Am.  Jour  Pharm.") 
Feb.,  1884.  / 
Benzoic  Acid  from  Urine. 
97 
must  be  kept  moist.  It  will  be  seen  from  these  tests  that  all  the 
Pharmacopoeias  require  that  benzoic  acid  must  be  prepared  from  gum 
benzoin.  The  German  Pharmacopoeia  directs  that  it  is  to  be  made  by 
sublimation,  have  a  yellowish-brown  color,  aromatic  odor,  and  contain 
a,  substance  (styrol?)  capable  of  reducing  potassium  permanganate. 
Hence  the  benzoic  acid  of  the  German  Pharmacopoeia  is  not  intended 
to  be  chemically  pure.  The  United  States  Pharmacopoeia  indicates 
that  it  should  be  prepared  by  the  lime  method  and  be  chemically  pure. 
Urine-benzoic  acid  can  never  answer  to  the  tests  for  the  former,  but 
when  prepared  by  the  method  above  described,  it  will  be  seen  that  it 
comes  up  to  the  standard  imposed  by  the  tests  for  the  latter. 
The  following  table  shows  how  five  specimens  of  benzoic  acid  com- 
pare with  each  other: 
Urine  benzoic  acid 
unsublimed. 
Urine  benzoic  acid 
sublimed. 
Benzoic    acid  ex- 
tracted with  lime 
from  Palembaug 
gum. 
A  commercial  speci- 
men   of  benzoic 
acid. 
Benzoic   acid  sub- 
limed   from  Pe- 
nang  gum. 
Solut'n  in  cold  H2S04 
when  warmed  is  
Dark  brown 
Lightbrown 
Lightbrown 
Lightbrown 
Dark  brown. 
Mixed    with  moist 
CuO  gives  in  the 
No  green 
No  green 
No  green 
No  green 
No  green 
tinge. 
tinge. 
tinge. 
tinge. 
tinge. 
Warmed  with  solu- 
tion   of  K2Mn208 
No  odor. 
No  odor. 
No  odor. 
No  odor. 
Smell  of  oil 
of  bitter 
A  cold  solution  with 
almonds. 
K2Mn208  becomes... 
Colo  r less 
Not  color- 
Not color- 
Not color- 
Colorless in  5 
in  5  min- 
less in  12 
less  in  12 
less  in  12 
minutes. 
utes. 
hours. 
hours. 
hours. 
Crystallizes  from  an 
aqueous  solution  in 
Pri  smatic 
Flaky  crys- 
Flaky crys- 
Flaky crys- 
Small needles 
needles. 
tals. 
tals. 
tals 
Odor  
Like  urine. 
Faintly  aro- 
Faintly aro- 
Disagree- 
Strongly  aro- 
matic. 
matic. 
ably  aro- 
matic. 
matic. 
It  would  appear  then  that  benzoic  acid  prepared  from  hippuric  acid 
is  totally  unfit  for  use  in  medicine,  unless  it  has  been  sublimed.  When 
sublimed  its  character  is  entirely  changed.  Instead  of  crystallizing 
from  water  in  large  prisms,  it  does  so  in  flaky  crystals  like  the  natural 
varieties.  It  has  lost  its  offensive  smell  and  has  even  a  faint  aromatic 
odor.  It  is  purer  than  the  acid  obtained  by  direct  sublimation  of  the 
gum,  for  it  does  not  contain  any  volatile  hydrocarbons,  and  solution  of 
7 
