434 GIBBS. 



Tubes numbers 1, 2, and 3 colored most rapidly, a light yellow color 

 being visible in seven minutes. Very slight differences were noticeable, 

 but if any distinction is to be made number 1 colored most rapidly. In 

 five days these tubes were a brilliant, dark red. 



Tubes numbers 4, 5, 6, 7, 8 and 9 colored more slowly than the three 

 first mentioned and very distinct differences were noticeable. Those 

 under reduced pressure colored more slowly than those at atmospheric 

 pressure. 



Tubes numbers 10, 11 and 12 colored slowly and in the reverse order 

 of the tubes sealed in an atmosphere of hydrogen. The tubes at reduced 

 pressure, containing less carbon-dioxide, colored more rapidly than the 

 tube at atmospheric pressure. A peculiar difference from all the other 

 tubes was noted in these three. The coloration produced by the first day's 

 exposure (of two hours' duration) entirely disappeared during the night 

 while the tubes were standing in the dark. The coloration produced 

 during the second day's exposure did not disappear during the follow- 

 ing night. 



Tubes numbers 13, 14 and 15 showed a light yellow color in one hour 

 and in five days were a bright red color. 



Tubes numbers 16, 17 and 18 remained colorless for five days. At 

 this time a faint yellow became visible. The color deepened very slowly 

 and at the end of sixty days was still very light. 



At the end of sixty days' exposure some of the tubes were opened and 

 the results of a study of the reaction products agreed with the those 

 already recorded in other experiments on aniline. Methylamine was 

 identified in tubes numbers 13 and 15. 



Small quantities of the red monomethylaniline were distilled and the distillate 



N 

 collected in an — solution of hydrochloric acid. The acid solution was evaporated 



spontaneously in a vacuum desiccator over calcium chloride. On treating the 

 residue with a concentrated solution of potassium hydroxide, alkaline vapors 

 were given off which had the characteristic odor of methylamine. 



SUMMARY. 



I. Aniline, purified in a number of different ways, and sealed in the 

 atmosphere of an indifferent gas, or in vacuo, colors in the sunlight. 



II. The products formed by the reaction are azophenine, benzene and 

 ammonia. 



III. The red coloration is caused by azophenine in solution. 



IV. The pressure of the indifferent gas in the tube has some influence 

 upon rate of coloration. 



V. Carbon dioxide is not an indifferent gas since it has a tendency to 

 retard the rate of coloration. 



VI. Methylaniline also undergoes a chemical change in an atmosphere 

 of hydrogen, with the production of an intense red solution. 



