THE  PROCESS  OF  PERCOLATION  OR  DISPLACEMENT  35^ 
The  great  beauty  and  excellency  of  the  process  I  consider  to 
be  in  the  concentrative  power,  rapidity  and  efficiency  of  its 
operation.  It  is  frequently  very  desirable  to  obtain  quickly 
solutions  at  once  so  concentrated  as  to  possess  nearly  or  quite 
all  that  is  active  in  the  substance  under  treatment,  and  which 
in  quantity  is  sometimes  less,  and  often  not  more  than  would 
be  sufficient  to  thoroughly  moisten  the  substance  in  accordance 
with  the  officinal  directions ;  and  being  thus  diffused  through 
the  mass  it  cannot  be  so  completely  displaced,  and  at  the  same 
time  the  material  so  thoroughly  exhausted,  as  it  could  be  if  the 
process  was  conducted  under  other  circumstances. 
What  then  are  the  circumstances  so  favorable  to  the  success- 
ful prosecution  of  the  process,  in  the  attainment  of  results  so 
reliable  and  advantageous  ?  It  may  not  be  out  of  place,  in  the 
first  instance,  briefly  to  allude  to  the  apparatus.  This  may  be 
of  various  materials,  as  metal,  glass,  porcelain,  &c,  and  either 
cylindrical  or  slightly  conical,  terminating  somewhat  funnel- 
shaped,  and  with  or  without  a  diaphragm,  as  this  can  be  sup- 
plied with  a  substitute  of  carded  cotton. 
For  almost  all  the  operations  of  the  pharmaceutist,  except  in 
a  few  instances,  when  a  larger  apparatus  is  required,  I  know  of 
no  instrument  that  answers  the  purpose  better  than  the  common 
glass  funnel ;  funnels  less  cone-shaped  than  would  be  selected 
for  filtering  purposes,  ordinarily  termed  badly-shaped  funnels, 
and  which  can  be  had  at  a  very  trifling  expense.  These  may 
be  arranged  for  an  apparatus  by  having  the  upper  part  of  the 
neck  filled  with  carded  cotton  on  which  the  material  rests  ;  over 
this  a  piece  of  perforated  paper  is  placed,  and  in  some  cases 
there  will  be  an  advantage  in  placing  on  the  paper  a  piece  of 
perforated  tin,  having  a  small  knob  in  the  centre,  by  which  to 
handle  it.  I  recommend  the  funnel,  because,  in  the  first  place, 
it  is  always  at  hand,  and,  if  not,  can  be  supplied  at  so  little  cost; 
and  secondly,  because  I  know  that  its  form  does  not  impede  the 
process,  although  some  have  so  asserted ;  and  lastly,  because, 
being  glass,  it  enables  the  operator  to  watch  the  process,  and  see 
whether  or  not  it  is  progressing  satisfactorily.  On  this  latter 
account  I  prefer  glass  instruments  before  all  others.  In  very 
large  operations  the  form  of  the  apparatus  may  be  adapted  to 
the  occasion,  as  the  experience  of  the  operator  may  suggest. 
