io8 
Cineol  in  Oil  of  Eucalyptus. 
i  Am.  Jour.  Pharm. 
\      March,  1915. 
simply  to  testing  known  mixtures  containing  a  higher  percentage  of 
cineol,  we  have  omitted  this  part  of  investigation  from  the  line  of 
our  work  as  originally  planned. 
In  order  to  test  the  applicability  of  our  method  to  various  oils 
containing  cineol,  we  have  collected  from  several  sources  a  number 
of  samples  of  such  oils  and  subjected  them  to  assaying  by  the 
arsenic  acid  method,  comparing  our  results  with  those  obtained  by 
the  resorcinol  method. 
The  comparison  was  carried  out  both  on  original  oils  and  on 
fractions  distilling  over  between  170  and  1900  C.  as  outlined  in 
Schimmel  &  Co.'s  Report,  April,  1908  ("  Modified  Resorcinol 
Method  "). 
For  the  purpose  of  determining  the  purity  of  cineol  separated  by 
the  arsenic  acid  method,  several  portions  of  cineol,  obtained  in  the 
course  of  assays  of  original  oils,  were  mixed  and  subjected  to 
physical  examination  with  the  following  results : 
Specific  gravity  at  25°C,  0.9218;  melting-point,  i°  C. ;  optical  rotation,  +  o°  13  - 
On  the  other  hand,  being  already  familiar  with  the  fact  that  re- 
sults obtained  by  the  resorcinol  method  on  original  oils  are  not 
reliable,  we  examined  only  that  cineol  which  was  obtained  by  the 
"  modified  resorcinol  method,"  and  which  was  thus  subjected  to 
considerable  purification,  at  first  by  distilling  the  oil,  then  by  dis- 
tilling with  steam  the  resorcinol  solution  containing  the  soluble 
portion  of  the  above  distillate.  Cineol  collected  in  this  manner 
from  a  number  of  resorcinol  solutions  possessed  the  following 
properties : 
Specific  gravity  at  25°  C,  0.9242 ;  melting-point,  -30  C. ;  optical  rotation,  +  o°  f 
The  criterion  of  a  pure  cineol,  according  to  the  U.  S.  P.,  being 
specific  gravity  at  250  C.  -  0.921  to  0.923,  melting-point  -  1 0  C, 
and  optically  inactive,  the  purity  of  cineol  obtained  by  the  arsenic 
acid  method,  as  evidenced  by  its  physical  properties,  shows- conclu- 
sively that  none  of  the  constituents  of  oil  of  eucalyptus  other  than 
cineol  are  precipitated  by  the  arsenic  acid,  and  that  the  precipitate 
of  cineol  arsenate  can  be  freed,  with  comparative  ease,  from  the 
non-cineol  portion  of  the  oil  in  question. 
Results  of  assays  made  by  us  on  18'  samples  of  various  oils  are 
incorporated  in  the  following  table: 
