246    PREPARATION  OF  ARTIFICIAL  COLORING  MATTERS,  ETC. 
C,2H,NO,+12FeO+2HO+A^6Fe203-fCi,H,N4-A. 
One  part  of  nitrobenzole  is  placed  in  a  retort  with  an  aqueous 
solution  of  acetate  of  iron.  The  retort  is  then  heated  over  a 
water-bath  for  several  hours,  and  then  the  contents  are  filtered 
— being  diluted  with  water  if  thej  have  become  pasty.  The 
residue  left  on  the  filter,  which  is  principally  hydrated  peroxide 
of  iron,  is  washed  with  boiling  water.  The  filtrate  and  wash- 
ings are  then  distilled,  the  condensed  products  being  water, 
acetic  acid,  and  acetate  of  aniline.  These  may  be  again  dis- 
tilled with  strong  sulphuric  acid  (using  four-tenths  the  weight 
of  the  nitrobenzole  employed)  to  recover  the  acetic  acid  and 
form  sulphate  of  aniline,  and  the  latter  may  be  decomposed  by 
caustic  potash  and  the  aniline  distilled  off.  This  process  has 
not  been  found  advantageous,  and  has  consequently  been 
given  up. 
4.  Reduction  of  Nitrobenzole  hy  means  of  Arsenite  of  Potash 
or  Soda. — This  process  was  invented  by  Wohler.  He  digested 
nitrobenzole  with  a  solution  of  arsenious  acid  in  a  strong  ley  of 
caustic  soda,  or  placed  the  arsenical  solution  in  a  tubulated 
retort,  heated  it  to  the  boiling  point,  and  then  allowed  the  nitro- 
benzole to  fall  in  drop  by  drop.  Under  these  circumstances 
nitrobenzole  is  transformed  into  aniline  which  distils  over,  and 
it  is  only  necessary  to  saturate  with  an  alcoholic  solution  of 
oxalic  acid  to  obtain  perfectly  pure  oxalate  of  aniline. 
The  last  method  of  forming  aniline  we  shall  quote,  is  that  of 
Schlagdenhausen,  who  has  shown  that  it  is  produced  when  nitro- 
benzole and  sulphide  of  carbon  are  heated  together  in  a  sealed 
tube  to  160^. 
Properties  of  Aniline.*— Aniline  when  pure  is  a  colorless 
liquid,  very  astringent,  having  an  aromatic  odor,  and  an  acrid 
burning  taste.  It  is  slightly  soluble  in  water,  and  very  soluble 
in  alcohol  and  ether.  Its  sp  gr.  —1-028  ;  at  —-20^  it  does  not 
freeze.  It  boils  at  182*^,  and  distils  unchanged.  When  warmed, 
it  dissolves  sulphur  and  phosphorus.  It  is  a  powerful  base, 
combining  with  acids  to  form  salts,  which  in  general  are  soluble. 
It  decomposes  ferrous  and  ferric  salts,  and  the  salts  of  zinc  and 
alumina,  precipitating  from  them  the  metallic  oxides.    It  also 
*Gerhardt,  Chimie  Organ,  iii.  p.  84. 
