ON  CREASOTE. 
41 
oil  with  an  equal  measure  of  the  strong  caustic  lye,  stir  it  occa- 
sionally for  half  a  day,  draw  off  the  alkaline  solution,  and  again 
treat  the  oil  in  the  same  manner  with  half  the  measure  of  caustic 
soda  first  used.  This  removes  all  the  creasote  contained  in  the  oil, 
if  the  lye  is  good,  and  in  this  case  a  sample  of  the  oil,  agitated  with 
a  little  fresh  lye,  no  longer  gives  to  the  latter  a  dark  color.  It  is 
best  not  to  heat  this  mixture,  as  by  so  doing  the  oil  becomes  rapidly 
oxidised,  and  confers  a  dark  color  on  the  alkaline  solution,  which 
renders  it  difficult  to  be  separated.  After  the  first  treatment  with 
caustic  lye,  a  large  portion  of  the  alkaline  compound  remains  dis- 
solved in  the  supernatant  oil,  which  renders  it  necessary  to  use  a 
second  portion  of  caustic  soda  to  remove  it,  in  the  manner  above 
described. 
The  alkaline  solution  of  creasote  (or  carbolic  acid)  may  be  de- 
composed with  almost  any  acid,  but  strong  sulphuric  acid  is  the 
most  convenient  and  economical,  and  this  produces  a  hot  solution  of 
sulphate  of  soda,  which  becomes  a  crystalline  mass  on  cooling, 
while  the  creasote  separates  readily  to  the  top,  and  may  easily  be 
removed  either  before  or  after  the  crystallization  of  the  sulphate  of 
soda. 
The  crude  creasote  thus  obtained  is  of  a  light  brown  color,  but 
soon  becomes  very  dark,  and  holds  water,  resin,  sulphate  of  soda, 
and  the  substance  which  becomes  brown  by  oxidation.  Of  these 
substances  the  three  first  can  be  removed  by  distillation,  and  the  last 
by  oxidation  and  subsequent  distillation,  but  for  this  purpose  a 
powerful  agent  must  be  resorted  to.  Chromic  acid  is  reduced  by  it 
to  oxide  of  chromium,  but  it  is  not  effectual  in  perfectly  oxidising 
all  of  the  brown  impurity.  Nitric  acid  converts  the  creasote  into 
carbozotic  acid,  and  consequently  cannot  be  used.  Concentrated 
sulphuric  acid  answers  the  purpose  admirably,  and,  in  short,  this  is 
the  only  agent  which  has  proved  effectual  in  the  purification.  For 
this  purpose  the  acid  must  be  in  the  most  concentrated  state,  and 
consequently  the  crude  creasote  must  first  be  rectified,  to  remove 
water  from  it,  before  adding  the  strong  acid,  otherwise  the  latter 
will  become  diluted,  and  less  active. 
In  the  rectification  of  the  crude  creasote,  the  first  portion  which 
passes  over  contains  water,  and  should  be  set  aside,  to  be  again 
separated.  When  no  more  water  passes  over,  the  rectified  product 
should  be  collected  by  itself,  in  a  dry  vessel,  and  the  distillation 
