Am.  Jour.  Pharm. 
April,  1894. 
Salicylic  Acid  in  Food. 
193 
as  this  method  involved  the  use  of  metallic  sodium  the  product  was 
expensive. 
After  securing  the  entire  success  of  his  second  process  in  1874, 
Kolbe  turned  his  attention  to  finding  uses  for  his  product.  In  that 
and  the  succeeding  year  he  published  a  number  of  papers  on  its  use 
as  a  food  preservative,  as  did  several  of  his  pupils  and  assistants, 
etc.  Public  attention  became  attracted  to  the  acid,  and  its  use  as  a 
preservative  spread  with  great  rapidity.  In  1877  the  French 
Government  found  itself  obliged  to  take  official  action  regarding 
the  use  in  wine  of  salicylic  acid. 
Analytical  chemists  of  course  were  not  slow  to  recognize  the  new 
demand  on  their  skill  involved  by  the  use  of  this  substance  as  an 
addition  to  food,  and  methods  for  its  detection  were  soon  elaborated. 
The  number  of  these  methods  has  yearly  increased,  and  at  present 
a  fair  sized  bibliography  of  analytical  literature  relative  to  salicylic 
acid  might  be  compiled. 
The  most  useful  properties  of  salicylic  acid,  analytically  speaking, 
are  that  it  is  volatile  with  steam  ;  that  it  is  extracted  from  acid 
liquids  by  ether,  chloroform,  carbon  bisulphide  or  benzol;  that  it 
gives  a  bright  purple  color  with  ferric  chloride,  a  green  color  with 
copper  acetate,  and  a  rose  color  when  boiled  with  Millon's  solution, 
and  that  when  converted  into  the  methyl  ester  it  gives  rise  to  a 
characteristic  odor  of  wintergreen.  The  iron  test  is  the  one  which 
is  universally  used  for  the  final  recognition  of  this  substance,  the 
previous  separation  from  the  food  being  made  either  with  one  of 
the  solvents  above  named  or  by  distillation.  It  is  extremely  deli- 
cate, giving  a  good  reaction  with  a  tenth  milligram  in  twenty-five 
cc.  of  liquid.  The  copper  test  is  not  particularly  delicate,  nor  is  the 
methyl  ester  test,  at  lease  as  far  as  I  am  concerned.  This  latter  test 
has  been  brought  forward  particularly  by  Dr.  Curtman,  of  St.  Louis. 
The  test  with  Millon's  solution  is  given  by  other  substances  extract- 
able  from  foods  by  ether.  The  iron  test  is  not  given  by  any  sub- 
stance occurring  in  foods  and  extracted  by  ether  to  my  knowledge. 
Carbolic  acid  gives  the  reaction  nearest  approaching  it  in  color  of 
the  common  substances,  but  this  substance  does  not  occur  in  food. 
Tannic  acid,  a  little  of  which  is  sometimes  taken  up  by  ether  from 
wines,  gives  a  blackish  or  greenish  color  which  has  a  tendency  to 
hide  the  salicylic  color. 
In  the  laboratory  of  the  Department  of  Agriculture  the  method 
