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REVIEW  OF  TESTS  FOR  METHYL  SALICYLATE  IN  OILS 
OF  GAULTHERIA  AND  BIRCH.* 
By  Charles  H.  La  Wall,  Ph.M., 
philadelphia,  pa. 
Periodicity  is  one  of  the  commonest  of  natural  phenomena.  Man 
having  caught  the  spirit  of  nature  follows  close  after  in  this  respect, 
hence  the  common  adage  about  history  repeating  itself.  This  is 
particularly  true  of  certain  lines  of  scientific  investigation.  A  par- 
ticular instance  is  that  of  the  tests  for  distinguishing  between  oil 
of  gaultheria,  oil  of  birch  and  methyl  salicylate,  and  of  detecting 
mixtures  of  these  oils,  for  which  a  new  method  is  published  every 
few  years.  The  reason  for  this  search  is  found  in  the  wide  differ- 
ence in  price  and  the  temptation  to  mix  them  or  substitute  one 
for  the  other. 
There  are  certain  fundamental  factors  in  a  problem  of  this  kind 
which  point  to  the  probability  of  a  test  being  devised  for  distinguish- 
ing the  pure  oils,  but  an  equal  improbability  of  any  infallible  method 
being  discovered  of  detecting  admixtures  of  one  with  the  other,  even 
in  large  amounts.    In  support  of  this  belief  let  me  state  my  reasons: 
Without  going  fully  into  the  chemistry  of  the  respective  oils,  it 
will  sufhce  to  say  that  the  differences  between  them  are  essentially 
as  follows: 
(1)  Methyl  salicylate  is  a  distinct  chemical  entity  and  appears 
upon  the  market  as  such  in  a  state  of  high  purity. 
(2)  Oil  of  gaultheria  consists  of  methyl  salicylate  to  the  extent 
of  99  per  cent.,  the  balance  consisting  of  a  parafhn,  an  aldehyde,  a 
ketone,  an  alcohol  and  an  ester. 
(3)  Oil  of  birch  consists  of  methyl  salicylate  to  the  extent  of 
over  99.5  per  cent.,  the  remaining  trace  consisting  of  the  paraffin 
and  ester,  but  not  the  alcohol  nor  aldehyde. 
*  Read  at  the  October  meeting  of  the  Philadelphia  Branch  of  the  A.  Ph.  A. 
