AmMaTi8P78arm  }     Fluid  Extracts  by  Rep er eolation.  2 1 1 
lished  in  the  Proceedings  of  that  year,  p.  81.  In  this  paper  the  method 
by  repercolation  was  first  proposed  and  described  as  overcoming  the 
principal  objections  to  the  previous  methods. 
This  method  of  repercolation  has  now  been  exclusively  used  by  the 
writer  for  nearlv  twelve  years  in  the  production  of  many  thousands  of 
pounds  of  all  the  principal  fluid  extracts,  and  the  object  of  this  paper 
is  to  sum  up  this  experience,  and  publish  the  modifications  of  the  pro- 
cess, as  they  have  been  suggested  and  successfully  applied  during  this 
prolonged  experience,  with  a  view  of  bringing  the  process  more  prom- 
inently into  notice  in  order  to  be  critically  examined  and  tested.  The 
general  results  of  the  application  of  repercolation,  in  the  writer's 
hands,  are,  that  no  other  process  yet  proposed  accomplishes  the  main 
objects  so  well ;  and  therefore  that  unless  some  new  process  can  be 
devised  that  may  attain  the  objects  better  and  more  accurately  than 
this,  it  should  be  the  process  adopted  for  the  Pharmacopoeia. 
In  1867  papers  by  the  writer  upon  this  same  subject,  as  applied  to 
the  Cinchonas,  may  be  found  in  The  Amer.  Journ.  of  Pharm.  for 
July,  August  and  September,  and  in  the  Proceedings  of  The  Amer. 
Pharm.  Asso.  for  1867,  p.  391.  All  the  principles  involved  in  perco- 
lation and  repercolation  were  fully  discussed  and  illustrated  in  those 
several  papers,  but  they  seemed  to  attract  little  attention,  and  they  are 
cited  here  to  avoid  recapitulation,  since  they  cover  nearly  every  point 
which  the  writer  has  now  to  bring  forward.  But  the  papers  also 
contain  many  details  which  accumulating  experience  has  improved  and 
materially  modified. 
About  1870  a  new  form  and  arrangement  of  percolator  was  devised 
by  the  writer,  and  was  put  into  practice  so  successfully  that  two  years 
later  in  the  Proceedings  of  The  Amer.  Pharm.  Asso.  for  1872,  p.  182, 
an  account  of  it,  with  a  cut,  were  given  in  detail.  This  contrivance 
has  now  been  in  use  continuously  for  about  8  years,  upon  every  scale 
from  4  ounces  to  about  400  pounds,  and  by  pretty  thoroughly  carrying 
out  the  principles  involved  in  percolation,  it  has  contributed  very 
largely  to  the  success  and  uniformity  of  the  process  in  the  writer's 
hands.  But  the  apparent  complication  of  this  device,  and  the  details 
of  repercolation,  seem  to  have  operated  against  any  general  under- 
standing of  the  process,  so  that  it  has  probably  been  generally  con- 
demned without  sufficient  trial ;  while  the  physical  laws  which  govern 
the  relations  between  liquids  and  solids  in  the  direction  of  discrimina- 
