132  Detection  of  Castor  Oil  in  Copaiba.  {Am'^\^^ 
benzin,  and  the  solutions  remained  clear  and  free  from  sediment  after 
standing  for  several  days  and  even  weeks.  Mr.  Chas.  A.  Bowman, 
however,  informed  me  that  with  larger  quantities  of  the  benzin,  a 
separation  of  the  castor  oil  from  the  copaiba  could  be  effected,  and  that 
capaiba  alone  would  yield  with  sufficient  petroleum  benzin  a  turbid 
mixture  from  which  a  flocculent  precipitate  would  subside. 
On  dissolving  a  pure  copaiba  in  petroleum  benzin,  it  was  found  that 
with  eight  measures  of  the  latter  the  solution  was  perfectly  transparent. 
On  the  addition  of  another  measure  of  benzin,  a  slight  turbidity 
occurred,  which  increased  with  more  benzin,  but  it  took  nearly  a  week 
before  the  liquid  became  clear  again,  depositing  at  the  same  time  some 
transparent  resinous  matter.  When  the  same  copaiba  had  been  pre- 
viously mixed  with  castor  oil,  it  required  the  same  amount  of  petroleum 
benzin  to  produce  a  turbid  solution,  from  which,  in  the  course  of  twelve 
hours,  an  oily  liquid  had  settled  to  the  bottom,  equal  in  bulk  to  the 
castor  oil  employed.  But  in  the  course  of  several  days  the  lower 
layer,  containing  the  castor  oil,  had  increased  to  more  than  double  the 
volume. 
It  appears  from  this  that  petroleum  benzin  may  be  used  for  the 
purpose  indicated,  if  not  less  than  ten  volumes  are  employed,  instead  of 
three,  as  originally  proposed  by  Prof.  Wayne.  But  it  must  not  be 
overlooked  that  pure  copaiba  will  also  produce  a  turbid,  though  less 
opaque  solution,  and  its  separation  and  the  examination  of  the  lower 
layer  may  become  necessary,  unless  a  sufficient  quantity  of  the  castor 
oil,  to  be  remunerative  to  the  sophisticator,  had  been  added,  in  which 
case  the  dense  milkiness  will  at  once  indicate  it. 
Different  kinds  of  copaiba  will  be  found  to  be  of  somewhat  different 
behavior.  A  sample  has  been  handled  by  Mr.  Bowman,  which,  with 
six  volumes  of  the  benzin,  became  turbid  and  readily  separated  floccules, 
while  another,  as  stated  before,  acquired  its  maximum  turbidness  with 
ten  measures  of  benzin,  and  slowly  deposited  a  transparent  resin  \ 
another  kind,  a  Para  copaiba,  over  16  years  old,  required  fifteen  meas- 
ures of  benzin  before  a  slight  turbidity  was  produced,  and  even  after 
it  had  been  mixed  with  its  own  bulk  of  castor  oil,  the  amount  of 
benzin  mentioned  did  not  disturb  it  to  a  very  appreciable  extent* 
Professor  Wayne,  having  operated  with  a  sample  from  which  the  castor 
oil  was  separated  by  three  measures  of  petroleum  benzin,  it  is  evident 
that  the  variations  are  very  considerable,  and  it  is  not  impossible  that 
still  greater  ones  may  be  observed  with  other  kinds  of  copaiba. 
