Amju0ne?if93arm*}  Notes  on  Essential  Otis.  307 
gravity  and  the  rotatory  power.  The  alcohol  test  requires  to  be  made 
more  stringent — the  oil  should  dissolve  at  200  C,  in  from  1-5  to  2 
volumes  of  80  per  cent,  alcohol.  Slight  turbidity,  increasing  on 
addition  of  more  alcohol,  is  due  to  separation  of  bergaptene ; 
but  no  drops  of  oil  should  remain  undissolved.  Distillation  of  the 
oil  under  normal  atmospheric  conditions  causes  considerable  decom- 
position, and  this  treatment  is  quite  useless  for  the  purpose  of  valua- 
tion. The  results  of  a  long  series  of  experiments  have  proved 
that  oil  containing  a  high  amount  of  ester  is  distinguishable  from 
those  kinds  containing  smaller  amounts  by  the  higher  specific  gravity 
and  greater  solubility  in  alcohol  of  80  per  cent.  Oil  of  undoubted 
purity,  pressed  by  Messrs.  Schimmel,  was  found  to  contain  more 
ester  than  any  other  kind,  and  it  is  probable  that  a  perfectly  pure 
oil  is  not  to  be  met  with  in  commerce.  Experiments  with  mixtures 
of  bergamot  oil  and  turpentine,  orange  or  lemon  oils,  have  shown 
that  the  ester  determinations  may  be  fully  relied  upon,  and  as  a 
minimum  amount  there  should  be  38  per  cent.  The  specific  gravity- 
should  not  be  under  0*881  at  150  C,  and  the  optical  rotation  not- 
more  than  20°  with  a  column  of  100  mm.  Practical  experience  has 
long  proved  that  distillation  of  the  oil  is  injurious,  and  that  the 
much  less  convenient  process  of  pressing  must  be  preferred  on  that 
account.  Experiments  have  shown  that  distilled  oil  contains  much 
linalool,  as  a  consequence  of  the  decomposition  of  the  ester,  and 
by  acetylating  a  distilled  oil  containing  only  12  per  cent,  of  ester 
the  amount  of  ester  was  increased  to  61-5  per  cent.  Even  pressed 
bergamot  oil  contains  some  linalool,  and  a  sample  containing  37 
per  cent,  ester  was  found  after  acetylation  to  contain  47  per  cent, 
ester.  It  may  probably  be  assumed  that  the  oil  obtained  by  dis- 
tilling the  residue  of  the  pressing  operation  is  used  for  adulterating 
the  pressed  oil,  and  that  would  account  for  the  frequently  small1 
amount  of  ester,  as  well  as  the  low  specific  gravity  of  the  com- 
mercial oil  as  compared  with  absolutely  pure  pressed  oil. 
Lemon  Oil — As  the  general  result  of  further  investigation,  it  has 
been  found  desirable  to  apply  tests  of  increased  stringency  in  judg- 
ing of  the  purity  of  this  oil.  The  determinations  of  optical  rotation 
and  specific  gravity  are  of  special  importance  ;  since  the  admixture 
of  turpentine  oil — almost  the  only  adulterant — has  the  effect  of 
reducing  the  rotatory  power  and  increasing  the  specific  gravity.  By 
comparison  of  a  number  of  samples  with  oil  of  known  purity, 
