608 
Exain  illation  of  Bdlxdia  of  Peru. 
( Am.  Jour.  Pharm. 
I      Dec,  1882. 
addition  of  15  per  cent,  of  benzoin  solntion  to  Pern  balsam,  specific 
gravity  1-146,  lowered  the  specific  gravity  to  1*135.  The  author  pre- 
fers to  use  the  pycnometer  in  determining  the  specific  gravity  of  the 
balsam.  The  plan  recommended  by  Hager,  of  observing  whether  a 
drop  of  balsam  floats  or  sinks  in  a  saline  solution  of  known  density, 
he  considers  to  be  defective,  as  the  behavior  of  the  drop  is  affected  by 
the  conditions  under  which  it  reaches  the  surface  of  the  solution. 
The  author  does  not  consider  that  the  estimation  of  the  free  acid 
constitutes  such  a  good  criterion  as  the  sj)ecific  gravity.  The  five  gen- 
uine samples  of  Peru  balsam  required  from  O'l  to  7-2  per  cent,  of  soda 
crystals  for  their  exact  neutralizatiou.  The  purified  storax  corres- 
ponded to  4*5  to  5*1  ])er  cent.  ;  the  copaiba  balsam  to  5*1  per  cent. ; 
the  colophony  solution  to  7*5  per  cent.;  the  benzoin  solution  to  14  per 
cent,  of  soda;  only  the  castor  oil  was  devoid  of  free  acid.  The  esti- 
mation of  free  acid  would  therefore  only  be  of  use  in  conjunction  with 
other  tests,  chiefly  in  the  determination  of  admixture  with  benzoin  or 
castor  oil,  the  former  increasing  and  the  latter  diminishing  the  acidity. 
A.  Behavior  of  Balsam  of  Peru  towards  Solvents.— [1).  Spirit  of 
wine  dissolves  half  its  weight  of  Peru  balsam  almost  clear ;  a  further 
addition  of  spirit,  however,  renders  the  solution  turbid,  through  sepa- 
ration of  a  small  quantity  of  resin.  Ether  behaves  similarly ;  it  mixes 
clear  with  an  equal  quantity  of  balsam,  but  the  solution  becomes  tur- 
bid uj)on  the  addition  of  more  ether,  resin  separating  equal  to  about  6 
per  cent,  of  the  Peru  balsam. 
As  ether  and  alcohol  easily  form  clear  solutions  with  both  castor  oil 
and  the  colophony  solution,  they  do  not  furnish  a  means  for  detecting 
admixtures  of  these  substances.  Purified  storax  and  copaiba  balsam 
give  with  alcohol  very  turbid  and  with  ether  clear  solutions ;  benzoin 
solution  mixes  clear  with  alcohol,  and  turbid  with  ether,-  about  10  per 
cent  of  resin  separating.  Consequently  these  solvents  give  no  decisive 
indication  of  adulteration  of  Peru  balsam  with  the  last  three  substances. 
(2).  Carbon  bisulphide  dissolves  Peru  balsam  with  the  exception  of 
11  to  16  per  cent,  of  resin,  which  adheres  so  fast  to  the  sides  of  the 
vessel  that  the  light  colored  solution  can  be  poured  off  clear.  Benzoin 
resin  is  almost  insoluble  in  carbon  bisulphide,  giving  up  only  the  ben- 
zoic acid  present,  so  that  carbon  bisulphide  furnishes  a  good  means  for 
detecting  a  large  admixture  of  benzoin.  The  following  table  shows 
the  behavior  of  one  part  of  the  substance  tested  in  two  parts  of  carbon 
bisulphide. 
