December,  ^igl^' }         The  Theory  of  Percolation.  873 
Dursse^  patented  a  percolator  with  a  tightly  fitting  cover  which 
may  be  adjusted  to  control  the  rate  of  flow  of  percolate  and  which 
minimizes  evaporation. 
In  1869  Samuel  Campbell  published  his  process  for  the  prepara- 
tion of  fluidextracts.2  Campbell  believed  maceration  to  be  the 
most  important  part  of  percolation.  He  used  glycerin  in  his 
menstrua  and  macerated  the  drug  for  four  days  after  packing  it  in 
a  glass  funnel  percolator.  After  the  maceration  the  drug  was 
percolated  until  the  proper  volume  of  fluidextract  was  obtained 
when  the  operation  was  stopped  and  the  percolate  treated  as  fin- 
ished fluidextract.  This  did  away  with  prolonged  percolation 
to  obtain  weak  percolates  which  must  be  concentrated  and  dissolved 
in  a  reserved  portion.  But  Campbell's  process  did  not  thoroughly 
extract  the  drug.  King,^  Archibald,^  and  Reynolds^  reported 
against  Campbell's  process;  A.  B.  Taylor^  showed  that  the  idea  of 
long  maceration  is  a  good  one.  Campbell  apparently  abandoned 
the  process  later. 
Calvert^  suggested  an  apparatus  for  percolating  with  very  vola- 
tile solvents  which  consists  of  two  "aspirator"  bottles  one  of  which 
is  set  on  a  shelf  and  used  as  a  reservoir  for  menstruum  while  the 
other  is  inverted  and  serves  as  the  percolator.  The  two  bottles 
are  connected  by  tubing  between  the  lower  apertures.  Menstruum 
flows  from  the  reservoir  into  the  percolator  and  the  percolate  may 
be  collected  out  of  contact  with  the  air. 
Taylor  has  suggested^  using  a  portion  of  the  finished  prepara- 
tion from  a  previous  batch  to  moisten  the  drug  and  to  start  per- 
colation before  adding  the  menstruum.  Dieterich^^  describes  the 
Christ-Dieterich  percolator  the  essential  feature  of  which  is  an 
inverted  bottle  of  menstruum  set  into  the  top  of  the  apparatus 
to  furnish  an  automatic  supply  of  menstruum. 
Arny^^  has  devoted  much  attention  to  the  study  of  loss  of  vola- 
1  This  Journal,  Vol.  41,  384,  (1869). 
2  This  Journal,  Vol.  41,  384,  (1869). 
3  This  Journal,  Vol.  42,  29,  (1870), 
This  Journal,  Vol.  42,  117,  (1870). 
s  This  Journal,  Vol.  41,  525,  (1869). 
6  Proc.  A.  Ph.  A.  1869,  390. 
^  This  Journal,  Vol.  44,  102,  (1872). 
«  This  Journal,  Vol.  55,  269,  (1883). 
^This  Journal,  Vol.  55,  55^.  (iJ^8,0- 
^'^  Pharm.  Cenlr.  29,  168,  (1888). 
Proc.  A.  Ph.  A.  40,  169,  (1892). 
