Am.  jou.Pharm.j  ^  ^^^^        Peunywyal  Oil  461 
sp.  gr.  was  stated  as  0.940  to  0.940,  and  the  oil  as  soluble  in  two 
parts,  by  volume,  of  a  mixture  of  alcohol  3  volumes,  water  i  volume 
(approximately  70  per  cent,  alcohol  by  volume).  "This  is  what  is 
known  in  commerce  as  'American  Pennyroyal  Oil.'  "  The  later 
revision  of  the  U.  S.  P.  dismissed  this  title,  and  so  we  have  now  no 
official  standard  for  Oleum  Hedeoma. 
A  large  portion  of  the  Oil  of  Pennyroyal  of  commerce,  however, 
is  of  European  production,  and  is  stated  to  be  distilled  from  Mentha 
pulegium  Linne.  The  European  oil  has  a  sp.  gr.  of  0.930-0.960, 
and  is  soluble  in  two  parts  of  70  per  cent,  alcohol.  Pulegone  is  the 
most  active  constituent  of  both  of  the  commercial  varieties  of  Penny- 
royal Oil,  and  is  present  in  somewhat  larger  proportion  in  the  Euro- 
pean oil.  It  is  a  ketone  CioHieO,  in  which  the  Carbonyl  group,  CO 
unites  with  two,  alcohol  radicals.  Its  boiling  point  is  given  by 
several  authorities  as  from  221°  C.  to  224°  C. 
The  sample  of  oil  under  consideration  was  a  limpid,  pale  yellow 
liquid  having  a  distinct  pennyroyal  odor,  with  a  mint-like  tendency. 
The  sp.  gr.  was  0.884,  ^-iid  it  mixed  clear  in  all  proportions  with  70 
per  cent,  alcohol.  The  low  specific  gravity  and  the  solubility  at 
once  indicated  that  the  sample  was  not  normal. 
10  Cc.  was  fractionally  distilled  from  a  small  distilling  flask, 
5  Cc.  distilled  over  and  was  collected  at  a  temperature  below  85  °  C. 
This  portion  responded  to  the  ethyl  acetate  test  and  other  reactions 
for  ethyl  alcohol,  proving  that  the  sample  was  not  pure  Oil  of  Penny- 
royal, but  a  mixture  of  which  50  per  cent,  was  alcohol. 
The  fraction  distilling  between  218°  C.  and  224°  C.  was  collected, 
as  this  should  contain  the  Pulegone,  the  characteristic  constituent 
of  pennyroyal  oil.  It  measued  1.6  Cc.  corresponding  to  16  per  cent, 
in  the  sample,  or,  possibly,  32  per  cent,  in  the  original  oil.  It  had 
the  unmistakable  odor  of  pennyroyal,  greatly  intensified  and  very 
persistent,  and  was  soluble  in  1.5  parts  of  70  per  cent,  alcohol. 
To  prove  that  this  was  Pulegone,  two  identifying  tests  were 
adopted.  Pulegone  being  a  ketone,  the  iodoform  test  was  applied 
as  a  group  reaction,  and  the  response  was  prompt  with  copious  pro- 
duction of  iodoform.  Pulegone  can  be  reduced  by  nascent  hydrogen 
to  form  a  menthol.  A  small  portion  was  dissolved  in  dehydrated 
alcohol,  metalhc  sodium  added;  after  the  reaction  was  completed 
the  solution  was  diluted  with  water  and  extracted  with  petroleum 
ether.  On  evaporating  the  solvent  the  residue  gave  the  distinct 
odor  and  taste  of  a  menthol.    The  quantity  worked  with  did  not 
