40 
ON  CREASOTE. 
of  the  measure  of  the  tar.  The  residue  is  pitch.  Carbolic  acid,  in 
an  impure  state,  is  obtained  from  the  above  heavy  oil,  by  agitating 
'  'it  with  strong  caustic  lye ;  but,  as  the  crude  coal  oil  contains  a 
large  per  centage  of  napthaline  and  other  impurities,  I  prefer  to 
rectify  it  and  collect  the  product  in  two  separate  portions,  the  first 
of  which  should  be  used  for  the  preparation  of  creasote.  In  this 
rectification,  it  is  convenient  to  use  twelve  parts  of  the  crude  heavy 
oil,  distil  off  eight  parts  of"  rectified  oil,"  change  the  receiver,  and 
continue  the  distillation  nearly  to  dryness.  The  second  portion  of 
the  distilled  product  contains  an  abundance  of  napthaline,  which 
is  most  easily  removed  by  continually  using  this  portion  over  again 
in  subsequent  rectifications,  by  adding  it  to  more  crude  oil,  sufficient 
to  make  twelve  parts  of  another  operation.  By  continually  using 
this  crude  portion  over  again,  in  the  above  manner,  the  napthaline 
and  other  impurities  are  removed,  by  drawing  off  the  residue  re- 
maining in  the  still  at  the  end  of  each  rectification. 
By  exhausting  the  rectified  oil  with  a  strong  solution  of  caustic 
soda,  about  twenty-five  per  cent,  of  carbolic  acid  is  obtained  from 
it.  The  caustic  soda  should  be  as  strong  and  as  free  from  carbonic 
acid  as  possible,  and  for  this  purpose  it  cannot  be  well  prepared 
by  the  cold  process  of  leeching,  which  is  used  by  soap  manufacturers. 
I  have  succeeded  best  by  boiling  one  pound  of  soda  ash  with  one 
gallon  of  water,  and  then  adding  to  the  boiling  solution  one  pound 
of  hydrate  of  lime,  in  small  portions  at  a  time,  and  after  boiling 
fifteen  minutes,  covering  the  vessel,  and  letting  it  settle  till  cold. 
The  supernatant  lye,  decanted  off  clear,  is  ready  for  use.  A  very 
strong  solution  of  perfectly  caustic  lye  is  thus  obtained,  but  if  less 
lime  or  more  water  be  used,  it  will  not  answer  well.  It  is  almost 
impossible  to  filter  the  strong  lye  through  the  lime  residue,  but,  if 
it  is  left  until  cold,  the  residue  becomes  hard  and  firm,  and  the  lye 
may  then  be  easily  decanted,  The  lime  residue  may  then  be  washed 
with  another  gallon  of  water,  left  to  settle,  decanted,  and  this 
dilute  solution  used  instead  of  water  for  making  the  strong  lye  in  a 
subsequent  operation.  The  hydrate  of  lime  for  the  above  purpose  is 
best  prepared  by  slacking  it  with  one-third  its  weight  of  water,  in 
a  vessel  loosely  covered,  and  leaving  the  mixture  till  the  aqueous 
vapor  has  combined  with  a  small  portion  of  lime,  which  would 
otherwise  remain  anhydrous. 
The  best  plan  for  obtaining  the  creasote  is  to  mix  the  rectified 
