892 
Tests  for  Methyl  Salicylate. 
(  Am.  Jour.  Pharm. 
\     December,  1920. 
It  is  certain  in  the  light  of  the  foregoing  premises  that  any  dis- 
tinguishing tests  must  be  based  upon  differences  due  to  the  traces 
of  associated  substances  in  birch  and  gaultheria  oils,  respectively, 
for  the  methyl  salicylate  factor  is  common  to  all  three  products. 
It  likewise  follows  that  there  is  absolutely  no  hope  of  any  test 
for  detecting  added  methyl  salicylate  in  either  oil  of  birch  or  oil  of 
gaultheria  by  a  positive  reaction  if  the  methyl  salicylate  be  pure 
for  pure  methyl  salicylate  reacts  similarly  whatever  its  origin. 
Any  possibility  of  distinguishing  these  oils,  therefore,  must  be 
based  upon  the  discovery  of  a  test  which  will  identify  these  elusive 
factors  which  are  present  in  scarcely  more  than  traces  in  oils  of 
birch  and  gaultheria,  respectively,  and  to  detect  mixtures  it  would 
be  necessary  to  discover  a  method  which  can  be  transformed  into 
a  quantitative  reaction  or  one  in  which  advantage  can  be  taken  of 
its  intensity. 
The  only  reactions  of  a  distinguishing  nature  likely  to  be  dis- 
covered are  color  reactions,  and  as  color  reactions  are  usually  un- 
certain and  when  translated  into  colorimetric  methods  for  quanti- 
tative use,  are  rarely  very  accurate,  the  chances  of  accomplishing 
anything  of  real  value  in  this  research  are  seen  to  be  very  remote, 
for  it  is  only  of  academic  importance  to  be  able  to  distinguish  the 
products  in  a  state  of  purity  if  mixtures  of  one  with  the  other  cannot 
be  detected  with  certainty. 
From  time  to  time  investigators  have  pursued  this  ignis  fatuus 
of  a  color  reaction  which  should  serve  both  as  a  distinguishing  test 
of  the  pure  substances  and  a  method  of  detecting  admixtures,  com- 
pletely ignoring  the  fallacy  of  such  a  quest. 
In  1 913,  Stanislaus  and  Semmel,  in  the  Proceedings  of  the  Penn- 
sylvania Pharmaceutical  Association,  proposed  several  reagents  for 
accomplishing  this  result.  The  reagents  consisted  of  nitric  acid, 
sulphuric  acid  and  formaldehyde  mixed  in  several  combinations. 
The  resulting  color  reactions  with  the  three  products  were  described 
as  brown,  light  brown  and  yellow;  straw,  light  straw  and  light  yel- 
low; amber,  yellow  and  colorless.  There  is  not  enough  distinctive- 
ness about  tests  giving  such  results  to  make  them  worthy  of  consid- 
eration as  affording  hope  of  detecting  mixtures. 
In  1914,  Watson  and  Sayre,  in  the  /.  A,  Ph.  A.,  p.  1658-9,  pro- 
posed several  tests.  One  was  based  upon  differences  of  color  pro- 
duced in  the  three  products  b)^  sulphuric  acid.  The  reactions 
are  described  as  dark  red,  yellow  or  light  red,  and  colorless  for  oils 
