Am.  Tour.  Pharm. ) 
Dec.  1875.  J 
Japanese  Peppermint  Camphor. 
551 
ride,  the  distillate  (separated  from  the  aqueous  portion)  being  then  poured 
back  and  cohobated  with  the  zinc  chloride  for  some  hours  ;  but  little 
resin  was  thus  formed,  almost  the  whole  being  transformed  into  men- 
thene  boiling  at  164*5  ^^S^'S  (corrected)  after  cohobation  with  so- 
dium (Oppenheim  gives  163°  as  the  B.  P.  of  menthene) ;  on  analysis 
numbers  were  obtained  agreeing  well  with  the  formula  C^QH^g. 
Oppenheim  has  already  shown  that  by  the  addition  of  two  equiva- 
lents of  bromine  to  menthene  a  dibromide  is  formed  which  readily  splits 
up  into  a  terpene  and  hydrobromic  acid,  thus — 
C„H^,Br,=2  HBr+C,„H,, 
and  hence  has  established  a  connection  between  the  terpene  series  of 
hydrocarbons  and  derivatives  of  ethylene  homologues  such  as  C^^H^g 
Br2  (derived  from  C^qHjq  by  substitution  of  of  Br2)  ;  since  terpenes 
have  been  shown  to  be  cymene  derivatives,  it  seems  probable  that 
menthene  is  really  connected  with  cymene;  that  this  is  so  we  have 
found  to  be  the  case  by  combining  four  equivalents  of  bromine  with 
menthene,  and  heating  the  resulting  oily  tetra-bromide  of  menthene,  or 
ietra  hromo  decane^  when  it  breaks  up  into  cymene  and  hydrobromic 
acid,  thus — 
^ioHi8B^4=4HBr+C^oHi4 
Hence  it  is  manifest  that  menthene  is  strictly  intermediate  between  the 
paraffin  and  the  benzene  homologous  hydrocarbons,  as  it  is  between  the 
ethlene  series  and  the  terpenes  ;  and  that  it  is  possible  to  pass  from  the 
paraffin  series  to  the  benzene  series  hy  one  single  simple  reaction. 
The  cymene  thus  obtained  from  menthene  was  found  to  be  identical 
with  ordinary  cymene  obtainable  from  camphor  terpene,  and  various 
constituents  of  essential  oils  as  described  in  the  "Year-Book,"  1863, 
pp.  518,  519  ;  1864,  631. 
The  liquid  Japanese  camphor  oil,  received  from  Mr.  Moss,  appeared 
to  be  a  solution  of  the  solid  camphor  Q^^^O  in  a  permanently  fluid 
substance  containing  less  hydrogen,  probably  indicated  by  the  formula 
C^oH^gO,  and  isomeric  or  identical  with  the  substance  of  that  compo- 
sition contained  in  citronella  oil.  On  fractional  distillation,  a  little 
came  over  below  205°  ;  the  principal  portion,  however,  distilled 
between  210°  and  215°,  and  gave  on  analysis,  numbers  agreeing  with  a 
mixture  of  C^qH2oO  and  C^^H^gO  ;  a  little  came  over  at  higher  temper- 
ature still,  whilst  a  small  portion  was  not  volatile  even  at  300°. 
On  heating  the  distillate  at  210° — 215°  with  zinc  chloride,  men- 
thene was  obtained  boiling  at  165°  together  with  resinoid  substances  de- 
