54 The Philippine Journal of Science wn 



nitrophenols in presence of alkali are not quinone bands for the 

 reason that they appear at greater dilutions than in quinone 

 itself is thus seen to be without weight. 



In order to prove that phenoquinone is produced in phenol 

 by oxidation, we have exposed colorless phenol in open vessels 

 to the action of sunlight until it developed a decided red color, 

 after three or four days, and then photographed its absorption 

 spectrum. The curve was found to coincide with that of pheno- 

 quinone dissolved in phenol. The proportion of phenoquinone 

 formed by the action of sunlight and oxygen in a given time can 

 be estimated by comparison with the curves shown in fig. 1. 



Fig. 1. The curves of quinone, phenol, phenoquinone in alco- 

 hol, phenoquinone plus 8 equivalents of phenol in alcohol, and 

 phenoquinone in pure phenol are shown. Our curve of quinone 

 practically agrees with that given by Baly and Stewart, 7 except 

 that the small band in the benzene region heading at 1/A=4100 

 is not shown in their charts. Hartley, Dobbie, and Lauder 8 

 show this band highly developed, but it is probable that the pure 

 compound will show no band in this region of the spectrum. 

 Since quinone is so readily reduced by alcohol in ultra-violet 

 light, it is reasonable to attribute this incipient band to the 

 presence of small quantities of quinol. 



The curves of phenoquinone in alcohol in tenth, hundredth, 

 and thousandth molar concentrations have been previously de- 

 scribed. The absorption band at 1/A=3700 is due to phenol 

 and that at 1/A=4100 to quinone. The curve of phenoquinone 

 with 8 equivalents of phenol obtained with hundredth molar 

 solution is not shown on the chart, since it is almost a straight 

 line and lies very close to that of hundredth molar phenoquinone. 

 The phenol band at 1/A=3700 shows in this solution at log. 1.1, 

 since the phenol is present at one-thousandth molar concentra- 

 tion. 



Fig. 2. Since dianilinoquinone is insoluble in alcohol and in 

 the usual diactinic solvents, it is necessary to employ glacial 

 acetic acid to cover approximately the full range of the absorp- 

 tion spectrum. In order to obtain comparisons of the color 

 band of this compound with those of dianilinoquinoneanil and 

 azophenine, we have also used solutions in aniline and in phenol. 

 The curves are shown in fig. 2. 



'•Ibid. (1906), 89, 507. 



'Rep. Brit. Assoc. (1902), 99. 



