Am.  Jour.  Pharm. 
June,  1921. 
Studies  in  Extraction. 
419 
STUDIES  IN  EXTRACTION. 
By  James  F.  Couch. 
I.  THE  RATE  OF  EXTRACTION  OF  PHYTOLACCA  DECANDRA. 
In  a  general  survey  of  the  theory  of  percolation  1  I  have  pointed 
out  the  desirability  of  more  data  on  the  rates  of  extraction  of  vari- 
ous drugs  to  fill  in  certain  gaps  in  our  knowledge  of  percolation. 
The  rate  of  extraction  may  be  determined  in  several  ways :  In  this 
paper  and  in  two  which  are  in  course  of  preparation,  three  methods 
have  been  employed  which  differ  only  in  extensiveness.  Data  al- 
ready published  on  the  rates,  of  extraction  may  be  found  in  the  pub- 
lished works  of  Lloyd,  Squibb,  Mclntyre  and  Robbins,  reference  to 
which  may  be  found  in  above  quoted  survey. 
The  previous  work  on  this  subject,  however,  was  carried  out  at 
the  time  when  the  standard  for  fluidextracts  was  a  grain  per  minim 
instead  of  a  gram  per  millilitre  as  at  present,  and  the  modern  fluid- 
extract  is  but  95.14  per  cent,  of  the  strength  of  that  of  forty  years 
ago.  As  the  earlier  work  was  conducted  with  reference  to  the  for- 
mer standard  it  is  highly  desirable  that  it  should  be  reviewed  with 
respect  to  the  present  standard  for  the  sake  of  exactness  and  com- 
pleteness. In  addition,  the  earlier  work  was  conducted  particularly 
so  solve  questions  of  economy  of  menstruum,  of  time,  or  in  attempts 
to  avoid  evaporation  of  weak  percolates. 
The  following  account  presents  the  results  of  an  inquiry  into  the 
factors  which  govern  the  rate  of  extraction  of  Phytolacca,  the  gen- 
eralizations which  underlie  it,  and  the  conditions  which  obtain.  The 
theory  of  the  process  has  already  been  discussed.2 
It  was  found  that  the  extraction  of  phytolacca  proceeds  in  a 
regular  manner,  but  with  diminishing  velocity,  so  that  the  last  por- 
tions of  extractive  require  a  considerable  volume  of  menstruum  for 
their  removal.  This  is  in  conformity  with  the  published  results  of 
all  previous  investigators  which  bear  at  all  on  the  subject.  There 
appears  to  be  a  point  where  the  cellulose  of  the  drug  exerts  an  at- 
traction for  the  extractive  equal  to  that  of  the  mestruum  for  the 
extractive.    At  this  point  equilibrium  will  be  established  and  the 
1This  Journal,  Vol.  92,  Nos.  11  and  12  (1920). 
2  This  Journal,  Vol.  92,  p.  788,  seq.  (1920). 
