574 
Analysis  of  Essential  Oils. 
f  Am.  Jour.  Pharm. 
I  December,  lt>99. 
presence  of  esters  and  lactones,  about  5  grammes  of  the  oil  are 
boiled  for  an  hour  in  a  reflux  condenser  with  50  c.c.  of  a  semi-nor- 
mal solution  of  alcoholic  alkali ;  subsequent  titration  with  standard- 
ized sulphuric  acid  shows  if  hereby  alkali  has  been  neutralized.  In 
the  case  of  a  positive  result  it  is  almost  indispensable  to  saponify 
the  whole  oil  before  proceeding  any  farther",  because  some  esters, 
like^those  of  linalool,  geraniol  or  terpineol,  will  not  stand  higher 
temperatures  without  being  split,  more  or  less,  into  terpenes  and 
acids,  the  latter  then  effecting  further  chemical  changes,  isomerizing 
and  resinifying  terpenes,  splitting  off  water  from  terpene  alcohols 
and  so  on.  It  must,  however,  not  be  forgotten  that  by  a  prolonged 
action  of  alcoholic  alkali  in  the  heat,  also  some  constituents  without 
acid  character  are  liable  to  undergo  changes  ;  linalool  is  partly 
destroyed  with  formation  of  acids,  allyl  groups  are  isomerized  to 
propenyl  groups  (thus,  for  instance,  safrol,  methyl  chavicol,  apiol  form 
the  corresponding  iso-  compounds).  The  amount  of  alkali  to  be  used 
should,  therefore,  be  calculated  from  the  result  of  the  previous 
quantitative  experiment,  and  any  considerable  excess  carefully 
avoided.  Heating  on  the  water-bath  for  about  half  an  hour  will 
generally  be  found  sufficient  for  a  complete  saponification.  The 
alcohol  is  hereafter  distilled  off  on  the  water-bath  and  the  rest  still 
remaining  in  the  oil  blown  out  with  steam.  From  the  distillate 
some  of  the  more  volatile  parts  of  the  oil  are  obtainable  by  rectifi- 
cation and  washing  with  water. 
The  aqueous  solution  from  the  saponification  (which  should  still 
be  slightly  alkaline)  is  then  separated  from  the  oil,  the  latter  washed 
with  water  and  the  combined  watery  liquids  which,  especially  when 
containing  phenols,  still  hold  some  oil  in  solution,  extracted  with 
ether  or  distilled  with  steam.  The  remaining  solution  then  contains 
the  alkali  salts  of  acids  and  phenols,  also  those  of  oxyacids,  if  lac- 
tones had  been  present. 
To  separate  these  groups,  an  excess  of  dilute  sulphuric  acid  is 
added  and  the  mixture  boiled  for  some  time  in  a  reflux  condenser, 
whereby  the  oxyacids  again  form  lactones.  After  cooling,  the 
whole  is  extracted  with  ether ;  the  ethereal  solution  then  gives  off 
its  phenols  and  acids  when  shaken  with  cold  diluted  caustic  alkali, 
while  the  lactones  remain  behind  on  evaporating  the  ether.  Phenols 
and  acids  are  then  separated  according  to  the  rules  given  above. 
Now  the  number  of  group  reactions,  which  lead  to  the  separation 
