248 
Fluid  Extracts  by  Rep er eolation. 
Am.  Jour.  Pharm. 
May,  1S78. 
Then  by  gentle  slow  suction  with  the  mouth  at  the  upper  end  of  the 
glass  tube  the  syphon  is  slowly  rilled,  and  when  filled  the  glass  tube 
and  rubber  are  removed.  As  soon  as  the  dropping  commences  the 
syphon  must  be  raised  or  lowered  until  the  desired  rate  of  dropping  is 
attained.  If  the  syphon  has  to  be  raised  in  order  to  attain  the  rate,  it 
must  be  done  little  by  little  in  order  to  avoid  raising  the  inner  end  out 
of  the  liquid  in  the  well.  The  rate  of  dropping  can  only  be  estab- 
lished with  entire  uniformity  when  the  inverted  automatic  feeding 
bottle  is  used  for  supplying  menstruum,  because  when  the  menstruum 
is  poured  on  from  time  to  time  the  dropping  will  be  a  little  faster  as 
the  outside  level  is  raised  by  each  addition. 
When  weak  percolates  of  diminishing  strength  are  successively  used 
on  top,  the  stratum  of  liquid  should  be  kept  thin,  so  that  each  stronger 
weak  percolate  may  have  nearly  all  sunk  into  the  substance  before  the 
next  weaker  one  is  used.  In  receiving  the  percolate  the  blocks,  «, 
are  used  to  support  the  receiving  bottle  in  any  position,  and  when  the 
percolation  is  to  be  stopped,  or  made  to  go  very  slowly,  during  the 
night  for  example,  this  may  be  effected  either  by  raising  the  syphon 
higher,  or  by  blocking  up  the  receiving  bottle  so  that  the  outer  end  of 
the  syphon  is  immersed  in  the  percolate  received  to  the  necessary 
depth.  Of  course  when  the  receiving  bottle  is  blocked  up  so  that  the 
mouth,  or  any  desired  mark  upon  the  bottle  is  near  the  level  of  the 
liquid  in  the  percolator,  the  bottle  can  never  run  over  nor  the  mark  so 
raised  be  surpassed.  The  dropping  end  of  the  syphon  should  always 
be  inside  of  the  receiving  bottle,  because  thus  all  loss  by  evaporation 
is  avoided,  the  air  inside  the  bottle  being  still,  and  being  saturated.  If 
the  same  rate  of  slow  dropping  was  carried  on  outside  in  the  moving 
air  of  a  room,  and  the  drops  fell  into  a  funnel,  for  example,  about  one- 
fourth  of  the  menstruum  would  be  lost  by  evaporation, — the  more 
volatile  portions  in  greater  proportion,  and  the  percolate  would  be 
turbid  and  unfit  for  use. 
The  last  weak  portions  of  percolate  may  almost  always  be  pushed 
through  by  the  careful  use  of  water  on  top,  and  in  proportion  as  the 
operator  acquires  skill  in  the  management,  little  menstruum  will  be 
lost.  When  exhaustion  is  practically  complete  the  syphon  is  pushed 
down  to  the  bottom  of  the  well,  and  the  last  weak  percolate  drawn  off 
rapidly. 
Then  if  another  portion  of  the  same  substance  is  to  be  put  into  the 
