ON  FRACTIONAL  PERCOLATION.  341 
fractional  percolation,  contains  fifteen  grains  less  of  solid  matter, 
the  officinal  preparation  contains  but  one  hundred  grains  of  solid 
matter  in  the  fluidounce  not  heated  ;  whereas  the  former  con- 
tains one  hundred  and  twenty-eight  grains.  Fractional  percola- 
tion appears  therefore  to  be  well  adapted  to  the  preparation  of 
fiuid  extract  of  senna,  unless  we  take  the  ground  that  that  por- 
tion of  senna,  which  is  subjected  to  heating,  is  not  injured 
thereby. 
A  series  of  experiments  with  rhubarb  was  next  undertaken, 
but  unfortunately  I  was  unable  to  complete  them,  and  had  to 
content  myself  with  the  two  following : 
Experiment  5. — Twenty-four  troy  ounces  of  rhubarb,  in  moderately  fine 
powder,  was  treated  with  diluted  alcohol  by  fractional  percolation,  pre- 
cisely like  the  senna  in  Experiments  1  and  3,  with  the  following  results  : 
Amount  of  solid  extract — 
In  24  f.  ounces  of  fluid  extract  3,432  grains. 
In  1  f.  ounce  '*        "  143  grains. 
In  exhaust  percolate  for  24  f.  ounces  of  fluid 
extract  2,058  grains. 
In  exhaust  percolate  fori  f.  ounce  of  fluid  extract  85*75  grains. 
From  1  troy  ounce  of  .'rhubarb  228*75  grains. 
Experiment  6. — Twenty-four  troyounces  of  the  same  lot  of  rhubarb, 
treated  according  to  the  Pharmacopoeia  process,  with  alcohol,  followed 
by  diluted  alcohol  gave  the  following  results : 
Amount  of  solid  extract — 
In  reserve  for  24  f.  ounces  of  fluid  extract       3,618  grains. 
In       "     '*     1  f.  ounce  "       "  150*75  grains. 
In  additional  percolate  for  24  f.  ounces  of  fluid 
extract  2,364  grains. 
In  additional  percolate  for  1  f.  ounce  of  fluid  extract         98*50  grains. 
Inl  fluid  ounce  of  finished  fluid  extract  249*25  grains. 
In  exhaust  percolate  for  24  f.  ounces  of  fluid  ex- 
tract 84  grains. 
In  exhaust  percolate  for  1  f.  ounce  of  fluid  extract  3  50  grains. 
From  one  troyounce  of  rhubarb  252*75  grains. 
The  results  of  the  last  two  experiments  are  exceedingly  un- 
favorable, as  regards  fractional  percolation  upon  rhubarb,  as  the 
reserve  portion  by  the  officinal  process  contained  more  i  olid  ex- 
tract than  the  fluid  extract  made  by  fractional  percolation  con- 
tained altogether.    That  a  troy  ounce  of  rhubarb  yields  more 
