THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
NOVEMBER,  i8qi. 
A  NEW  COLOR  REACTION  FOR  VANILLIN. 
By  Frank  X.  Moerk,  Ph.G. 
Contribution  from  the  Chemical  Laboratory  of  the  Philadelphia  College  of  Pharmacy, 
No.  95. 
Read  at  the  Pharmaceutical  Meeting  of  the  Philadelphia  College  of  Pharmacy,  October 
20,  1891. 
In  the  various  reference  books  on  organic  chemistry,  there  is  to 
be  found  especially  one  color  reaction  for  vanillin,  namely,  a  violet- 
blue  color,  with  ferric  chloride. 
Some  time  ago,  I  had  occasion  to  examine  a  vanilla  substitute 
which  proved  to  be  a  mixture  of  vanillin  and  coumarin  and  experi- 
enced some  difficulty  in  obtaining  the  above  color  reaction,  caused 
by  using  too  much  ferric  chloride  solution,  and  this  solution  con- 
taining free  hydrochloric  acid;  by  using  a  very  dilute  solution  of 
ferric  chloride  containing  no  free  hydrochloric  acid,  the  test  succeeded 
with  vanillin  solutions  1  :  2,000,  in  which  dilution  a  faint  but  notice- 
able violet-blue  color  results. 
Thinking  that  the  test  could  be  made  more  easily  by  using  a  fer- 
rous solution  and  oxidizing  this  with  bromine  water,  I  was  surprised 
at  the  intense  bluish-green  color  resulting.  The  method  of  apply- 
ing the  test  was  to  add  to  the  aqueous  vanillin  solution  a  few  drops 
of  a  1  percent,  ferrous  sulphate  solution  and  then  the  bromine  water, 
drop  by  drop ;  in  very  dilute  vanillin  solutions  a  single  drop  of  bro- 
mine water  is  sufficient,  in  more  concentrated  solutions  the  color 
deepens  with  the  addition  of  more  bromine  water  until  the  maximum 
intensity  is  reached,  when  more  bromine  water  causes  a  yellowish 
clearing  of  the  bluish-green  test.    If  the  bromine  water  be  added 
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