AmMJa°rch5  *i9i9m'  }  Determination  of  Vanillin  in  Vanilla  Extract.  i6j 
A  NEW  METHOD  FOR  THE  DETERMINATION  OF 
VANILLIN  IN  VANILLA  EXTRACT.1 
By  Arthur  W.  Dox  and  G.  P.  Plaisance, 
CHEMISTRY  SECTION,  IOWA  AGRICULTURAL  EXPERIMENT  STATION. 
The  official  method  for  the  determination  of  vanillin  in  vanilla 
extract  consists  essentially  in  removing  the  alcohol,  extracting  the 
vanillin  with  ether,  crystallizing  it  from  the  ethereal  solution  and 
weighing  it  directly,  identifying  the  crystals  if  necessary  by  their 
melting  point.  This  method  was  first  proposed  by  Hess  and 
Prescott.2 
Modifications  were  subsequently  introduced  by  Winton  and 
Silverman,3  and  by  Winton  and  Bailey.4 
For  details  of  manipulation  reference  should  be  made  to  the 
official  methods  of  the  A.  O.  A.  C.5 
The  whole  operation  is  rather  lengthy  and  tedious. 
Methods  dependent  upon  the  precipitation  of  vanillin  by  various 
reagents  have  been  suggested  but  have  not  come  into  common  use. 
Hanus6  used  m-nitrobenzoylhydrazide  as  a  precipitant,  and  also 
platinic  chloride7  for  estimating  vanillin  in  the  presence  of  piperonal. 
Moulin8  converted  the  vanillin  into  a  yellow  methyl  picrate  and  esti- 
mated it  colorimetrically.  More  recently  Folin  and  Denis9  have 
devised  a  colorimetric  method  based  upon  the  color  obtained  by 
means  of  phosphotungstic  and  phosphomolybdic  acids. 
The  writers10  have  found  that  thiobarbituric  acid  in  the  presence 
of  12  per  cent,  hydrochloric  acid  is  a  general  reagent  for  the  pre- 
cipitation of  aromatic  aldehydes  and  have  applied  it  to  the  quantita- 
tive determination  of  furfural11  Under  these  conditions  vanillin 
gave  with  thiobarbituric  acid  an  insoluble  vermillion  colored  pre- 
1  Reprinted  from  Simmons'  Spice  Mill,  November,  1918. 
2  J.  Am.  Chem.  Soc,  21,  256  and  719,  1899. 
3  Ibid.,  24,  1 128,  1902. 
4  Ibid.,  27,  719,  1905. 
5  Bur.  Chem.  Bull.  No.  152,  p.  146. 
6  Zeitschr.  Untes.  Nahr.  Genussm.,  10,  585,  1905. 
7  Ibid.,  10,  657,  1900. 
8  Bull.  Soc.  Chem.,  29,  278,  1903. 
9  /.  Ind.  Eng.  Chem.,  4,  670,  1912. 
10  Dox  and  Plaisance,  /.  Am.  Chem.  Soc,  38,  2164,  1916. 
11  Dox  and  Plaisance,  ibid.,  38,  2156,  1916. 
