190  Correspondence.  ]Am\p?Sr'i9ioarm" 
Prof.  E.  A.  Ruddiman,  Nashville,  Tenn.,  writes  as  follows : 
My  experience  on  "  The  Relative  Value  of  Percolation  and  Macera- 
tion "  has  been  limited,  so  far  as  comparing  these  two  processes 
on  individual  drugs  is  concerned.  I  have  found  the  pharmacopceial 
directions,  as  when  to  percolate  and  when  to  macerate,  generally 
satisfactory.  I  cannot  agree  with  Professor  Oldberg  in  the  state- 
ment made  at  the  Los  Angeles  meeting  of  the  American  Phar- 
maceutical Association  "  that  any  plant  tincture  of  10  per  cent, 
strength  can  be  far  more  conveniently  prepared  by  maceration 
than  by  percolation,  and  just  as  effectively."  That  has  not  been 
my  experience  either  in  the  manufacturing  laboratory  or  in  the 
college  laboratory. 
Two  preparations  made  by  percolation  that  have  given  me 
trouble  are  fluidextract  of  squill  and  tincture  of  opium.  In  the 
case  of  the  former  I  have  had  frequently  to  resort  to  maceration 
and  straining,  and  clearing  by  standing.  In  the  case  of  laudanum 
I  am  fully  convinced  from  experiments  which  I  have  made  in 
preparing  this  tincture  and  assaying  the  product,  and  in  assaying 
the  tinctures  made  by  a  large  number  of  druggists,  that  the  official 
process  does  not  exhaust  the  drug.  The  opium  should  be  exhausted 
as  directed  under  the  tincture  of  deodorized  opium  and  the  per- 
colate evaporated  if  necessary. 
In  some  cases  I  have  found  it  desirable  to  use  a  coarser 
powder  for  percolation  than  directed  by  the  Pharmacopoeia. 
E.  L.  Patch,  Stoneham.  Mass.,  says :  While  maceration  may  be 
advisable  for  gum-resinous  drugs,  or  drugs  largely  soluble,  as 
guaiac,  myrrh,  aloes,  etc.,  for  the  larger  number  of  ordinary  drugs 
percolation  is  to  be  preferred. 
If  maceration  is  resorted  to  in  such  cases  (ordinary  drugs) 
and  stirring  of  the  drug  and  menstruum  is  followed,  quite  a  portion 
of  soluble  matter  is  retained  by  the  drug  and  can  only  be  removed 
by  strong  pressure,  which  is  usually  inconvenient  and  annoying. 
If,  on  the  other  hand,  the  vessel  has  an  outlet  permitting  the 
saturated  or  supersaturated  liquid  to  flow  off  at  intervals,  as  in 
percolation,  more  thorough  extraction  should  result.  We  should 
remember  that  percolation  is  a  process  of  solution  and  subject  to 
the  same  rules  as  ordinary  solution,  and  is  affected  by  extent  of 
surface  exposed  to  action  of  solvent,  to  character  of  solvent,  tem- 
perature, etc.  The  solvent  may  extract  certain  principles  from  the 
upper  layers  of  drug  in  a  percolator  and  become  a  compound 
