DETECTION  OF  ADULTERATED  ESSENTIAL  OILS.  339 
J  vol.  oil  of  juniper,  -  = —  2°*985 
J  vol.  oil  of  turpentine,       == — 36°*568 
1  vol.  mixture,  -       =— 39°-553 
From  this  it  is  proved  that  the  quantity  of  the  adulterating 
oil  of  turpentine  can  be  detected  through  the  medium  of  the 
saccharimeter.  But  if  the  essential  oil  is  adulterated  not  only 
with  oil  of  turpentine  but  also  with  another  optically  active  oil, 
the  saccharimeter  test  is  of  no  value.  In  order  to  find  out  the 
quantity  of  the  adulterating  oil  of  turpentine  from  the  deviation 
showed  by  the  oil  of  turpentine,  by  the  adulterated  oil,  and  by 
the  mixture,  the  numbers  of  deviation  have  to  be  brought  in 
reference  to  a  common  distinct  starting  point.  This  starting 
point  generally  is  the  power  of  rotation,  that  is  the  deviation  of 
the  respective  oil  as  calculated  for  a  tube  of  100mm  length,  and  a 
specific  gravity  of  1.  This  power  of  rotation,  the  worth  of  which 
is  generally  expressed  by  [oc  ],  is  the  following  for : 
Oil  of  turpentine,  [oc  ]  =— 42°-275 
Oil  of  lemon,  -  [oc  ]  =+ 80° -573 
Oil  of  juniper,     -       [oc  ]  =—  39479 
The  quantity  of  oil  of  turpentine  employed  for  the  adultera- 
tion is  calculated  as  follows  : 
a  the  power  of  rotation  of  the  pure  oil. 
b  "       "     "      "       "  "    oil  of  turpentine. 
c  "       "     "      "       "  "  mixture. 
m  "    quantity  "  u  " 
«  "  "  "    adulterating  oil  of  turpentine. 
The  quantity  of  the  pure  oil  as  contained  in  the  mixture  is 
—m — a,  and  the  power  of  rotation  of  this  quantity  is=(m  x)a; 
the  power  of  rotation  of  the  oil  of  turpentine  — — b  x,  and  the 
power  of  rotation  of  the  whole  quantity  of  mixture  =m  o;  hence 
results  the  following  equation  : 
(m — x)a — b  x  =m  c 
m  a — a  x — b  x=rn  c 
m  a — m  c=a  x-\-b  x 
m(a — c) 
 ~x 
a+b 
