COMPOUNDS CAUSING KED COLORATION OF ANILINE: I. 15 



several times. The aniline thus obtained had a constant boiling' point. As a 

 further precaution to avoid the presence of sulphur compounds, a portion of this 

 product was further purified by the method of Hantzsch and Freese 23 by boiling 

 with acetone. The final drying was accomplished by distilling with a small 

 piece of metallic sodium in the manner previously described 24 and only the 

 middle refraction employed. This was received in the flask / of the apparatus 

 shown in fig. I, 25 a small piece of sodium introduced, the tube sealed and the 

 procedure employed in the investigation of phenol was carried out in the same 

 manner. In some respects aniline is more easily handled than phenol. 



The liquid thus obtained showed no color visible to the eye. When 

 oxygen was excluded b} r inclosing it with an atmosphere of an indifferent 

 gas. it remained unchanged for two months, as long as the observation 

 lasted, in the diffused light of the laboratory. 



"When scaled in thin glass tubes with puisfied. dry atmospheric air, 

 consisting only of indifferent gases and oxygen, the aniline colored ra- 

 pidly in the sunlight, a few minutes' v exposure being sufficient to produce 

 a light red color. The change takes place with remarkable rapidity. 

 When the sun is near the zenith at noon in either the months of April, 

 May or August I have watched a tube of pure, colorless aniline darken 

 and assume a decided red shade in less than ten minutes. The tempera- 

 ture is an important factor of the rate of the reaction. 



Since one of the first products to be formed is water, the reaction 

 products in general will be the same as those previously described in the 

 experiments where no effort was made to exclude moisture. This experi- 

 ment merely proves that moisture is not necessary to start the reaction. 



TTTE ACTION" OF OZONE ON ANILINE. 



On contact with ozonized oxygen, colorless dry aniline behaved in ap- 

 pearance in the same manner as liquid phenol. Coloration was instantly 

 produced and gradually deepened from yellow to a very dark red as the 

 action progressed. The presence or absence of the ion filter, G, described 

 in the work on phenol, produced no visible effect. In the beginning- 

 no carbon dioxide was envolved, but as the reaction proceeded large quan- 

 tities were given off. The aniline finally became so saturated with the 

 reaction products that crystals separated and eventually the whole became 

 almost a solid mass of crystals. When viewed by the microscope these 

 were seen to be dianilinoquinoneanil. JTo other crystals were detected. 



Aniline which had not been purified with any great degree of care 

 behaved, in the presence of moisture and ozone, as far as was observed, 

 in the same manner. Dianilinoquinoneanil was the principal product 

 formed. 



23 Loc, cit. 



21 The Oxidation of Phenol: This Joum., Sec. A. (1909), 4, 137. 



2 'Ibid., p. 136. 



