io4 
Cine o I  in  Oil  of  Eucalyptus. 
JAm.  Jour.  Pharm. 
"I     March,  1915. 
Semi-annual  Report,  for  April,  1913,  p.  62,  containing  results  of 
experiments  on  known  mixtures  of  cineol  with  pinene,  which,  when 
estimated  by  this  method,  showed  a  cineol  content  of  95  per  cent. ; 
a  mixture  of  50  per  cent,  cineol  and  50  per  cent  terpineol,  on  the 
other  hand,  yielded  only  30  per  cent,  cineol.  Time  does  not  permit 
us  to  enter  into  a  more  complete  discussion  of  these  results. 
4.  Resorcinol  Method,  or,  more  correct,  Resorcinol  Methods, 
since  there  is  an  "  original  "  method  as  described  in  Schimmel  &  Co.'s 
Report  for  October,  1907,  in  Gildemeister  &  Hoffmann's  "  Volatile 
Oils,"  1913,  p.  601,  and  as  proposed  for  the  inclusion  in  the  Ninth 
Revision  of  the  U.  S.  Pharmacopoeia,  and  also  a  "  Modified  Resor- 
cinol Method  "  as  given  in  Schimmel  &  Co.'s  Report  for  April, 
1908. 
The  "  original  "  method  is  based  on  the  fact  that  cineol  forms 
an  addition  produced  with  resorcinol,  which  is  soluble  in  an  excess 
of  concentrated  resorcinol  solution. 
The  process  is  carried  out  as  follows :  "  To  10  Cc.  of  oil  con- 
tained in  a  100  Cc.  cassia  flask  enough  50  per  cent,  resorcinol  solu- 
tion is  added  to  fill  the  flask  about  four-fifths.  For  five  minutes 
the  mixture  is  thoroughly  shaken,  and  the  portion  of  the  oil  which 
has  not  gone  into  solution  is  driven  into  the  neck  with  resorcinol 
solution.  Any  oily  particles  adhering  to  the  walls  of  the  flask  are 
caused  to  rise  to  the  surface  by  rotating  the  flask  or  gently  tapping 
it.  After  the  resorcinol  solution  has  become  perfectly  clear,  which 
usually  requires  several  hours,  the  volume  of  oil  remaining  is  read 
off,  the  cineol  content  ascertained  by  subtracting  this  amount  from 
10,  and  the  resultant  multiplied  with  10  in  order  to  obtain  the  per- 
centage by  volume.  Oils  very  rich  in  cineol  are  advantageously 
diluted  with  an  equal  volume  of  turpentine  oil,  since  the  cineol- 
resorcinol  occasionally  crystallizes  from  concentrated  solution^  thus 
rendering  futile  the  entire  process." 
It  soon  became  apparent,  however,  that  this  method  gave  too 
high  results,  for  the  reason  that  constituents  of  eucalyptus,  other 
than  cineol,  are  also  soluble  in  the  resorcinol  solution,  and  further 
investigation  of  the  subject  led  to  the  "  Modified  Resorcinol  Method," 
which  consists  in  distilling  the  oil  of  eucalyptus  at  such  a  rate  that 
only  one  drop  distils  over  in  one  second,  collecting  the  portion  dis- 
tilling between  1700  and  1900  C,  and  subjecting  this  portion  to  the 
estimation  by  the  above-described  resorcinol  method. 
