Am  M0ay",i?93anu-}  Adulteration  of  Castor  and  Olive  Oils.  233 
thin  layer  adhering  to  the  side  is  examined.  Under  these  condi- 
tions the  samples  were  extremely  fluorescent.  Finally,  a  few  drops 
of  each  sample  were  dissolved  in  carbon  bisulphide  and  treated  with 
stannous  bromide,  with  slight  excess  of  bromine.  In  every  case  a 
fine  coloration,  from  deep  red  to  rich  purple,  was  obtained,  pure 
castor  oil  yielding  little  or  no  color.  Thus  every  single  sample  was 
clearly  proved  to  be  adulterated  with  rosin  oil.  By  adding  abso- 
lute alcohol  in  the  proportion  of  2  parts  to  1  of  oil  a  large  por- 
tion of  rosin  oil  separated  out,  and  by  treatment  with  slaked  lime 
most  of  the  rosin  oil  combined  loosely  with  the  alkali,  and  the  castor 
oil  when  filtered  off  from  the  lime  compound  had  a  specific  gravity 
of  -9665.  By  separating  the  rosin  oil  out  by  the  addition  of  alcohol 
its  specific  gravity  can  be  taken,  and  the  percentage  of  rosin  oil 
approximately  calculated.  However,  we  found  that  saponification 
of  the  oil  with  alcoholic  potash,  evaporating,  to  drive  off  the  alcohol, 
and  extracting  the  unsaponifiable  matter  with  ether,  was  the  most 
direct  method  of  ascertaining  the  proportion  of  rosin  oil,  which  we 
found  to  range  from  35  to  40  per  cent. 
Before  passing  on  to  the  samples  of  impure  olive  oil,  it  will  be 
as  well  to  review  the  results  which  are  obtained  from  the  genuine 
oil. 
The  specific  gravity  is  one  of  the  most  important  features  in 
enabling  one  to  judge  of  the  quality  of  the  oil  to  be  examined.  Of 
many  genuine  samples  examined  by  us  the  specific  gravity  at  I5'5° 
C.  (6o°  F.)  compared  with  water  at  the  same  temperature  never 
exceeded  '917.  In  fact,  we  have  never  found  so  high  a  gravity. 
Low  densities  have  been  observed,  but  -914  is  the  lowest  we  have 
come  across,  and  the  sample  having  this  density  contained  a  con- 
siderable amount  of  free  acid.  The  general  adulterants  of  olive  oil 
are  cotton-seed,  poppy-seed,  arachis,  sesame,  rape  and  hydrocarbon 
oils.  The  addition  of  any  of  these  oils  except  rape  and  the  lighter 
hydrocarbons  would  tend  to  increase  the  density.  The  saponi- 
fication equivalent  is  not  of  much  value  in  assisting  us  to  detect 
the  adulteration  in  the  oils,  the  saponification  numbers  of  the  oils 
generally  used  for  sophisticating  olive  oil  being  nearly  the  same  as 
those  of  the  pure  oil.  If  the  adulterant  were  a  hydrocarbon  oil,  or 
one  from  a  cruciferous  plant,  the  test  would  be  of  great  value,  as  in 
these  cases  the  saponification  equivalent  would  be  sensibly  higher 
than  those  found  for  pure  olive  oil. 
