Am.  Jour.  Pharm. ) 
April,  1910.  J 
Correspondence. 
191 
solvent,  exerting  a  greater  range  of  solvent  action  on  subsequent 
portions.  It  is  not  necessary  for  percolation  to  be  continuous. 
After  two  or  three  days'  maceration,  percolation  can  proceed  until 
the  percolate  shows  evidence  of  less  saturation  and  then  be  stopped 
for  another  short  period  of  maceration.  We  have  noticed  that  a 
percolation  conducted  at  a  temperature  of  500  compared  with  the 
same  drug  and  menstruum  at  70  0  requires  more  maceration  and 
much  slower  percolation  to  obtain  the  same  degree  of  extraction. 
While  the  fact  is  well  known,  the  principle  is  often  lost  sight  of. 
We  recall  being  shown  over  the  laboratory  of  a  retail  pharmacy 
where  the  percolations  were  being  conducted  near  a  large  window 
in  the  coldest  portion  of  the  room  because  so  much  less  time  was 
required  of  the  workers  at  the  inconveniently  low  temperature  than 
was  required  at  other  processes.  At  the  time  of  our  visit  the 
temperature  was  about  45 0  F.  and  the  operator  was  not  properly 
extracting  his  drugs.  For  general  use  the  instructions  of  the 
Pharmacopoeia,  as  to  method  of  conducting  percolation,  are  suffi- 
ciently explicit. 
Wilbur  L.  Scoville,  Detroit,  comments  as  follows  on  this  sub- 
ject: I  have  never  done  any  direct  work  on  the  comparative  results 
of  preparations  made  by  maceration  with  those  made  by  percolation. 
I  am  aware  that  the  maceration  process  produces  a  tincture  that 
is  less  prone  to  precipitate  but  under  the  best  of  conditions  it  is 
more  wasteful,  and  the  precipitation  in  the  percolation  process  can 
be  reduced  to  a  minimum  by  mixing  all  the  menstruum  necessary 
before  beginning,  and  so  avoiding  slight  changes  in  the  menstruum 
during  the  process.  Furthermore,  except  in  the  cases  of  a  very 
few  oleoresinous,  resinous,  and  astringent  drugs,  the  active  prin- 
ciples of  which  are  easily  accessible  and  quickly  soluble,  macera- 
tion is  the  more  important  part  of  percolation.  Pressure  percolators 
have  been  proved  inadequate  many  times,  and  long  macerations, 
seven  to  ten  days,  are  frequently  an  advantage,  particularly  in 
making  concentrated  preparations. 
While  a  trained  worker,  taking  special  pains  in  a  series  of 
comparative  experiments,  may  show  some  superior  results  for  the 
maceration  process,  I  believe  that  the  average  worker,  on  whom  the 
necessity  for  full  maceration  and  slow  percolation  has  been  im- 
pressed, will  get  more  uniform,  and  on  the  average  better,  results 
by  the  process  of  percolation.  This  is,  however,  a  tribute  to 
maceration  quite  as  much  as  to  percolation. 
