THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
DECEMBER,  i89i. 
SYNTHETICAL  CARBOLIC  ACID. 
By  H.  W.  Jayne. 
Read  at  the  Pharmaceutical  Meeting  of  the  Philadelphia  College  of  Pharmacy,  Nov.  17. 
It  has  been  known  for  some  years  that  carbolic  acid  could  be 
produced  by  numerous  synthetical  methods,  but  interest  in  the  sub- 
ject has  been  especially  manifested  recently  on  account  of  several 
firms,  in  response  to  the  constant  demand  for  purer  preparations, 
having  undertaken  its  manufacture  on  a  commercial  scale.  Of  the 
many  reactions  by  which  phenol  can  be  produced,  only  two  are,  at 
present,  commercially  practical ;  both  using  pure  benzol  as  the 
starting  point. 
The  first  or  sulphonate  method  is  applicable  to  the  preparation  of 
all  phenols  and  has  been  used  for  some  years,  producing  on  an 
immense  scale  naphthol,  the  phenol  of  naphthalin.  In  this  method 
pure  benzol,  free  from  thiophene,  is  placed  with  about  five  times  its 
weight  of  strongest  commercial  sulphuric  acid  (670  B.)  in  closed 
cast-iron  pots,  provided  with  stirrers  and  lead  coolers  and  capable 
of  being  heated  by  a  steam  jacket.  While  the  mixture  is  slowly 
stirred,  the  vessel  is  gently  heated  with  steam  in  such  a  manner  that 
the  vapors  of  benzol  which  pass  into  the  cooler  are  continually 
returned  to  the  kettle.  After  a  number  of  hours  the  reaction  is 
finished,  and  the  benzol  not  acted  on,  is  collected  as  it  flows  from 
the  cooler.  The  crude  benzol-sulphonic  acid,  mixed  with  the  excess 
of  sulphuric  acid  used,  is  allowed  to  cool  and  then  diluted  with 
water  in  a  lead-lined  tank.  Slaked  lime  is  added  to  the  hot  solu- 
tion in  sufficient  quantity  until  it  is  faintly  alkaline.  This  removes 
the  excess  of  acid  by  forming  calcium  sulphate,  which  is  then  filtered 
(569) 
