AmA&87h7£:rm-}    Detection  of  Castor  Oil  in  Copaiba.  1 8 1 
fixed  oils,  especially  castor  oil.  The  "  British  Pharmacopoeia  "  fur- 
nishes a  qualitative  method  of  examination,  but  the  tests  are,  in  prac- 
tice, totally  insufficient,  as  the  exact  degree  of  rectification  of  the- 
benzol  (an  important  point)  is  not  stated,  and  the  difference  between  a 
pure  balsam  stain  and  that  with  a  small  percentage  of  oil  is  very  slight, 
unless  the  two  are  observed  side  by  side.  The  other  methods  which 
have  been  proposed  may  be  summarized  as  follows  : 
1.  Pure  balsam  gives  a  translucent  and  nor  an  opaque  emulsion,  with, 
strong  solution  of  ammonia. 
2.  Pure  balsam,  if  boiled  with  water  for  some  hours,  leaves  a  tena- 
cious resin. 
3.  The  specific  gravity. 
The  latter  test  is  entirely  fallacious,  owing  to  the  great  variation  \m 
commercial  samples,  and  the  others,  though  possibly  characteristic  with) 
large  admixtures,  fail  with  anything  under  20  per  cent. 
Observing  the  close  affinity  between  copaivic  and  pinic  acids,  it 
struck  me  that  advantage  might  be  taken  of  the  difference  of  solubility 
of  the  sodium  soaps  in  certain  menstrua.  A  very  good  solvent  for 
sodium  pinate  has  been  discovered  by  M.  Barfoed  to  be  a  mixture  of 
five  parts,  by  volume,  of  absolute  ether,  and  one  part  absolute  alcohoL, 
which,  moreover,  only  dissolves  sodium  oleate  to  an  exact  extent,  cor- 
responding to  1  in  1000  of  oleic  acid.  I  will  not  occupy  space  by 
detailing,  at  length,  the  numerous  experiments  on  a  great  number  o& 
samples  of  balsam,  varying  in  age  and  color,  from  every  known  com- 
mercial source,  but  the  whole  thing  ended  in  the  certain  conclusion) 
that  besides  the  essential  oil  (which  is  dissipated  in  the  process  of 
analysis)  good  commercial  balsam  contains  only  copaivic  acid,  which* 
forms  a  sodium  salt,  instantly  soluble  in  the  ether-alcohol  mixture,  and: 
a  little  altered  resin  not  so  readily  saponifiable,  forming  a  salt  only 
slowly  soluble.  The  amount  of  this  second  resin  I  have  found  to 
vary  slightly,  and,  in  very  old  samples,  especially  of  Maranham  bal- 
sam, may  sometimes  amount  to  5  per  cent.,  although  usually  really 
less.  Going  upon  the  principle  that  performing  any  official  analysis 
the  lowest  commercial  standard  should  be  taken,  I  have  adopted  six 
per  cent,  as  the  highest  possible  quantity  of  the  second  resin  ever 
existing  in  any  sample  of  balsam  still  having  a  trace  of  odor  remaining. 
