30 minutes (Figure lC, D ) , Beer’s law is not obeyed. Effect of Cerium(1V) Perchlorate. Ceric perchlorate (0.01F) in 3F perchloric acid gave t h e most sensitive and accurate results for the deterniination of p-aminophenol. The ahsorbance was proportional to the ceriurn(1V) conccntration ovrr t h e range 0.14 to 1.4 mg. per ml. of solution (Table 11). Since the absorptivity of the purple coIored compound formed is low ( E = 1.5 X lo2, at 15 minutes time), the method is primarily intended as a specific qualitative test for p-aminophenol, and an accurate semimicro quantitative method. Beer’s law is obeyed over the range of p-aminophenol concentrations, 0.5 to 5.0 mg. per ml. of solution within a 15-minute development period (Table 11). Since p-aminophenol is autoxidized under ordinary conditions by light, samples of this material should be added directly to the cerium(1V) without dissolution of the sample. Autoxidized p-aminophenol does not react with cerium(1V) to produce a purple color.
tolerated with little effect on t , h ~ over-all accuracy.
l k t
ACKNOWLEDGMENT
=: z
10
2
