gallol, hydroquinone, phloroglucinol, pyurocatechol, alpha naphthol and dihydroxynaphthalene. The color changes produced by the phenols were described by Kass (2) in 1956. The phenols are not only valuable color modifiers but can also act as stabilizers, antioxidants and chemical timers to control the rate of color development. Resorcinol is extensively used as a drabbing agent for p-phylene diamine which usually yields brown tones with a violet cast. When resorcinol is used more desirable drab or greenish brown tones result. Alpha naphthol, on the other hand, yields violet to purple shades with p-phenylene diamine but because of its higher molecular weight its use may result in low intensity dyeings. p-phenylene diamine, although very color sensitive to the presence of other aromatic compounds, is not unique in this respect. P-amino phenol dyeings can also be modified. This compound when used alone results in reddish blonde shades but in the presence of alpha naphthol, distinct pink shades result. THE META DIaMINES The meta compounds, particularly the meta diamines, are classified as color couplers. When oxidized in the presence of para diamines they couple or condense with the quinone-di-imine to form intense blue or purple indamine dyes which have a high affinity for hair. The purple dye formed when alpha naphthol and p-phenylene diamine are oxidized together is an indophenol dye. The blue or purple dye formed when a meta diamine and a para diamine are oxidized together is an in- damine dye. This latter reaction is extensively used to obtain such shades as platinum, silver, steel gray and smoke blondes. Unfortunately, these colors are not as stable as dyes resulting from the oxidation of primary inter- mediates alone. We are speaking now of color stability on the hair. The blue and purple shades resulting from oxidizing a para diamine such as p-phenylene diamine in the presence of a meta diamine such as m-phenylene or m-toluylene diamine tend to turn red on the hair. Several years ago, in the course of investigating this problem, hair dyeings were made using various combinations of para diamines and meta diamines. No attempt was made to stabilize the blue and purple dyeings. When examined many months later, they had all drastically changed color with several becoming bright red. A possible explanation of this may be of interest. When a para diamine is oxidized in the presence of a meta diamine, a blue or purple indamine dye results which can readily undergo further oxidation with ring