638  Chemistry  of  Clove  Oil.  { A£fer?«™- 
V   THE  CHEMISTRY  OF  CLOVE  OIL1 
Erdmann  has  published  some  interesting  results  of  his  investi- 
gation of  clove  oil  and  the  oil  distilled  from  clove  stalks.  In  pre- 
paring caryophyllene  by  treating  clove  oil  with  solution  of  caustic 
alkali,  the  undissolved  portion  of  the  oil  was  always  found  to  be 
oxygenated,  and  only  by  using  alcoholic  potash  was  it  obtained  free 
from  oxygen.  Oil  from  clove  stalks  shaken  with  dilute  caustic 
alkali  yielded  at  once  the  sesquiterpene. 
On  treating  the  oil  that  is  separated  from  clove  oil  by  solution  of 
caustic  alkali,  with  alcoholic  potash,  and  adding  some  ether  to  dis- 
solve and  separate  the  terpene,  the  alkaline  solution  was  found  to 
contain  eugenol,  which  was  separated  on  acidifying  with  sulphuric 
acid,  and  on  distilling  the  acidified  liquid,  acetic  acid  was  obtained. 
Hence  it  was  evident  that  clove  oil  contains,  as  one  of  its  constitu- 
ents, aceteugenol,  a  compound  which  is  at  once  saponified  by  alco- 
holic potash,  but  less  readily  by  a  water  solution  of  caustic  alkali, 
and  thus  the  presence  of  oxygen  in  the  oil  undissolved  by  caustic 
alkali  solution  was  accounted  for,  as  well  as  the  circumstance  that 
neither  this  undissolved  oil  nor  clove  oil  itself  has  a  constant  boil- 
ing point.  That  is  not  due  to  difference  in  the  amount  of  caryo- 
phyllene ;  for  though  it  has  a  somewhat  higher  boiling  point  than 
eugenol,  the  tension  of  both  substances  is  nearly  the  same  at  1230  C, 
under  a  pressure  of  13  millimetres,  and  the  higher  boiling-point, 
1250  to  1500  C,  of  the  oil  undissolved  by  caustic  alkali  is  due  to 
the  presence  of  aceteugenol. 
In  the  determination  of  eugenol  in  clove  oil  by  Thorns'  method,* 
it  is  assumed  that  the  whole  of  the  eugenol  is  present  in  the  free 
state,  and  the  question  arose  whether  the  presence  of  some  portion 
of  it  in  the  state  of  ester  affected  the  determination.  That  was 
found  to  be  the  case  by  comparative  experiments  with  clove  oil  pre- 
viously saponified  by  heating  to  ioo°  C,  with  caustic  alkali,  and 
with  oil  which  had  not  been  so  treated,  the  results  given  by  three 
samples  being  as  follows  : 
Thorns.  Total  eugenol. 
Clove  oil,  A   .     83*9  85*68 
Clove  oil,  B  ,  .  |f2'97 
1 8277  84-84 
Clove  oil,  C   80-2  81*9 
1  Jour.  Prakt,  Chetn.,  I/VL,  175,  through  Pharmaceutical  Journal,  November 
6,  1897. 
2  Pharmaceutical  Journal,  (3),  XXII,  450. 
