144 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS form 4-fluoro-3-nitroaniline, followed by reaction with ammonia to re- place the fluoro group. The solubility of nitro-p-phenylenediamine at 25øC in aqueous solution at a pH of 9.7 is 0.23% (1). Comparable analy- ses of this intermediate before and after recrystallization are given in Table II. Table II Analyses of Nitro-p-phenylenediamine Purified Raw Purity, % 98.1 90.1 Ash, % Trace 0.20 Iron, ppm Trace 363 Melting point (Fisher-Johns), øC 143.6 134.0 In the ageing test previously described, precipitation in the solution containing the crude product started after 11 days, both at room tempera- ture and at 50øC, while no precipitate appeared in bottles containing the purified material after ageing for 4 weeks. The infrared spectrograms for nitro-p-phenylenediamine are shown in Figs. 2 and 3. Certain reversals in the peaks, especially in the range 4000 30'00 2000 1500 CM" 1000 900 800 700 10C 100 __8C B0 •6C 60 •4C 40 Z •- 2C 3 4 5 6 7 8 9 10 11 12 13 14 WAVELENGTH JMICRONS) Figure 2. Crude nitro-p-phenylcncdiamine 4000 30'00 2000 1500 C• -I 1000 900 800 700 100 100 •.80 80 •o • 40 j.,o , •- 20 210) 3 4 5 6 7 8 9 10 11 12 13 14 1 WAVELENGTH (MICRONS) Figure 3. Purified nitro-p-phenylenediamine

INTERMEDIATES FOR HAIR COLORS 145 of wavelengths from 6.4 to 7.3 v, indicate that differences do exist be- tween the crude and purified products but sufficient data are not avail- able to determine fully the exact nature of these differences. In the laboratory recrystallization of nitro-p-phenylenediamine from water, a mass of sticky material was removed during the hot filtration. This material was washed repeatedly, on the filter, with hot water, until the flitrate came through colorless. After drying at 50øC, and cooling, this black material became very hard. It melted at 98øC. The material had an ash content of 0.67% and an iron content of 0.52% determined and reported as ferric oxide. An infrared spectrogram of this sludge is shown in Fig. 4. 4000 30• 2000 1500 CM a 1000 900 800 700 IOO IOO 80 80 •6o •40 •.0 •- 20 •0 3 4 5 6 7 8 9 10 II 12 13 14 153 WAVELENGTH (MICRONS Figure 4. Sludge from nitro-p-phenylenediamine Nitro-p-phenylenediamine differs from nitro-o-phenylenediamine in that reducing agents are not used in its preparation its solubility in wa- ter, while still low, is about eight times that of the ortho compound it is recrystallized from water instead of alcohol and it is much more difficult to reduce to 1,2,4-triaminobenzene. The sludge from nitro-p-phenylene- diamine melted at 98øC, compared to above 335øC for the ortho com- pound. This fact, in conjunction with the infrared spectrograms of the sludges, indicates that the two compounds are vastly different. Although precipitation in the base solution, of the crude para product, takes longer than with the ortho compound, it does occur. However, recrystallization of the crude product does remove the material that is responsible for the development of a precipitate on ageing. The amount of material precipitated in the boiling experiment, pre- viously described, was 2.13% for the crude nitro-p-phenylenediamine and 0.10% for the purified.