118   PROPOSED  ECONOMY  OF  ALCOHOL  IN  PERCOLATION,  ETC. 
fluidounces ;  and  if  this  fluid  be  alcoholic,  ten  or  twelve  fluidounces 
of  it  may  be  easily  pushed  out  of  it  by  displacement  with  water 
without  the  smallest  risk  of  admixture  of  the  percolate  with 
the  water.  In  using  the  officinal  quantity  of  seed,  therefore, 
it  is  only  necessary  to  have  the  menstruum  four  to  six  fluid- 
ounces  in  excess  of  the  required  percolate  when  water  is  used. 
One  precaution,  however,  is  necessary  to  the  best  attainable  re- 
sults, namely,  that  the  water  be  poured  on  top  just  as  the  last 
of  the  spirit  disappears  from  the  surface.  Attention  to  this 
point  will  always  save  two  to  three  fluidounces  of  the  menstruum, 
as  a  small  excess  will  then  form  a  partition,  which  follows  the 
percolate  down,  and  effectually  protects  it  from  admixture  with 
the  water.  Should  the  percolation  be  arrested  by  the  impaction 
of  the  surface,  which  sometimes  follows  the  application  of  water, 
as  in  ipecacuanha,  it  is  only  necessary  to  scrape  off  the  impacted 
or  impervious  surface,  and  renew  the  water  from  time  to  time. 
In  the  table  upon  the  opposite  page  are  given  the  results  •  of 
some  of  the  percolations  of  colchicum  seed  made  for  this  paper. 
In  the  first  division,  the  first  column  indicates  the  portion  of  the 
percolate  represented  by  the  figures  upon  the  same  line  in  the 
next  column  ;  these  two  columns  recording  an  experiment  wherein 
every  fluidounce  of  percolate  to  the  twenty-fifth  was  tested  by 
evaporation.  The  table  then  commences  again  with  a  column  indi- 
cating the  portion  of  percolate  represented  by  a  weight  of  solid 
extract  upon  the  same  line  with  it  throughout  the  remainder  of 
the  table.  The  "  Total "  is  the  sum  obtained  by  the  addition  of 
.  all  the  portions  of  dry  extract.  The  "  Reserved  Percolate  "  is  a 
repetition  of  the  line  above,  marked  "  1st  12  fg."  The  "  Final 
Percolate  "  is  the  whole  extract  yielded  after  the  reserved  per- 
colate;  and  the  "Finished  Fluid  Extract"  is  the  yield  of  the 
finished  extract  after  filtration.  It  should  therefore  always  fall 
short  of  the  sum  of  the  weights  of  extract  by  addition,  but  in 
two  instances  does  not  do  so.  The  percolation  was  in  several 
instances  carried  beyond  the  point  indicated  in  the  Pharmaco- 
poeia, to  exhibit  the  rate  of  exhaustion.  This  extract  consists 
largely  of  oil,  and,  from  some  crude  trials,  is  probably  quite 
inert.  The  average  may  therefore,  probably,  be  safely  taken 
as  the  weight  of  the  constant  quantity  of  inert  matter ;  and  if 
