Am.  Jour.  Pharm.  ) 
December,  1920.  ) 
The  Theory  of  Percolation. 
867 
and  has  been  approved  by  many  students  of  extraction.  It  is 
based  upon  the  idea  of  combining  maceration  with  percolation  in 
such  a  way  that  every  portion  of  fresh  mentruum  added  to  a  drug 
in  a  percolator  shall  have  as  much  or  more  opportunity  to  macer- 
ate the  drug  as  the  first  portion  of  menstruum  has  under  the  official 
procedure.  As  is  well  known,  the  early  portions  of  percolate  con- 
tain the  most  readily  soluble  constituents  of  the  drug  so  that  the 
later  fractions  of  the  menstruum  encounter  the  most  difficult  por- 
tions of  the  extractive  to  dissolve.  The  common  idea  seems  to 
be  that  the  rate  of  flow  of  percolate  may  be  accelerated  as  the  per- 
colation proceeds  inasmuch  as  the  quantity  of  extractive  is  diminish- 
ing and  therefore  does  not  require  as  long  for  solution,  whereas  the 
converse  is  really  the  true  condition. 
The  principle  of  interrupted  percolation  is  as  follows:  The  drug 
is  moistened  and  packed  in  the  usual  way  and  is  then  macerated 
for  the  official  period  with  enough  menstruum  to  "flood  it;"  at  the 
termination  of  the  period  of  maceration  percolation  is  begun  and  a 
quantity  of  percolate  equivalent  to  the  volume  of  menstruum  first 
added  is  collected.  Meanwhile  fresh  menstruum  has  been  added 
to  take  the  place  of  that  percolated  out  and,  when  the  first  volume 
of  percolate  has  been  obtained,  the  percolation  is  stopped  and  the 
drug  allowed  to  macerate  in  the  second  portion  of  menstruum. 
After  a  certain  time  percolation  is  again  allowed  to  proceed  until 
the  second  menstruum  has  been  percolated  out,  a  third  portion  of 
fresh  menstruum  having  been  added  to  the  drug.  The  percolation 
is  again  stopped,  the  drug  again  macerated,  and  the  procedure 
continued  until  the  drug  is  exhausted. 
vSearby^  strongly  approved  this  method  as  also  did  Edel-  who 
claims  that  the  reserved  portion  in  the  manufacture  of  fluidex- 
tracts  by  this  method  contains  more  extract  than  that  in  the 
U.  vS.  P.  process.  J.  W.  Colcord'^  was  also  of  the  belief  that  alternate 
maceration  and  percolation  is  the  best  procedure  for  the  extraction 
of  a  drug.  vSeifert  shows  that  interrupted  percolation  is  of  especial 
value  with  drugs  which  yield  large  amounts  of  extract,  as  senna  or 
cinchona.  With  resinous  drugs  such  as  ginger,  the  process  did  not 
present  any  advantage  over  simple  percolation.  vSeifert  reports  the 
following  results. 
'  Discussion,  Proc.  Calif.  Ph.  A.  1892,  125. 
-'  West.  Dru^.  1893,  218;  1899,  216. 
Pharrn.  Rec.  6,  i97/i«S6). 
