PREPARATION  OF  ARTIFICIAL  COLORING  MATTERS,  ETC.  129 
ON  THE  PREPARATION  OF  ARTIFICIAL  COLORING  MATTERS 
WITH  THE  PRODUCTS  EXTRACTED  FROM  COAL  TAR. 
By  M.  E.  Kopp, 
(Continued  from  page  47.) 
Extraction  of  Aniline  from  Coal  Tar. — The  method 
which  appears  to  be  the  most  rational,  and  which  deserves  to  be 
tried,  would  consist  in  treating  the  tar  as  condensed  in  gas  works, 
with  hydrochloric  or  sulphuric  acid,  diluted  with  3  or  4  times  its 
volume  of  water.  Mechanical  means  for  affecting  the  intimate 
mixture  of  the  tar  with  the  acid  might  be  easily  contrived,  but 
in  the  absence  of  any  special  contrivance,  the  end  may  be  at- 
tained by  half  filling  a  barrel  with  the  tar,  adding  one-fifth  or 
one-sixth  its  volume  of  acid,  and  rolling  and  shaking  the  barrel 
until  the  acid  has  taken  up  all  the  bodies  with  which  it  is  able 
to  combine  ;  the  whole  might  then  be  run  into  a  cistern,  where 
by  degrees  the  watery  liquid  would  separate  from  the  tar.  The 
same  acid  liquid  might  be  used  over  and  over  again,  until  the 
bases  had  nearly  saturated  the  acid.  A  very  impure  aqueous 
solution  would  thus  be  obtained,  but  containing  the  hydrochlo- 
rates  or  sulphates  of  ammonia,  and  all  the  other  organic  bases 
contained  in  the  tar,  such  as  aniline,  quinoline,  pyrrol,  picoline, 
pyrrhidine,  lutidine,  toluidine,  cumidine,  &c.  By  evaporating 
this  solution  almost  to  dryness,  and  then  distilling  with  an  ex- 
cess of  milk  of  lime,  the  bases  would  be  set  at  liberty.  Am- 
monia, as  the  most  volatile,  would  be  disengaged  first,  and 
might  be  condensed  apart,  and  by  raising  the  temperature  higher 
and  higher  the  other  bases  would  be  disengaged.  Aniline  would 
be  found  among  the  liquids  distilling  between  150^  and  250^  C. 
The  manipulation  of  the  tar,  however,  is  an  extremely  disa- 
greeable operation,  and  presents  many  difiiculties  ;  it  is  there- 
fore preferable,  in  most  cases,  to  distil  the  tar  first,  and  only 
operate  on  the  most  pure  and  limpid  distilled  oils. 
Aniline,  because  of  its  high  boiling-point,  is  never  met  with 
in  the  light  and  volatile  liquids  which  first  distil  from  tar.  The 
most  of  it  is  found  in  those  which  distil  between  150°  and  230^ 
C.  These,  according  to  Hofmann  contain  about  10  per  cent,  of 
organic  bases,  mostly  aniline  and  quinoline.    The  oils  which 
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