140  ESSENTIAL  OIL  OF  VALERIAN. 
when  obtained  from  the  wild  valerian,  and  yellow  when  got 
from  the  cultivated  plant.  From  whichever  obtained,  however, 
its  characters  do  not  sensibly  differ  in  other  respects.  It  is  very 
fluid,  and  gives  off  a  strong  penetrating  odor  like  that  of  the 
root ;  its  taste  is  disagreeable,  and  a  little  sour  ;  its  specific 
gravity  at  10°  C.=  0-936.  It  reddens  litmus  paper  strongly. 
Exposure  to  the  air  removes  the  greater  part  of  its  hydro-carbon, 
and  some  of  the  valerianic  acid  and  water  it  contains ;  at  the 
same  time  the  oxygenated  oil  thickens  and  is  converted  into  a 
green  resin. 
The  oil  boils  at  200°  C.  A  temperature  of  — 40°  does  not 
congeal  it ;  but  about  — 1509  white  flocculi  form,  and  rise  to 
the  surface,  which,  when  removed,  change  to  an  oily  liquid, 
having  the  odor  of  valerianic  acid,  of  which  the  flocculi  are  com- 
posed. 
The  oil  of  valerian  does  not  combine  with  either  caustic 
potassa  or  soda. 
Cold  nitric  acid  colors  it  blue ;  if  the  mixture  be  slightly 
heated,  nitrous  vapors  are  disengaged,  and  at  the  same  time  the 
oil  is  changed  into  a  blue  resin,  which  is  heavier  than  water, 
soluble  in  ether,  insoluble  in  alcohol  and  caustic  potassa,  agree- 
ing in  these  respects  with  the  resin  obtained  by  distilling  the 
oil,  and  that  extracted  from  the  dried  root. 
When  submitted  to  a  simple  distillation,  the  fresh  oil  gives  at 
from  120°  to  200p  C.  a  yellow,  oily,  limpid,  transparent  liquid, 
which  is  only  the  oil  a  little  impaired  by  the  operation.  This 
product  contains  nearly  all  the  acid  of  the  oil ;  its  color  becomes 
deeper  by  keeping. 
If  the  heat  be  raised  to  from  200°  to  300°,  a  limpid  trans- 
parent oil  of  a  bottle-green  color  is  obtained,  which  is  sensibly 
acid.  Exposure  to  the  air,  as  well  as  excessive  distillations, 
transforms  it  into  a  green  resin  ;  nitric  acid,  on  the  contrary, 
converts  it  into  a  blue  resin. 
If,  after  removing  the  product  of  this  second  fractionation, 
the  heat  be  continued  to  from  300^  to  400°,  a  thick,  oily, 
opaque  substance  of  a  greenish  color  passes  over,  containing 
traces  of  acid.  This  is  completely  changed  into  resin  of  valerian 
by  the  action  of  nitric  acid. 
The  two  last  products,  green  and  blue,  mixed  and  distilled 
