THE  PROCESS  OF  PERCOLATION  OR  DISPLACEMENT.  359 
purpose  of  properly  dividing  them  so  as  to  be  acted  upon  uni- 
formly by  the  menstruum,  and  facilitating  the  process. 
Frequently,  in  compound  preparations  wherein  these  sub- 
stances may  enter,  the  necessity  is  supplied  by  the  other  ingre- 
dients of  the  compound.  Sand,  which  is  usually  recommended, 
does  not  appear  to  be  quite  the  thing  needed  ;  something  of  a 
penetrable  character  more  in  unison  with  the  substance  itself,  is 
what  is  required,  and  oft-times  we  may  have  something  at  hand 
which  will  supply  this  want — poppy  capsules  in  powder,  for  in- 
stance, will  answer  well  for  opium  ;  and,  with  a  view  to  economy, 
the  residue  of  ginger,  in  the  preparation  of  fluid  extract  or  tinc- 
ture, which  by  this  process  is  completely  exhausted,  leaving  no- 
thing behind  but  woody  fibre,  starch,  and  other  inert  matter, 
may  be  reserved  for  mingling  with  the  resins  and  gum-resins. 
The  idea  has  sometimes  occurred  to  me  that  it  would  not  be  out 
of  place  to  prepare  for  this  purpose,  as  a  general  resort,  fine 
sawdust,  by  treating  it  with  alcohol  and  water  to  remove  all 
soluble  matter— the  alcohol  used  in  this  treatment  being  appro- 
priated to  some  suitable  use.  Fortunately  the  substances  re- 
quiring this  sort  of  management  are  few. 
The  conditions,  then,  on  which  I  conceive  depend  the  success 
of  the  displacement  process,  may  be  stated  to  consist,  1st,  in 
the  substance  being  uniformly  and  finely  divided,  prepared  by 
contusion,  and  sifting  through  sieves  ranging  in  fineness  from 
forty  to  sixty  meshes  to  the  linear  inch  ;  2d,  the  dampening  of 
the  powder  without  wholly  destroying  its  pulverulent  condition; 
3rd,  the  proper  packing  of  this  previously  dampened  powder  in  the 
displacement  apparatus,  which  should  be  firmly  done  when  ad- 
missible. 
In  conclusion,  the  great  advantages  of  the  displacement  pro- 
cess, as  thus  conducted,  consist  in  the  facility  it  affords  of  ob- 
taining very  concentrated  solutions  of  vegetable  substances  in  a 
comparatively  short  period  of  time ;  by  which  we  are  enabled  to 
prepare,  at  short  notice,  the  various  officinal  tinctures,  syrups, 
and  extracts  ;  and  in  this  latter  case  it  is  especially  useful  on 
account  of  the  first  portions  of  liquid  which  pass  containing  most 
of  the  activity  of  the  substance  thus  treated,  which  should  be 
reserved  for  separate  evaporation  without  long  exposure  to  heat 
and  consequent  injury. — Jour,  and  Trans.  Md.  Coll.  Pharm. 
March,  1859. 
