THE  AMERICAN 
JOURNAL  OF  PHARMACY. 
APRIL,  1887. 
ESSENTIAL  OIL  PAPERS. 
By  Albert  M.  Todd. 
1.    The  Polariscope  as  a  Revealer  of  Adulterations. 
During  the  month  of  February  last,  being  the  guest  of  S.  P. 
Duffield,  M.  D.,  Ph.  D.,  of  Dearborn,  Michigan,  with  whom  I  was 
associated  in  conducting  some  analyses  of  spurious  oil  of  peppermint., 
in  behalf  of  our  State,  my  attention  was  called  by  that  gentleman  to  a 
Mitscherlich  polariscope  of  especial  fine  construction,  made  by  Desaga,, 
of  Heidelberg,  and  brought  to  this  country  many  years  ago,  when  the 
doctor  returned  from  studying  with  Liebig.  That  this  instrument  as 
an  investigator  of  essential  oils  is  so  little  known  and  understood, 
seems  marvelous.  The  standard  and  official  books  to  which  we  refer 
(pharmacopoeias  and  dispensatories)  are  entirely  silent  as  to  the  polar- 
izing test  on  many  essential  oils ;  and  when  it  is  mentioned,  give  only 
the  fact  as  to  the  oil  being  dextrogyre — polarizing  to  the  right,  or  l^evo- 
gyre — polarizing  to  the  left,  the  angles  of  polarization,  which  are  ot 
most  vital  importance  not  being  referred  to. 
The  reason  of  this  deficiency  is  probably  due  to  the  fact  that  the- 
authors  of  our  scientific  books  have  not  had  the  facilities  for  distilling 
personally  the  oils  under  examination ;  and  finding  wide  variations^ 
owing  to  impurities,  not  having  certain  knowledge  which  was  pure 
and  which  not,  they  were  unable  to  lay  down  the  limits  with  sufficient 
closeness. 
The  immediate  cause  of  our  associated  analyses  was  the  confirmation 
of  some  tests  which  I  had  hastily  made  in  court  regarding  some  adul- 
terated essential  oils  which  had  been  sold  to  a  large  extent,  the  inferior 
quality  of  which  had  been  supposed  to  be  entirely  due  to  dementho- 
lization — the  oil  showing  that  test ;  but  which  I  found  to  be  chiefly 
attributable  to  adulteration  with  refuse  oil  of  camphor.    The  oils  in 
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