862 
The  Theory  of  Percolation. 
(  Am.  Jour.  Pharm. 
I     December,  1920. 
cooling.  If  the  deposit  occurs  soon  after  the  percolation  the  case 
is  sufficiently  undesirable  but  if  the  insoluble  matter  does  not  precip- 
itate for  some  time  or  if  the  deposition  is  spread  over  a  long  period 
of  time  it  makes  an  unsightly  product  which  does  not  redound  to 
the  pharmacist's  credit. 
Percolation  with  hot  water,  as,  for  instance,  in  the  extraction 
of  cascara  and  of  triticum,  is  commendable  and  desirable  for,  with 
cold  w^ater  which  percolates  very  slowly  and  which  contains  noth- 
ing of  a  preservative  nature,  molds  are  quite  likely  to  develop  in  the 
wet  drug  which  renders  the  product  unfit  for  medicinal  use. 
OTHER  METHODS  OI^  PERCOLATION. 
One  of  the  prominent  characteristics  of  pharmacists  as  a  class 
is  their  ingenuity  and  this  is  nowhere  more  apparent  than  in  the 
number  and  extent  of  the  processes  which  they  have  devised  in  the 
last  hundred  years  for  extracting  drugs. '  Since  the  early  apparatus 
of  Count  Real^  which  was  the  first  step  in  the  abolition  of  the  use 
of  the  tincture  press  down  to  the  present  time  new  forms  of  apparatus 
and  novel  methods  for  percolation  have  appeared  in  a  continuous 
stream. 
In  the  case  of  most  of  these  novelties  the  words  of  John  U.  Lloyd 
apply  with  significance,  "simple  percolation  is  as  yet  unexcelled 
and  my  experience  with  complex  forms  of  apparatus  has  invariably 
led  to  their  rejection  and  a  return  to  the  simple  percolator."^ 
It  is  my  purpose  here  to  consider  in  detail  first  the  processes 
which  have  been  applied  most  widely  and  then  to  refer  briefly  to  the 
less  common  methods. 
REPERCOIvATlON. 
When  the  price  of  alcohol  rose  following  the  disturbed  conditions 
incident  to  the  Civil  War  it  profoundly  affected  pharmaceutical 
practise.  Dr.  Squibb  set  himself  to  the  task  of  finding  some  method 
for  economizing  the  use  of  alcohol  in  percolation.  His  first  sug- 
gestion was  that  instead  of  using  a  large  volume  of  alcohol  to  ex- 
tract the  weaker  portion  of  a  partly  exhausted  drug,  the  weak  drug 
should  be  sacrificed  and  the  alcohol  saved,  the  pharmacist  being 
satisfied  with  75  per  cent,  of  fluidextract  from  100  parts  of  drug.'^ 
Later^  a  similar  suggestion  was  made  by  F.  B.  Stuart. 
^  Jour,  de  Pharm.  2,  165,  (1816). 
2  Proc.  A.  Ph.  A.  1887,  582. 
^  Proc.  A.  Ph.  A.  186s,  201. 
4  Proc.  A.  Ph.  A.  1888,  250. 
