ESSENTIAL  OIL  OF  LEMOX'S. 
445 
and  to  leave  the  water  in  the  bottle  ;  a  mucilaginous  preparation 
forms  on  the  top  of  the  water,  and  acquires  a  certain  tenacity,  so 
that  the  oil  may  be  poured  off  to  nearly  the  last,  without  disturb- 
ing the  deposit.  Perhaps  cold  water  would  answer  equally  well, 
were  it  carefully  agitated  with  the  oil  and  allowed  some  time  to 
settle.  A  consideration  of  its  origin  and  constitution,  indeed, 
strengthens  this  opinion  ;  for  although  ol.  limonis  is  made  both  by 
distillation  and  expression,  that  which  is  usually  found  in  commerce 
is  made  by  removing  the  "  flavedo  "  of  lemons  with  a  rasp  and 
afterwards  expressing  it  in  a  hair  sack,  allowing  the  filtrate  to 
stand,  that  it  may  deposite  some  of  its  impurities,  decanting  and 
filtering.  Thus  obtained  it  still  contains  a  certain  amount  of  mu- 
cilaginous matter,  which  undergoes  spontaneous  decomposition,  and 
thus  (acting  in  short,  as  a  ferment)  accelerates  a  similar  change  in 
the  oil  itself.  If  this  view  of  its  decomposition  be  a  correct  one, 
we  evidently,  in  removing  this  matter  by  means  of  the  water,  get 
rid  of  a  great  source  of  alteration,  and  attain  the  same  result  as  we 
should  by  distillation,  without  its  waste  or  deterioration  in  flavor. 
I  am,  however,  aware  that  some  consider  the  deposit  to  be  modi- 
fied resin.*  Some  curious  experiments  of  Saussure  have  shown 
that  volatile  oils  absorb  oxygen  immediately  they  have  been  drawn 
from  the  plant,  and  are  partially  converted  into  a  resin,  which  re- 
mains dissolved  in  the  remainder  of  the  essence. 
He  remarked  that  this  property  of  absorbing  oxygen  gradually 
increases,  until  a  maximum  is  attained,  and  again  diminishes  after 
a  certain  lapse  of  time.  In  the  oil  of  lavender  this  maximum  re- 
mained only  seven  days,  during  each  of  which  it  absorbed  seven 
times  its  volume  of  oxygen.  In  the  oil  of  lemons  the  maximum  was 
not  attained  until  at  the  end  of  the  month  ;  it  then  lasted  twenty- 
six  days,  during  each  of  which  it  absorbed  twice  its  volume  of  oxy- 
gen. The  oil  of  turpentine  did  not  attain  the  maximum  for  five 
months,  it  then  remained  for  one  month,  during  which  time  it  ab- 
sorbed daily  its  own  volume  of  oxygen. 
It  is  the  resin  formed  by  the  absorption  of  oxygen,  and  remain- 
*  The  deposit  is  nearly  insoluble  in  water,  is  acid  and  astringent  to  the 
taste,  and  gives  an  acid  reaction  with  litmus.  Spirit  of  wine  dissolves  out  a 
small  portion,  which,  on  evaporation,  h  aves  a  thick  oleo-resinous  substance, 
having  a  rancid  smell.  Ether  leaves  a  pleasant  smelling  resin,  somewhat 
resembling  camphor.  The  remainder  is  nsarly  insoluble  in  liq.  ammonias, 
liq.  potassse,  more  soluble  in  nitric  acid,  and  well  deserves  to  be  further  ex- 
amined. 
