io6 
Cineol  in  Oil  of  Eucalyptus. 
<  Am.  Jour.  Pharm. 
1     March,  1915. 
The  determination  of  cineol  in  cineol-bearing  oils  by  means  of 
arsenic  acid  is  carried  out  as  follows : 
Deliver  from  a  pipette  10  Cc.  of  the  oil  into  a  glass  dish  (pref- 
erably a  round-bottom  one)  of  50  Cc.  capacity,  which  is  imbedded 
in  finely  cracked  ice.  Add  10  Cc.  of  concentrated  arsenic  acid 
(containing  about  85  per  cent,  arsenic  acid;  see  ":  Xote  "  below)  and 
stir  until  precipitation  is  complete.  When  the  mixture  ceases  to 
congeal  further,  allow  to  stand  ten  minutes  in  the  ice.  At  this 
point,  if  the  mixture  forms  a  hard  mass,  indicating  an  oil  rich  in 
cineol,  5  Cc.  of  purified  petroleum  ether  should  be  added,  and  the 
mass  mixed  well ;  transfer  immediately  to  a  hardened  filter  paper2 
by  means  of  a  pliable  horn  spatula;  spread  evenly  over  the  surface 
of  the  paper  and  lay  a  second  hardened  filter  paper  over  the  top. 
Outside  of  the  hardened  filters  place  several  thicknesses  of  ab- 
sorbent or  filter  paper,  and  transfer  the  whole  to  an  ordinary  letter 
press,  bringing  to  bear  all  the  pressure  possible  for  about  one  minute. 
Change  the  outside  absorbent  papers  and  press  again,  repeating  the 
operation,  if  necessary,  until  the  cineol  arsenate  is  apparently  dry 
and  separates  readily  when  touched  with  a  spatula.  The  pressing  is 
not  complete  when  a  hard  mass  remains  which  is  broken  up  with 
difficulty ;  the  method  usually  requires  two  changes  of  filter  paper, 
pressing  each  time  for  about  two  minutes;  if  left  too  long  in  the 
press  the  compound  may  decompose.  Xow  transfer  completely  the 
compound  by  means  of  the  horn  spatula  to  a  glass  funnel  inserted 
into  a  100-Cc.  cassia  flask  with  neck  measuring  10  Cc.  graduated 
in  1/10  Cc.  Wash  the  precipitate  into  the  flask  with  a  stream  of 
hot  water  from  a  wash  bottle,  assisting  the  disintegration  with  a 
glass  rod.  Place  the  flask  in  boiling  water  and  rotate  until  the 
compound  is  thoroughly  broken  up ;  add  enough  water  to  cause  the 
cineol  to  rise  into  the  neck  of  the  flask,  cool  to  room  temperature, 
and  read  oft  the  volume;  on  multiplying  the  latter  by  10  the  per- 
centage of  cineol  in  the  oil  is  obtained. 
In  judging  whether  or  not  petroleum  ether  should  be  added,  the 
following  rule  should  be  observed :  Add  enough  petroleum  ether  to 
soften  the  cineol  arsenate  so  as  to  obtain  a  plastic  mass ;  the  quantity 
necessary  never  exceeds  5  Cc,  and  decreases  with  oils  containing  less 
than  80  per  cent,  of  cineol.    The  object  of  adding  petroleum  ether 
2  In  our  work  we  found  most  useful  Schleicher  &  Schull's  hardened  niters 
No.  575>  18^2  cm.  diameter. 
