Dr. Hofmann on the MetamorpJioses of Indigo. 401 



violet-red and then gradually turbid and brown. The action 

 is much hastened by the addition of alcohol, by which at the 

 same time, however, acetic aether is formed. By long-con- 

 tinued action the fluid becomes again colourless, and a yellow 

 crystalline matter is obtained, which can be easily purified by 

 washing with alcohol and tether, in which it is but little soluble. 



This substance crystallizes from boiling alcohol on cooling 

 in small yellow plates. By slowly heating it sublimes without 

 residue in the form of beautiful glittering scales of a golden 

 colour. Potash forms with it a blood-red solution, from which, 

 after some time, ruby-red prisms separate, which become of a 

 vermilion colour by moistening with hydrochloric acid, and 

 after removal of the acid dissolve in pure water with a beau- 

 tiful violet colour. All these phaenomena characterize in an 

 undoubted manner the chloranil discovered by Erdmann in 

 his investigations on indigo, a substance which, as I proved* 

 a few months ago, is formed also in many other processes. 



If the action of the oxidizing mixture on the chloraniline is 

 not allowed to go so far, the chloranil is obtained mixed with 

 a viscid matter, which is very soluble in alcohol and aether. 

 On evaporating off the aether and submitting the resinous re- 

 sidue to distillation, oily drops pass over and crystallize in the 

 neck of the retort. They possess the characteristic smell and 

 peculiar reactions which distinguish the chlorophenissic or 

 chlorophenussic acid of Laurent, namely the forming a violet 

 precipitate with sulphate of copper, and a citron yellow with 

 nitrate of silver. 



The formation of all these bodies is easily explained. The 

 nitrogen with a portion of the hydrogen forms ammonia, the 

 presence of which can be proved in the mother-liquor. The 

 remaining hydrogen is entirely or partially replaced by chlo- 

 rine, chlorine and oxygen being called into action in the mix- 

 ture of hydrochloric acid and chlorate of potash, whilst at the 

 same time oxygen enters into the compound. 



The following formulae show the reactions : — 



Ci2{ cf } N + 5C1 + 40 = Cn CI4 O4 + NH3 + 3C1 H. 



* , ' ^^ ^ — -—J 



Chloraniline. Chloranil. 



C,,{ gf } N -f 2H0 + 4C1 = C,2{ ^f^ } O, HO -f NH3 + 2C1 H. 



Chloraniline. Chlorophenissic acid. 



Cijj {^f }n + 2HO + 8C1 = Cli2ClsO,HO + NH3 + 4Cl H. 



Chloraniline. Chlorophenussic acid. 



* Mem. Chem. Soc. vol. ii. p. 227. 

 Phil. Mag. S. 3. Vol. 26. No. 174. May 1845. 2 E 



