16 GIBBS. 



THE COLORATION OF ANILINE IN THE PRESENCE OF OXYGEN IN THE DARK. 



Tubes of pure, dry aniline in contact with purified dry atmospheric 

 air, prepared with great care as previously described, were wrapped in 

 several coatings of tin foil to exclude the light, and heated in a steam 

 bath in the same manner as described in the work on phenol. 28 The 

 coloration appeared in a considerably shorter space of time than that 

 required for the coloration of phenol and became darker with time. At 

 room temperature, 30°, the purest samples of aniline become colored 

 on long standing in the dark. The first shade of color is yellow, which 

 slowly changes on long standing to light red. 



The next paper will deal with the coloration of aniline and some 

 light reactions in the absence of oxygen. 



SUMMARY. 



1. A brief review of the literature of the coloration of aniline is 

 given. 



2. While there can be no doubt that certain impurities will color 

 aniline, the coloration of the pure compound, in the presence of oxygen, 

 is due to oxydation. 



3. The coloration goes on in the dark and is accelerated directly with 

 the temperature. 



4. Sunlight greatly accelerates the reactions involved. 



5. The presence of moisture or impurities are not necessary factors. 



6. Among the products of the light reactions there have been isolated, 

 azobenzene, 2, 5-dianilinoquinone, dianilinoquinoneanil and azophenene. 



7. Ozone reacts instantly with pure, dry aniline or aniline and mois- 

 ture, producing a brilliant red solution. The principal product of the 

 reaction is dianilinoquioneanil. Carbon dioxide is copiously evolved. 



8. The experiments argue against any increased chemical activity of 

 the oxygen due to the oxygen gas ions. 



9. The rate of the color formation in aniline is much greater than 

 in phenol. 



10. It is evident that the purest aniline is prepared by distillation at 

 reduced pressures and- in atmospheres of indifferent gases. 



20 hoc. ait. p. 149. 



