102 
Cineol  in  Oil  of  Eucalyptus. 
f  Am.  Jour.  Pharm. 
\     March,  1915. 
eucalyptus  oils  depend  exclusively  upon  their  content  of  cineol 
(eucalyptol).  Various  methods  proposed  heretofore,  without  ex- 
ception, suffer  from  one  shortcoming — gross  inaccuracy ;  either  due 
to  the  wrong  basis  of  method,  or  to  the  instability  of  those  com- 
pounds which  have  been  suggested  as  serviceable  for  the  separation 
of  cineol. 
To  the  class  of  methods  based  on  wrong  premises  belong  the 
"  Permanganate  Method  ''  proposed  by  Francis  D.  Dodge  (Journal 
Industrial  and  Engineering  Chemistry,  vol.  iv,  August,  1912,  p.  529) 
and  the  "  Resorcinol  Method  "  proposed  by  Schimmel  &  Co.  (Semi- 
annual Report  of  Schimmel  &  Co.,  October,  1907)  ;  the  latter 
method  is  now  slated  for  inclusion  in  the  Ninth  Revision  of  the 
United  States  Pharmacopoeia,  and  it  will  thus  become  responsible 
for  the  admission  into  the  pharmaceutical  practice  of  inferior 
eucalyptus  oils,  as  we  propose  to  show  further  below. 
The  methods  based  on  the  separation  of  unstable  addition  prod- 
ucts of  cineol  are  :  the  phosphoric  acid  method  and  the  hydrobromic 
acid  method. 
The  various  methods  mentioned  will  be  outlined  briefly,  as  it  is 
not  our  purpose  here  to  enter  into  a  thorough  discussion  of  these. 
Exhaustive  information,  both  pro  and  con,  may  be  obtained  from 
the  literature  on  the  subject,  and  especially  by  perusing  the  semi- 
annual reports  of  Schimmel  &  Co. 
1.  Phosphoric  Acid  Method— ■" Introduce  into  a  beaker  a  solu- 
tion prepared  by  dissolving  10  Cc.  of  oil  of  eucalyptus  in  50  Cc.  of 
purified  petroleum  benzin ;  immerse  the  beaker  in  a  freezing  mixture 
and  add  phosphoric  acid,  drop  by  drop,  with  constant  stirring,  until 
the  white  magma  of  cineol  phosphate  formed  begins  to  assume  a 
yellowish  or  pinkish  tint ;  then  transfer  the  magma  to  a  force  filter, 
wash  it  with  cold,  purified  petroleum  benzin,  and  then  dry  it  by 
pressure  between  two  porous  plates.  Transfer  the  precipitate 
(cineol  phosphate)  to  a  narrow  graduated  cylinder,  and  add  warm 
water,  which  will  cause  separation  of  the  cineol.  The  volume,  in 
cubic  centimetres,  of  the  separated  oil,  multiplied  by  10,  represents 
the  volume  per  cent,  of  cineol  (eucalyptol)." 
The  addition  product  of  eucalyptol  with  phosphoric  acid,  as 
obtained  by  this  method,  is  a  semi-solid,  sticky  substance  which  de- 
composes very  readily  and  renders  a  quantitative  separation  very 
difficult,  if  not  altogether  impossible.  In  consequence  of  this,  the 
results  obtained  by  this  method  are  invariably  too  low. 
