130   PREPARATION  OF  ARTIFICIAL  COLORING  MATTERS,  ETC. 
distil  above  250°  contain  mostly  quinoline,  and  yery  little 
■aniline. 
The  following  is  Hofmann's  process  for  extracting  the  two 
bases  from  the  oils  and  separating  them.  The  oil  is  agitated 
strongly  with  commercial  hydrochloric  acid.  The  mixture  is 
then  allowed  to  rest  for  12  or  14  hours,  and  the  oil  is  separated 
from  the  acid ;  the  latter  is  treated  again  with  fresh  quantities 
of  oil  until  it  is  nearly  saturated.  The  still  acid  solution  of  the 
hydrochlorates  is  filtered  through  linen  or  wetted  filtering 
paper,  to  retain  the  greater  part  of  the  oil  mechanically  mixed 
with  the  watery  solution  ;  it  is  then  placed  in  a  copper  still, 
?^nd  supersaturated  with  an  excess  of  milk  of  lime.  At  the  mo- 
ment of  saturation  an  abundance  of  vapors  are  given  ofi*,  and 
the  head  must  be  quickly  fixed  on  the  still.  Heat  is  now  ap- 
plied, so  as  to  obtain  a  quick  and  regular  ebullition. 
The  condensed  product  is  a  milky  liquid,  with  oily  drops 
floating  on  it.  The  distillation  is  carried  on  as  long  as  the  va- 
por has  the  peculiar  odor  of  the  first  part  distilled,  or  the  con- 
densed product  gives  the  characteristic  reaction  of  aniline  with 
chloride  of  lime. 
The  milky  liquid  is  now  saturated  with  hydrochloric  acid  ;  it 
is  then  concentrated  in  a  water  bath  ;  and  lastly,  decomposed 
in  a  tall  narrow  vessel  by  means  of  a  slight  excess  of  hydrate 
of  potash  or  soda.  The  bases  set  free,  unite,  and  form  an  oily 
liquid,  which  floats  on  the  alkaline  solution.  This  is  removed 
with  a  pipette  and  rectified.  The  rectified  product  is  aniline, 
sufiiciently  pure  for  industrial  purposes^  especially  if  we  set 
aside  the  part  distilling  above  200°  or  220^,  which  is  princi- 
pally composed  of  quinoline. 
To  obtain  aniline  chemically  pure,  the  neutral  oils  forming 
part  of  the  oily  layer  must  be  completely  removed.  This  is  done 
by  dissolving  the  whole  in  ether,  and  adding  dilute  hydrochloric 
or  sulphuric  acid,  which  combines  with  and  separates  the  bases, 
and  leaves  the  oils  in  solution  in  the  ether.  The  acid  solution 
is  then  decanted,  decomposed  with  potash,  and  submitted  to 
careful  fractional  distillation.  If  the  products  are  gathered 
separately  in  three  parts,  the  first  will  contain  ammonia,  water, 
and  some  aniline ;  the  second  will  be  pure  aniline;  while  the 
third  portion  will  contain  mostly  quinoline.    An  alcoholic  solu- 
