572  Colorimetric  Estimation  of  Vanillin.  {A%Je0c%P9?arm 
which  is  used  in  producing  a  synthetical  acid  was  expended  in  the 
further  purification  of  this  400  acid,  without  doubt  just  as  good  if 
not  a  purer  article  could  be  produced  direct  from  tar  oils  and  at  a 
very  much  lower  cost. — Laboratory  of  the  H.  W.  Jayne  Chemical 
Company,  Nov.  14,  1891. 
A  COLORIMETRIC  ESTIMATION  OF  VANILLIN. 
By  Frank  X.  Moerk,  Ph.G. 
Contribution  from  the  Chemical  Laboratory  of  the  Philadelphia  College  of  Pharmacy. — 
No.  97. 
Read  at  the  Pharmaceutical  Meeting,  Nov.  17,  189 1. 
"  Will  natural  vanillin  give  the  same  color  reaction  as  the  syntheti- 
cal product  ?"  and  "  Is  this  test  applicable  to  the  assay  of  vanilla 
extracts  ?"  were  questions  asked  of  me  at  the  last  Pharmaceutical 
Meeting  after  reading  a  paper  on  a  new  color  reaction  of  vanillin 
answers  to  these  queries  will  be  given  in  the  following  paper. 
Without  having  any  doubt  that  the  vanillin  of  different  origin 
would  react  similarly,  I  received  from  Mr.  Beringer  a  small  quantity 
of  vanillin  which  had  been  removed  from  the  bean,  and  with  this 
obtained  the  same  reaction,  thus  showing  by  another  test  the 
identity  of  the  natural  and  synthetic  vanillin. 
To  determine  the  applicability  of  this  test  in  examining  vanilla 
extracts  and  their  substitutes,  Mr.  Beringer  prepared  for  me  a  number 
of  mixtures  of  vanillin  and  coumarin,  some  of  which  were  colored 
with  various  vegetable  coloring  substances.  A  pure  extract  of 
vanilla,  largely  diluted  with  water,  will  give  with  salts  of  iron  a 
peculiar  violet-brown  coloration,  which  interferes  notably  with  the 
test,  and  to  remove  this  disturbing  influence  it  is  important  to 
decolorize  the  extract  before  proceeding  with  the  development  of 
the  characteristic  color. 
To  effect  the  decolorization  various  methods  were  tried.  Adding 
lead  nitrate  solution  to  the  diluted  samples,  and  then  by  the  addition 
of  magnesium  oxide,  suspended  in  water,  precipitating  lead  hydrate, 
which  carried  along  with  it  the  coloring  matter ;  it  was  found  that 
by  this  procedure  considerable  of  the  vanillin  was  also  removed 
from  the  solution  (as  much  as  three-fourths  in  some  cases).  Instead 
of  the  lead  salt,  alum  and  ferric  sulphate  were  then  used  with  some- 
what better  results,  but  still  with  loss  of  vanillin ;  agitating  the 
diluted  extract  with  freshly  precipitated  ferric  hydrate  was  not  sue- 
