THE COMPOUNDS WHICH CAUSE THE RED COLORATION 

 OF ANILINE: II. THE EFFECT OF SUNLIGHT IN THE AB- 

 SENCE OF OXYGEN AND OXIDIZING INFLUENCES 

 AND A COMPARISON WITH THE BEHAVIOR 

 OF MONO- AND D1METHYLANILINE. 



By H. D. Gibbs. 

 (From the Division of Organic Chemistry, Bureau of Science, Manila, P. I.) 



In the first paper on The Compounds which Cause the Coloration of 

 Aniline 1 I have shown that, in the presence of oxygen, oxidation is the 

 principal factor. The major products of the reactions are 2,5-dianilino- 

 quinone, dianilinoquinoneanil and azophenine, all of which are very 

 soluble in aniline with the production of brilliant red solutions. Other 

 oxidation and condensation products may be formed and are doubtless 

 present in minor quantities. The rate of coloration is greatly accelerated 

 by sunlight and active forms of oxygen such as ozone and hydrogen 

 peroxide. 



Since it- was found 2 that neither pure phenol, moist crystals, nor a 

 solution of the crystals in water are affected by sunlight when exposed in 

 sealed glass tubes in atmospheres of nitrogen, hydrogen, or carbon dioxide, 

 the same experiments have been performed with aniline with very 

 surprising results. The coloration has been found to take place in the 

 absence of oxygen or oxidizing influences with remarkable rapidity in the 

 sunlight of this locality. On a day when the actinic value of the sunlight 

 was far from the maximum 3 a yellow color was first visible in seven 

 minutes. In less than one month some samples, in atmospheres of an 

 indifferent gas, became a brilliant, dark red, when viewed in a thin layer, 



'-This Journal, Sec. A (1910), 5, 9. 



-Gibbs, Ibid., Sec. A (1908), 3, 361; (1909), 4, 133. 



3 Comparative measurements, which will be published later, of the activity 

 of the sunlight as measured by the decomposition of a uranyl acetate-oxalic acid 

 solution have been carried on daily for almost a year. On the day above referred 

 to, September 30, 1910, the decomposition was only 60 per cent of the observed 

 maximum day. 



419 



