U4 
Crude  Carbolic  Acid. 
t  A-m.  Jour.  Pharm. 
1      March,  1894. 
as  carbolic  oil.  The  light  oil  which  boils  between  90  and  2500  C. 
contains  from  4  to  10  per  cent,  of  acids,  and  therefore  nearly  all  of 
the  carbolic  acid,  or  true  phenol,  boiling  at  1820. 
The  dead  oil  contains  from  10  to  20  percent,  of  acid,  the  carbolic 
oil,  if  made,  sometimes  shows  as  high  as  30  per  cent.  These  oils 
contain  also  a  certain  amount  of  carbolic  acid,  but  the  proportion  is 
much  less  than  in  the  light  oil. 
In  Europe,  where  most  of  the  crystal  carbolic  acid  is  made,  the 
fractions  are  collected  differently.  The  first  portion  running  from 
the  still  containing  most  of  the  benzol  and  toluol  is  called  crude 
naphtha  or  first  runnings.  The  second  portion,  which  is  collected 
as  long  as  the  distillate  is  lighter  than  water,  is  called  light  oil  or 
second  runnings,  and  is  very  rich  in  phenol.  The  third  fraction  con- 
stitutes the  carbolic  oil.  The  portion  to  be  extracted  is  agitated 
with  a  weak  solution  of  caustic  soda,  about  10  per  cent,  is  the  right 
strength.  If  a  strong  solution  is  used,  many  impurities  contained 
in  the  oils,  especially  naphthaline,  are  also  dissolved  and  contami- 
nate the  finished  acid.  After  agitation  the  mixture  on  standing 
separates  into  two  layers, — the  upper  consisting  of  the  extracted 
oil — the  lower  the  solution  of  carbolate  of  soda.  This  latter  is 
drawn  off,  and  on  acidifying  with  either  sulphuric  or  hydrochloric 
acid,  the  tar  acids  are  liberated,  and  float  on  the  surface  as  an  oily 
layer,  holding  more  or  less  water  in  solution,  depending  on  the 
nature  of  the  acid  present.  For  convenience  in  consideration,  we 
will  arbitrarily  divide  the  crude  acids  into  two  classes. 
(1)  Crude  acids  for  the  manufacture  of  crystal  carbolic  acid. 
(2)  Crude  acids  for  disinfecting  purposes. 
Acids  of  the  first  class  are  not  a  regular  commercial  article  in  the 
United  States,  as  there  is  only  one  firm  manufacturing  crystal  car- 
bolic acid,  but  in  Europe,  especially  in  England,  they  are  prepared 
on  a  very  large  scale.  As  their  value  depends  on  the  amount  of 
crystal  acid  they  contain,  they  are  sold  by  test.  Crystal  carbolic 
acid  being  the  first  of  the  series  of  phenols  has  the  lowest  boiling 
point.  Therefore,  the  boiling  point  of  a  crude  acid  is  to  a  great 
extent  an  indication  of  its  value. 
In  England,  an  arbitrary  method  has  been  devised  by  Lowe,  which 
gives  an  approximate  idea  of  the  value  of  these  acids.  A  sample 
(say  100  cc),  is  distilled  in  a  retort  or  flask.  At  first  water  passes 
over,  then  an  oily  liquid.    When  10  cc  of  this  latter  have  been  col- 
