338  DETECTION  OF  ADULTERATED  ESSENTIAL  OILS. 
particularly  those  belonging  to  the  camphenes,  the  carbon  of 
which  is  in  the  proportion  of  5  to  8  to  their  hydrogen,  have  an 
action  on  the  polarized  light,  deviating  the  light  either  to  the 
right  or  the  left  hand  side.  These  optical  researches  have  been 
made  by  Biot,  Soubeiran,  Capitaine,  Gladstone  and  Berthelot,  in 
order  to  establish  the  constitution  of  the  camphenes.  I  made 
some  researches  to  detect  the  adulteration  of  the  essential  oil 
with  the  oil  of  turpentine. 
For  that  purpose,  a  chemically  pure  oil  of  lemon  which  I  had 
prepared  myself,  was  tested  in  a  saccharimeter,  the  tube  of  which 
was  200mm  long. 
The  deviation  was  -f  137° -296  for  the  middle  yellow  ray.  The 
oil  of  turpentine  used  for  the  research,  prepared  by  myself,  had 
a  specific  gravity  of  0*865  and  gave  a  deviation  of  — 73° -135. 
A  mixture  of  equal  volumes  of  both  these  oils  showed  a  devia- 
tion of  -f-30° -65.  The  calculation  gives  a  deviation  of  +32o,081 
in  the  following  manner : 
|  vol.  oil  of  lemon,  -  =  +  68-648 
J  vol.  oil  of  turpentine,        = — 36*567 
1  vol.  mixture,  -  =+32°-081 
A  mixture  of  2  vol.  oil  of  lemon  with  one  vol.  oil  of  turpen- 
tine gave  a  deviation  of  +65° -34;  from  the  calculation  results  a 
deviation  of  -j-67°*152,  as  follows  : 
§  vol.  oil  of  lemon,  -  =+91°-531 
i  vol.  oil  of  turpentine,      =— 24°-379 
1  vol.  mixture  -  =+67°-152 
I  made  the  same  researches  with  pure  oil  of  juniper,  which  I 
had  prepared  myself,  and  arrived  at  the  following  results : 
The  oil  used  for  the  experiment  had  a  specific  gravity  of 
0*858  and  showed  a  deviation  of  — 5° -970.  The  oil  of  turpen- 
tine employed  was  the  same  as  in  the  above  mentioned  experi- 
ment. A  mixture  of  equal  volumes  of  oil  of  juniper  and  oil  of 
turpentine  showed  a  deviation  of  — 40° -84  ;  the  calculation  gives 
a  deviation  of — 39°-553  as  follows: 
