A  oiober^1"-}     Notes  on  Estimating  Eucalyptol.  493 
method  valueless  for  quantitative  work.  It  is  with  the  latter  that 
the  writer's  experience  coincides.  For  estimating  eucalyptol  the 
method  is  unsatisfactory,  but  as  a  means  for  detecting  the  presence 
of  eucalyptol  in  the  oil,  it  is  of  much  service.  This  is  good  so  far 
as  it  goes,  but  the  all- essential,  how  much,  is  lacking. 
The  writer  has  made  some  experiments  along  another  line  that  may 
be  of  interest.  The  eucalyptol  phosphate  is  obtained  by  cooling  the 
oil  in  ice-water,  gradually  adding  half  its  volume  of  phosphoric  acid, 
with  agitation,  cautiously  keeping  cool.  The  contents  of  the  beaker 
can  readily  be  kept  cool  as  follows :  Add  the  acid  to  the  oil,  cool 
the  mixture  in  ice-water,  then  slowly  agitate  with  a  glass  rod  until 
uniformity  results.  After  preparing  the  eucalyptol  phosphate,  it  is 
purified  between  folds  of  filter  paper  by  means  of  heavy  pressure. 
This  portion  of  the  work  having  been  well  done,  the  solid  mass 
ought  to  consist  of  eucalyptol,  phosphoric  acid  and  traces  of  water 
and  oil  constituents,  aside  from  eucalyptol.  By  weighing  this  addi- 
tion product  we  have  the  combined  amount  of  eucalyptol  and  phos- 
phoric acid.  Now,  by  treating  the  eucalyptol  phosphate  with  hot 
water,  decomposition  results  and  the  phosphoric  acid  can  readily  be 
estimated  by  titrating  with  a  volumetric  solution  of  potassium 
hydroxide.    The  eucalyptol  is  easily  obtained  by  difference. 
The  method  as  executed  by  the  writer,  is  as  follows  :  8  grammes 
of  the  oil  are  weighed  out  in  a  suitable  beaker,  cooled  in  ice  water, 
4  c.c.  of  phosphoric  acid  (1*75)  added  and  again  placed  in  ice-water. 
After  cooling,  the  contents  of  the  beaker  are  slowly  and  thoroughly 
mixed  by  means  of  a  glass  rod,  the  eucalyptol  phosphate  removed, 
purified  by  pressure,  weighed,  decomposed  with  hot  water,  and  the 
acid  estimated  by  means  of  a  standard  alkaline  solution.  Of  course 
it  is  understood  that  smaller  quantities  can  be  worked  with.  It  is 
necessary  to  add  more  of  the  phosphoric  acid  in  some  cases.  This 
is  true  in  the  case  of  pure  eucalyptol.  Twice  the  above  amount 
was  added  for  the  results  obtained  in  this  paper. 
The  result  obtained  by  the  above  process  for  pure  eucalyptol  and 
a  number  of  oils  are  given  in  the  table  below.  Other  data  are  also 
included. 
