Am.  Jour.  Pharm. 
May,  1908. 
Oil  of  Bergamot. 
207 
Solubility. — Bergamot  oil  is  soluble  in  one-fourth  to  one-half  vol- 
ume of  90  per- cent,  alcohol,  and  the  solution  does  not  become  turbid 
on  the  addition  of  more  alcohol.  An  accurate  determination  of  the 
solubility  in  alcohol  by  the  above  method  is  out  of  the  question  ; 
the  solubility  can,  however,  be  determined  by  a  method  suggested 
by  the  writer  {Chem.  and  Drug.,  53,  g58).  The  method  is  applica- 
ble to  all  volatile  oils  and  has  the  following  advantages  :  (1)  Only 
one  strength  of  alcohol  is  necessary ;  (2)  the  results  represent  the 
actual  solubility,  and  (3)  they  are  directly  comparable.  5  c.c.  (ac- 
curately measured)  of  oil  are  mixed  with  10  c.c.  of  alcohol  (S.  G. 
799  at  1 5  5°  C),  and  water  is  run  in  from  a  burette,  drop  by  drop, 
until  the  solution  becomes  turbid.  The  number  of  c.c.  of  water 
required  to  produce  turbidity  is  multiplied  by  100,  the  result  being 
termed  the  "  solubility  value." 
The  oils  which  we  have  examined  had  solubility  values  varying 
from  220  to  290.  Turpentine,  lemon  oil,  orange  oil,  citrene  and 
fatty  oils  lower  the  solubility  value. 
Residue. — Bergamot  oil  leaves  a  residue  on  evaporation,  which 
consists  of  bergaptene  (Gildemeister  &  Hoffmann).  The  non-volatile 
residue  is  present  to  the  extent  of  475  to  6  per  cent.  (Schimmel, 
Report,  April-May,  1905).  Fatty  oils  increase  the  residue,  while 
distilled  bergamot  oil,  lemon  oil,  orange  oil,  citrene  and  turpentine 
decrease  the  residue.  We  have  found  4-3  per  cent,  to  6  4  per  cent, 
of  residue  in  pure  oils. 
The  residue  may  be  determined  as  follows:  Take  a  small  porce- 
lain basin  about  2^  inches  in  diameter,  introduce  a  few  grammes  of 
sand,  and  in  the  sand  place  a  small  porcelain  crucible.  The  appli- 
ance is  dried  at  ioo°  C.  and  weighed.  Five  grammes  of  oil  are 
weighed  into  the  crucible  and  the  oil  driven  off  by  heating  to  about 
iod°  C.  The  residue  is  weighed  as  soon  as  all  odor  of  bergamot 
'oil  has  disappeared.  The  above  apparatus  is  used  to  prevent  the 
oil  creeping  over  the  edge  of  the  basin. 
Linalyl  Acetate. — Linalyl  acetate  is  the  most  important  constituent 
of  bergamot  oil,  and  the  value  of  the  oil  depends  on  the  amount 
present.  It  is  determined  by  saponification.  According  to  Schim- 
mel (Report,  April-May,  1905),  the  linalyl  acetate  content  varies  from 
34  to  40  per  cent.  The  oil  obtained  from  unripe  fruit  yields  less  ester 
(down  to  30  per  cent.)  than  that  obtained  from  ripe  fruit.  An  oil 
containing  30  per  cent,  of  ester  must,  however,  be  looked  upon  with 
