4  Adulterations  of  Essential  Oils.      { A^uaryPi9oim* 
diminution  of  volume  is  generally  proportional  to  the  amount  of 
adulterant.    Glycerin  can  be  used  in  place  of  water. 
In  order  to  positively  establish  the  presence  of  any  of  the  above, 
fractional  distillation  must  be  resorted  to  and  the  substance  finally 
identified  by  means  of  the  iodoform  reaction,  boiling  point,  etc. 
CHEAPER  ESSENTIAL  OILS. 
Turpentine  generally  introduces  abnormalities,  lower  specific 
gravity,  diminished  solubility,  lower  boiling  temperatures  and  dis- 
turbed optical  rotation.  The  latter  can  easily  be  remedied  by  mixing 
the  proper  proportions  of  dextrogyrate  and  lsevogyrate  turpentines. 
Before  a  positive  opinion  can  be  given  relative  to  the  presence  of 
added  turpentine,  in  many  cases  a  careful  comparison  must  be  made 
and  the  characteristic  derivatives  of  pinene  isolated. 
Cedatwood,  copaiba  and  gutjun  balsam  oils  are  generally  indi- 
cated by  their  lesser  solubilities,  higher  specific  gravities  and  opti- 
cal rotations,  but  the  two  latter  can  readily  be  adjusted  by  the 
proper  kind  and  amount  of  turpentine. 
Mineral  oils  (petroleum,  kerosene,  etc.)  are  generally  revealed  by 
their  insolubility  and  indifference  to  the  action  of  strong  acids  and 
alkalies.  They  may  be  variously  isolated,  by  their  insolubilities, 
polymerizing  the  oil  with  concentrated  sulphuric  acid  and  then  dis- 
tilling the  mixture  with  aqueous  vapor,  or  by  oxidizing  with  fuming 
nitric  acid  and  then  removing  the  oxidized  portion  with  hot  water, 
thus  leaving  the  unaffected  petroleum  behind. 
DETERMINATION  OF  PHYSICAL  PROPERTIES. 
The  specific  gravity  is  one  of  the  best  known  properties  of  oils  and 
is  the  one  most  generally  applied  because  it  is  readily  determined. 
The  specific  gravity  is  a  very  important  factor,  but  is  readily  tam- 
pered with,  consequently  very  careful  deductions  based  on  it  must 
be  made. 
Solubility  Very  definite  and  satisfactory  data  have  been  estab- 
lished for  many  oils  relative  to  their  solubility  ;  so  much  so  that 
this  physical  property  is  probably  more  reliable  than  any  other  single 
one.  The  common  adulterants  are  generally  revealed  by  the  applica- 
tion of  this  test.  The  volatile  oils  are  quite  readily  soluble  in  alcohol, 
ether,  acetone,  acetic  ether,  glacial  acetic  acid,  carbon  disulphide, 
chloroform,  benzol,  petroleum  ether  and  paraffin  oil. 
