AMbeeUi',"i874RM'}  Note  on  Japanese  Oil  of  Peppermint.  579 
Oppenheim  called  the  subject  of  his  experiments,  camphor  or  stea- 
ropten  of  peppermint  oil,  and  also  menthol.  In  Dr.  Attfield's  "Man- 
ual," peppermint  camphor  is  styled,  more  systematically,  I  think, 
hydrous  menthene,  menthene  (C10H18)  being  the  hydrocarbon  which  is 
known  to  be  common  to  several,  if  not  all,  varieties  of  peppermint 
oil.  Oppenheim  found  that  his  camphor  fused  at  36°  C,  and  boiled 
at  210°  C. ;  that  it  was  very  slightly  soluble  in  water,  very  sol- 
uble in  alcohol,  ether,  bisulphide  of  carbon,  fatty  and  essential  oils, 
and  in  alcoholic  solutions  of  the  caustic  alkalies — from  the  soda  solu- 
tion it  crystallized  in  long  needles.  It  was  insoluble  in  aqueous  alka- 
lies. It  liq  uefied  in  a  current  of  hydrochloric  acid  or  of  sulphurous 
acid  gas,  resuming  the  solid  crystalline  character  unchanged  on  ex- 
posure. From  solution  in  strong  acids  it  was  separated  by  water  as 
an  oil,  which  soon  solidified  with  properties  unchanged.  Having 
repeated  these  experiments,  I  have  no  hesitation  in  saying  that  the 
present  specimen,  if  not  the  identical  body  examined  by  Oppenheim^ 
is  a  physical  isomer  of  it ;  for  I  find  that  it  fuses  at  39°  C,  re-solid- 
ifies at  37*5  C,  and  boils  at  215°  C.  It  should  be  stated,  however, 
that  the  boiling  point  remained  stationary  for  some  seconds  at  210° 
0.,  so  that  there  is  the  probability  of  this  specimen  being  a  mixture 
of  Oppenheim's  camphor,  with  a  more  condensed  body  having  higher 
fusing  and  boiling  points.  There  may  be  a  number  of  such  isomers, 
for  Dumas,*  by  exposing  at  0°  C.  American  oil  of  peppermint,  which 
resembles  the  Japan  oil  in  furnishing  crystals  at  a  relatively  high 
temperature,  obtained  crystals  which,  when  purified,  fused  at  25°  C, 
and  boiled  at  208°  C.  In  other  characters  they  resemble  the  crys- 
tals from  Japan  oil.  By  exposing  the  liquid  Japan  oil  to  cold  for 
some  days  (a  great  part  of  the  time  below  0°  C.)  I  failed  to  obtain 
crystals.  It  is  therefore  probable  that  this  oil  has  already  yielded 
such  as  it  is  readily  capable  of  doing.  This  is  indeed  what  one  might 
expect,  for  it  is  not  easy  to  see  the  object  of  sending  both  crystals 
and  liquid  into  the  market,  if  the  original  product  does  not  sponta- 
taneously  deposit  the  former,  and  so  give  an  inconvenient  mixture  of 
solid  and  liquid.  Both  Oppenheim  and  Dumas  concur  in  ascribing 
the  formula  C10II20O  to  the  bodies  they  examined.  Time,  or  the  want 
of  it,  has  not  permitted  me  to  verify  this.  The  menthol  from  spear- 
mint described  by  Gladstone")"  has  the  formula  C10H14O.  It  boils  at 
225°  C.    Oppenheim  considers,  on  very  good  grounds,  that  the  body 
*  Gerhardt,  "Traite  de  Chemie  Organique,"  iv,  357. 
t  Journ.  Chem.  Soc,  24,  10. 
