Am.  Jour.  Pharm. 
Dec,  1891. 
Synthetical  Carbolic  Acid. 
57* 
but  as  the  solution  is  hot  it  at  once  decomposes  into  phenol  with 
evolution  of  nitrogen — 
(C6H5N  =  N)2S04  +  2H20  =  2C6H5OH  +  H2S04  +  4N 
Neither  of  these  synthetical  methods  can,  at  the  present  time, 
compete  in  price  with  the  extraction  of  carbolic  acid  directly  from 
the  coal  tar  oils. 
A  good  grade  of  crystal  acid  can  be  purchased  abroad  in  large 
quantities  at  this  time  at  about  eleven  cents  per  pound,  while  the 
pure  benzol  used  in  the  first  method  is  worth  at  the  English  refiner- 
ies about  fourteen  cents  per  pound  and  aniline  oil  about  twenty 
cents,  without  taking  into  consideration  the  other  expensive  chemi- 
cals necessary  to  carry  out  the  reaction. 
When  the  synthetical  acid  was  first  placed  upon  the  market  it 
excited  much  interest,  and  purchasers  were  willing  to  pay  the  high 
price  it  commanded,  believing  that  they  were  getting  a  much  purer 
article  than  could  be  produced  by  the  ordinary  methods.  This 
interest  has,  however,  considerably  abated  since  the  acid  has  been 
found  to  redden  just  as  easily  as  the  best  commercial  grades. 
It  could  scarcely  be  expected  that  an  acid  obtained  by  either  ot 
the  complex  reactions  just  described  would  not  be  contaminated  by 
products  formed  by  side  reactions  in  the  process.  In  its  prepara- 
tion by  the  sulphonate  method,  sulphur  compounds  (thiophenols,etc.) 
are  likely  to  be  formed ;  and  its  manufacture  from  a  substance  like 
aniline,  which  so  readily  produces  coloring  matters,  could  scarcely 
be  carried  out  without  at  the  same  time  forming  bodies  which  at 
once,  or  later  under  the  influence  of  light  and  air  would  discolor  it. 
In  addition,  commercially  pure  benzol  or  aniline  oil  always  con- 
tain small  quantities  of,  respectively,  toluol  or  toluidine.  These 
bodies  being  submitted  to  the  same  treatment  as  their  homologues 
give  cresylic  acid.  It  is  true  that  this  acid  would  be  present  only 
in  minute  quantities,  but  sufficient  to  reduce  the  melting  point  of  the 
resulting  carbolic  acid. 
Lunge  has  shown  that  the  addition  of  1-3  per  cent,  of  cresylic 
acid  to  pure  phenol  reduces  the  melting  point  eight  degrees  to  323^  °, 
and  in  the  preparation  of  a  high  grade  carbolic  acid  a  difference 
of  a  part  of  a  degree  is  of  great  importance. 
Forty  degrees  acid  is  at  present  a  commercial  article  sold  at 
excessively  low  prices,  and  if  a  small  part  of  the  attention  and  labor 
