Am.  Jonr.  Pharm. 
April,  1908. 
Benzoic  Acid  in  Catsup. 
THE  QUANTITATIVE  ESTIMATION  OF  BENZOIC  ACID 
IN  CATSUP. 
By  Charges  H.  I^aWau*  and  Henry  A.  Bradshaw. 
The  quantitative  estimation  of  benzoic  acid  in  catsup  has  hitherto 
been  attended  with  some  difficulty  on  account  of  the  fact  that  there 
is  usually  a  great  tendency  to  emulsification,  which  can  be  counter- 
acted only  by  extreme  dilution  of  the  catsup;  also,  the  benzoic  acid, 
being  obtained  by  the  shaking-out  process,  requires  to  be  purified 
by  sublimation.  The  following  process  has  proved  to  be  almost 
free  from  these  defects,  and  work  upon  known  samples  has  given 
repeatedly  concordant  results,  agreeing  within  one  or  two-hundredths 
of  I  per  cent.    It  is  as  follows : 
Catsup,  20  grammes;  sodium  chloride,  2  grammes;  hydrochloric 
acid,  5  c.c. ;  saturated  solution  of  sodium  chloride,  25  c.c.  Shake 
the  mixture  thoroughly  for  about  five  minutes,  transfer  to  a 
moistened  filter  and  collect  the  filtrate  in  a  receiving  vessel  gradu- 
ated to  100  c.c.  Wash  the  residue  upon  the  filter  with  a  saturated 
solution  of  sodium  chloride  until  IOO  c.c.  of  filtrate  have  been 
obtained.  Transfer  the  filtrate  to  a  separatory  funnel  and  shake  out 
with  three  portions  of  chloroform,  using  25  c.c,  15  c.c.  and  10  c.c, 
respectively.  Evaporate  the  chloroform  at  room  temperature.  If 
the  residue  is  perfectly  white  and  crystalline,  as  is  usually  the  case, 
dry  to  constant  weight  over  sulphuric  acid  in  a  desiccator.  If  the 
residue  is  slightly  yellowish  and  oily,  which  rarely  occurs,  dissolve 
it  in  about  10  or  15  c.c.  of  weak  ammonia  water,  filter  into  a  sepa- 
ratory funnel,  washing  the  filter  and  funnel  with  water.  Acidulate 
with  dilute  sulphuric  acid,  and  again  shake  out  with  chloroform. 
The  white,  crystalline  residue  of  benzoic  acid,  as  obtained  by  drying 
in  a  desiccator,  may  be  weighed,  preparatory  to  checking  up  by 
titration. 
After  obtaining  the  weight,  from  3  to  5  c.c.  of  alcohol  are  added 
to  dissolve  the  residue  in  the  capsule  from  which  the  chloroformic 
solution  has  been  evaporated,  a  few  drops  of  phenolphthalein  solu- 
tion are  added,  and  the  solution  is  titrated  with  twentieth  normal 
potassium  hydroxide  solution,  and  the  results  calculated  to  benzoic 
acid.  The  titration  should  agree  with  the  gravimetric  estimation 
very  closely,  the  difference  rarely  being  more  than  1  or  2  milli- 
grammes.   The  solution  resulting  from  the  titration,  which  is  very 
