Am.  Jour.  Pharm.  "> 
March,  1915.  / 
Cineol  in  Oil  of  Eucalyptus. 
103 
2.  The  Hydrobromic  Acid  Method  is  carried  out  as  follows  :  "  In 
a  highly  cooled  solution  (freezing  mixture)  of  10  Cc.-^  eucalyptus 
oil  in  40  Cc.  low-boiling  petroleum  ether  (boiling-point  about  400) 
absolutely  dry  gaseous  hydrobromic  acid  is  introduced  until  a  precipi- 
tate is  no  longer  formed.  The  pure  white  hydrobromide  of  cineol 
formed  is  rapidly  collected  with  a  suction  pump  and  washed  with 
cold  petroleum  ether.  Into  the  filtered-off  liquid  hydrobromic  acid  is 
again  introduced ;  any  precipitate  formed  is  collected  separately,  and 
then  added  to  the  bulk.  For  the  purpose  of  removing  the  petroleum 
ether,  the  cineol  hydrobromide  is  left  standing  for  a  quarter  of  an 
hour  in  a  vacuum;  it  is  then  rinsed  with  a  little  alcohol  into  a 
cassia  flask  and  decomposed  with  water.  The  cineol  separated  off 
is  brought  into  the  neck  of  the  flask  by  the  addition  of  more  water, 
and  the  quantity  of  the  oil  read  oft  the  scale.  By  multiplying  with 
10,  the  cineol  content  of  the  oil  employed  is  obtained  in  per  cent, 
by  volume." 
This  method  has  the  same  drawback  as  the  phosphoric  acid 
method,  namely,  rapid  decomposition  of  the  addition  product.  More- 
over, the  procedure  for  obtaining  the  cineol  hydrobromide  is  a  very 
complicated  one,  and  is  not  suitable,  therefore,  for  ordinary  practical 
purposes. 
3.  The  Potassium  Permanganate  Method  is  based  upon  the  fact 
that,  in  the  cold,  cineol  remains  practically  unattacked  by  potassium 
permanganate,  whereas  the  remaining  constituents  of  the  oils  in 
question  (eucalyptus  oil  and  cajuput  oil)  are  oxidized  into  soluble 
compounds.    The  process  is  carried  out  as  follows :  "  10  Cc.  of  the 
011  under  examination  are  placed  in  a  narrow-necked  flask,  cooled 
with  ice-water,  and  shaken  with  a  gradually  added  5  to  6  per  cent, 
solution  of  potassium  permanganate  until  the  latter  is  present  in 
excess.    The  mixture  is  then  left  standing  in  ice-water  for  from 
12  to  18  hours  with  occasional  shaking,  after  which  the  manganese 
peroxide  which  has  separated  out  is  brought  to  solution  by  means 
of  a  careful  addition  of  sulphurous  acid  (or  sodium  bisulphite  -\- 
hydrochloric  acid).  The  unattacked  oil  (eucalyptol)  is  brought  into 
the  neck  of  the  flask,  pipetted  into  a  graduated  tube,  washed  with  a 
little  alkali,  and  estimated  volumetrically.  Its  specific  gravity 
should  be  0.929  to  0.930  (150)  ;  it  should  be  inactive,  and  dissolve 
in  3.5  volumes  60  per  cent,  alcohol  at  25 °." 
We  have  not  investigated  this  method  personally,  but  are  rather 
willing  to  accept  the  criticism  as  published  in  Schimmel  &  Co.'s 
