Am.  Jour.  Pharm. ) 
November,  1920.  ) 
The  Theory  of  Percolation. 
773 
ter,  Savary,  Taylor,  and  others  which  gave  evidence  of  intelHgent  com- 
prehension of  the  principles  involved  in  percolation  and  careful  study 
of  the  drug  and  the  menstrua  suitable  for  its  extraction. 
The  critical  study  of  the  process  of  percolation  began  in  1858  with 
Squibb's  first  paper/  although  one  critical  commentary,  that  of 
Deane,^  had  already  been  published.  For  the  next  twenty-five 
years  Squibb  frequently  contributed  critical  essays  on  percolation 
to  the  periodical  literature.  Procter,  Maisch,  Diehl,^  Redwood,^ 
Signoret,^  Parrish,^  Graham,"^  A.  B.  Taylor ^  Mclntyre,^  Rem- 
ington^^, Moore,^^  Robbins,^^  and  J.  U.  Lloyd  supplemented  and  ex- 
tended the  work  of  Squibb.  Lloyd  appears  first  in  1877^^  and  within 
a  few  years  was  easily  the  leader  in  this  field  of  investigation.  He 
has  devoted  much  of  his  time  during  the  past  forty  years  to  a  study 
of  percolation  and  the  conditions  affecting  the  process  and  its  products. 
We  owe  by  far  the  larger  proportion  of  our  knowledge  of  extraction 
to  his  patient  industry  and  unselfishness. 
Early  in  the  Sixties,  Squibb  interested  himself  in  the  question  of 
economy  of  alcohol  in  percolation^^  following  the  increased  price  of 
that  solvent  due  to  federal  taxation.  This  study  led  to  the  develop- 
ment of  his  famous  "repercolation"  process and  led  to  a  controversy 
that  stimulated  investigation  and  developed  page  after  page  of  most 
valuable  observations  and  deductions.  The  process  of  Squibb  was 
not  made  official  in  the  U.  S.  P.  until  the  ninth  revision  (1916)  although 
permission  to  use  it  was  given  in  earlier  revisions.  It  was  considered 
that  the  complicated  manipulations  of  Squibb's  method  were  not 
suited  for  general  pharmaceutical  use^^  although  it  was  admittedly  an 
improvement. 
1  This  Journal,  Vol.  30,  97,  (1858). 
2  Pharm.  Jour.  Vol.  i,  61,  (1841). 
3  This  Journal,  Vol.  41,  337,  (1869). 
^  Pharm.  Jour.  Vol.  23,  523,  (1864). 
^  This  Journal,  Vol.  33,  319,  (1861);  from  Repertoire  de  Pharm. 
^  This  Journal,  Vol.  31,  327,  (1859). 
^  This  Journal,  Vol.  31,  354,  (1859). 
^  This  Journal,  Vol.  42,  150,  (1870). 
^  This  Journal,  Vol.  45,  210,  (1873). 
»o  This  Journal,  Vol.  46,  7,  (1874). 
^1  This  Journal,  Vol.  46,  497,  551,  (1874). 
12  This  Journal,  Vol.  50,  329,  (1878). 
Proc.  A.  Ph.  A.  1877,  408. 
14  Proc.  A.  Ph.  A.  1865,  201 ;  This  Journal,  Vol.  38,  109,  (1866). 
1^  Proc.  A.  Ph.  A.  1867,  391. 
'6  This  Journal,  Vol.  41,  295,  (1869).  - 
