520 



tried to accomplish the final reduction of nitrophenylamine by the 

 protracted action of sulphide of ammonium or potassium, without, 

 however, obtaining definite results. Nor have Messrs. Church and 

 Perkin, who have examined the action of nascent hydrogen upon 

 dinitrobenzol, been more successful. Their experiments have led 

 them to the discovery of an interesting new compound, nitroso- 

 phenyline; but the formation of a diatomic ammonia was not observed. 

 M. Zim'n, on the other hand, to whom science is indebted for the 

 important discovery of the reduction of nitro-compounds, has been 

 more fortunate : by exhausting the action of sulphide of ammonium 

 upon dinitrobenzol, this chemist has in fact obtained a substance to 

 which he attributed the formula set forth for phenylene-diamine. The 

 properties of the body described by Zinin under the name of semi- 

 benzidam, are, however, far from those which might have been anti- 

 cipated in the case of such a compound. Distillation of an alcoholic 

 solution of dinitrobenzol with sulphide of ammonium, according to 

 Zinin (Gerhardt, Traite, vol. iii. p. 104), leaves a brown resinous 

 substance, soluble in water and containing much free sulphur. By 

 dissolving it in boiling alcohol or ether, the compound is deposited, 

 on cooling, in yellow flakes, melting under water to a brown resinous 

 mass, which, on exposure to the atmosphere, rapidly assumes a green 

 colour. This certainly is not the phenylene-diamine of our theoretical 

 conceptions; and more than a year ago, when submitting to the 

 Society some experiments on the action of nitrous acid upon nitro- 

 phenylene-diamine*, I was led to express this opinion: "Those 

 chemists who have had an opportunity of becoming acquainted 

 with the well-defined properties of ethylene-diamine, will not be 

 easily persuaded to consider the uncouth dinitrobenzol-product 

 sometimes appearing in brown flakes, sometimes as a yellow resin, 

 rapidly turning green in contact with the air as standing to smooth 

 phenylamine in a relation similar to that which obtains between 

 ethylene-diamine and ethylamine." I have in no way to retract the 

 opinion then expressed. The diatomic ammonia of the phenyl-series 

 has obviously never been observed in a pure state. Phenylene- 

 diamine and the homologous diatomic aromatic bases are as well- 

 defined substances as their collateral monamines. This class of bodies 

 is, in fact, characterized by an extraordinary crystallizing power, both 

 * Proceedings of the Royal Society, vol. x. p. 495. 



