478 Dr. A, W, Hofmann [April 11, 



The transformation of benzol into nitrobenzol, discovered by Mit- 

 scherlich, is only a preparatory operation for the production of aniline. 

 The method of converting nitrobenzol into aniline was discovered by 

 Zinin. It consists in submitting nitrobenzol to the action of nascent 

 hydrogen. Under the influence of this agent, the compound atom 

 N Oa , which in nitrobenzol is associated with phenyl, is decomposed ; 

 its oxygen is converted into water, the residue of nitrogen and phenyl 

 assimilating the necessary quantity of hydrogen to form phenylated 

 ammonia^ or aniline. 



Nitrobenzol. Hydrogen. Water. Aniline. 



(C«H,)NOO + HH+HH + HH = g|o+ h[^+ 'h In 



The hydrogen necessary for this transformatioii may be furnished 

 by numerous processes. The most convenient method for our pur- 

 pose consists in submitting nitrobenzol to the action of metallic iron 

 and acetic acid, a process first proposed by M. Bechamp. I mix the 

 three bodies in a glass retort, and on application of a gentle heat 

 you observe how immediately a most powerful reaction manifests 

 itself. Let us hasten to connect the retort with a condenser ; I have 

 removed the gas-burner from the retort ; nevertheless the reaction 

 continues, and a considerable quantity of water, covering an oily layer, 

 has already accumulated in the receiver. This oily liquid is aniline. 

 We recognize it at once by its peculiar deportment with a solution of 

 chloride of lime. On pouring a single drop of our distillate into 

 this beaker which contains a solution of chloride of lime, a splendid 

 purple cloud is almost instantaneously diffused throughout the liquid. 

 You perceive we are approaching our subject. The beautiful colour 

 which aniline strikes with a solution of chloride of lime has been long 

 known. A solution of bleaching powder has always been used as a 

 test for aniline ; indeed it was by this colour-reaction that the presence 

 of our compound in coal-tar-oil was first pointed out, a fact recorded 

 in the name Kyanol (blue oil), originally given to aniline prepared 

 from coal-tar. Several other oxidizing agents, chromic acid for in- 

 stance, were likewise known to produce coloured compounds from 

 aniline ; but all the colours thus obtained were of an highly ephemeral 

 character. Observe how the purple cloud which I produced by 

 means of chloride of lime has rapidly changed to a dingy reddish 

 precipitate. It was Mr. W. Perkin who had first the happy idea 

 of investigating the circumstances under which this beautiful purple 

 might be prepared in a form permanent and applicable for the pur- 

 poses of the dyer. He succeeded in isolating this colour by submit- 

 ting, under appropriately selected circumstances, aniline to the action 

 of bichromate of potassium and sulphuric acid. 



Here then you have, step by step, the development of this new and 

 important branch of chemical industry. 



Through the kindness of my friend, Mr. Perkin, 1 am enabled to 

 exhibit to you magnificent specimens of his aniline purple, or Mauve, 



