Am.  Jour.  Pharm.  ) 
December,  1920.  ) 
The  Theory  of  Percolation. 
865 
tions  of  sixteen  troy  ounces  each  of  drug  were  extracted  in  succession ; 
the  percolate  was  collected  in  fractions  of  a  pint  each  and  weighed. 
As  pint  No.  I  from  percolation  No.  i  becomes  approximately  pint 
No.  2  from  percolation  No.  2  and  pint  No.  3  from  percolation  No.  3, 
etc.,  the  difference  in  weight  between  the  pints  shows  the  increased 
saturation  due  to  Squibb' s  method. 
This  ingenious  process  has  been  subjected  to  detailed  study  by 
man}^  investigators  and  has  provoked  much  discussion  and  criti- 
cism. Procter^  protested  that  the  complicated  manipulation  in- 
volved in  the  process  made  it  unsuitable  for  the  pharmacopoeia. 
Diehl,-  who  termed  it  "fractional"  percolation,  made  an  extensive 
study  of  it  with  the  cooperation  of  several  other  pharmacists.  He 
concluded  that  fractional  percolation  offers  no  advantages  over  the 
simpler  process.  The  following  figures  taken  from  one  of  Diehl's  ' 
tables  shows  the  percentage  of  the  total  extract  which  was  contained 
in  the  reserved  portion  in  the  two  processes  of  simple  and  frac- 
tional percolation:  • 
Drug.  Simple.  Fractional. 
Taraxacum,  66 . 43  per  cent.  75 . 00  per  cent. 
Lloyd'^  decided  in  favor  of  simple  percolation  after  extensive 
experimentation;  Moore's  results  show  only  a  slight  advantage 
in  repercolation;^  Arny  and  Oxley^  found  simple  percolation  better 
for  gentian;  Kehey*^  did  not  find  repercolation  satisfactory  for 
gentian,  uva  ursi,  or  squill;  and  Sayre  reported  it  insufficient.'' 
J.  W.  Colcord,  after  wide  experience  with  various  forms  of  per- 
colators, concluded  that  repercolation  must  ultimately  become  the 
official  process.^    Andrew^^  found  a  slightly  modified  repercolation 
'  This  Journal,  Vol.  41,  295,  (1869). 
-  Proc.  A.  Ph. A.  1879,  727;   1880,  424;  1878,  681;  This  Journal,  Vol.  41, 
337,  (iH6g);  Pharm.  Rnnd.  7,  2,5,  60,  (1889). 
■This  Journal,  Vol.   50,    12,  (1878). 
'  This  Journal,  Vol.  62,  333,  (1890). 
■'  l^roc.  A.  Ph.  A.  1910,  1 104. 
Prar.  Kansas  Ph.  A.  1897,  15;  Proc.  A.  Ph.  A.  46,  683,  (1898). 
'  -Drii'^.  Circ.  1897,  212;  Proc.  A.  Ph.  A.  1898,  685. 
^  Proc.  Mass.  Ph.  A.  5,  x-jo,  fi886);  Proc.  A.  Ph.  A.  1887,  10. 
Pharm.  Joiir.  68,  336,  ("1902). 
Senna  leaves 
Eucalyptus  leaves 
83.75 
67  •  95 
66.80 
62  .50 
82  .51 
72  . 79 
75  32 
