Fluid  Extracts  by  Refer  eolation. 
\  Am.  Joar.  Pharro. 
j       May,  i278. 
the  column  is  several  inches  short  of  the  height  of  the  liquid  in  the 
percolator.  But  as  exhaustion  progresses,  and  the  liquid  in  this  column 
becomes  less  dense  its  counterbalancing  height  becomes  greater,  until 
finally  when  the  powder  is  exhausted  and  the  liquid  within  and  without 
are  of  the  same  density  the  column  rises  to  the  level  of  the  liquid  within 
the  percolator  minus  the  friction  and  capillarity.  When  the  percola- 
tion is  to  be  started,  the  syphon  is  simply  pushed  down  through  the 
Scale,  one-sixth  of  the  actual  linear  size. 
rubber  until  the  liquid  flows  over,  and  then  the  rate  is  established  by 
carefully  raising  or  lowering  the  syphon.  This  sliding  joint  for  vary- 
ing the  length  of  this  column  of  liquid  at  will,  being  understood,  the 
other  details  are  plain  enough,  whilst  the  charging  and  the  general 
management  are  the  same  as  in  the  smaller  and  larger  percolators. 
However  attractive  the  simplicity  of  the  lamp  chimney  arrangement 
may  appear  it  does  not  yield  so  good  results  as  the  form  of  percolator 
reproduced  here,  with  slight  improvements,  from  the  "  Proceedings  of 
the  Amer.  Pharm.  Asso."  for  1872,  p.  182,  for  several  reasons.  First 
because  the  principles  involved  are  not  so  well  carried  out,  and  secondly 
