ESSENTIAL  OIL  CP  VALERIAN". 
139 
had  already  demonstrated  the  pre-existence  of  valerianic  acid 
in  fresh  valerian  root,  and  had  shown  the  uselessness  of  the 
means  recommended  for  developing  it  in  the  oil  extracted  from 
the  plant.  He  has  since  examined  the  oil  to  discover  what 
principles  it  contains,  and  to  establish  by  new  experiments  that 
not  one  of  them  is  capable  of  becoming  transformed  into  valeri- 
anic acid. 
The  oil  of  valerian  has  been  made  the  subject  of  investigation 
by  several  chemists.  Among  others,  Grote,  who  discovered 
valerianic  acid  ;  Ettling  and  Kraps,  who  supposed  it  to  have 
the  same  composition  as  oil  of  turpentine ;  Gerhardt  and  Ca- 
hours,  who  detected  in  it  an  oxygenated  oil  and  a  hydrocarbon. 
Lastly,  in  the  seventh  volume  of  the  Annates  de  Chimie  et  de 
Physique,  1843,  Gerhardt  published  an  important  article  on 
the  subject,  and  his  conclusions  have  been  generally  adopted  in 
all  recent  works  on  chemistry.  In  this  remarkable  work,  the 
author  points  out  some  capital  errors. 
As  well  as  the  acid,  some  chemists  have  denied  the  pre-exist- 
ence of  the  oil  in  the  plant.  According  to  the  partisans  of  this 
opinion,  the  oil  is  formed  secondarily  in  the  same  way  as  oil 
of  bitter  almonds.  Some  experimenters  allowing  the  free  access 
of  air,  evidently  could  not  obtain  the  volatile  principle.  M. 
Bouchardat  having  distilled  the  tincture  of  the  dried  root,  found 
neither  oil  nor  acid.  The  root  exhausted  by  alcohol,  treated 
again  with  water,  and  again  distilled,  furnished  none  ;  and  hence 
the  learned  professor  concluded  that,  as  these  principles  had  not 
passed  over  with  the  alcohol  in  which  they  were  soluble,  and 
could  not  be  found  in  the  water,  they  did  not  exist  in  the  plant. 
The  fallacy  of  the  first  experiment  is  seen  at  once.  Alcohol 
is  entirely  evaporated  at  78°  C,  while  the  acid  in  solution  re- 
quires 110°,  and  the  oil  120°  degrees  ;  and  therefore  the  alcohol 
passes  over  leaving  these  bodies  in  the  residue,  where  they  must 
be  sought  for. 
That  the  oil  does  pre-exist  in  the  plant  is  proved  by  the 
following  experiments : — 
If  one  of  the  radicles  is  simply  crushed  on  a  piece  of  white 
bibulous  paper,  an  oily  spot  is  produced. 
The  distillation  of  the  fresh  root  with  water  gives  an  oil  vary- 
ing in  color,  according  to  the  sort  of  plant  used.    It  is  green 
