242  Fluid  Extracts  by  Rep er eolation.     \ An ^™-J7trm' 
course  the  principles  involved  when  once  understood  can  be  applied  to 
vessels  of  any  kind  and  size  by  means  of  common  glass  tubing,  and  in 
order  to  have  these  principles  tried  by  less  prejudiced  persons  than  the 
writer  the  mechanism  will  now  be  given  as  plainly  as  possible,  as  appli- 
cable to  this  best  form  of  apparatus. 
The  percolator,  a,  is  of  the  form  of  the  more  modern  glass  or  tin 
percolators  somewhat  funnel  shaped  to  allow  substances  to  swell  with- 
out becoming  impacted,  but  having  no  special  angle.  The  smaller  has 
a  glass  stem  and  foot  like  an  ordinary  celery  glass,  and  the  larger  is  an 
ordinary  stone  ware  pot  neither  having  an  opening  in  bottom  nor  sides. 
The  smaller  is  about  16  inches  =  40  centimetres  in  height,  of  which 
height  about  4  inches  =  10  centimetres  is  stem  and  foot,  and  is  of  a 
proper  capacity  for  16  to  20  ounces  =  500  to  600  gram,  of  material 
and  a  proper  stratum  of  menstruum.  The  bottom,  internally  should 
be  about  2  inches  —  5  centimetres  in  diameter  and  should  be  flat, — 
not  cup-shaped  as  the  glass-blowers  are  apt  to  leave  it.  A  rim  of  glass 
is  made  upon  the  upper  edge  or  lip,  to  strengthen  it,  and  this  lip  is 
ground  off  so  that  the  cover  may  fit  accurately  to  prevent  loss  by  evap- 
oration. The  height  of  the  foot  and  stem  is  not  a  matter  of  indiffer- 
ence, since  if  too  short  it  has  to  be  set  upon  a  stand  in  order  that  the 
receiving  bottle  may  be  conveniently  changed. 
The  larger  percolator,  is  a  stone  ware  pot  of  about  2  gallons  = 
7557  cc-  capacity, — 10  inches  =  24  centimetres  high  and  across  the 
top,  by  about  6  inches  =  14*4  centimetres  across  the  bottom,  inside, 
and  it  will  conveniently  hold  4*5  to  6*5  pounds  ==  2  to  3  kilos,  and  a 
proper  stratum  of  menstruum.  Both  cuts  are  made  one-sixth  the 
actual  linear  size,  and  the  same  letters  refer  to  the  same  parts  of  each, 
so  that  one  description  applies  to  both. 
A  disk  of  blanket,  b,  is  cut  of  such  a  size  and  shape  as  to  lie  flat 
upon  the  bottom,  and  cover  it  entirely.  Another  disk  of  the  same 
material,  but  a  little  larger,  c,  is  made  with  a  crucial  incision  in  the 
centre,  so  that  it  may  be  stretched  over  the  end  of  the  well-tube,  e. 
The  central  or  well  tube,  is  a  simple  piece  of  glass  tube  about  12 
inches  =  30  centimetres  long,  by  '5  to  '75  inch  =  1*5  to  2  centime- 
tres internal  diameter,  irregularly  notched,  or  knawed  off  obliquely  at 
the  lower  end.  One  end  of  this  well  tube,  ^,  is  pushed  through  the 
crucial  cut  in  the  centre  of  the  upper  disk  of  blanket,  and  the  blan- 
ket is  pushed  to  the  other  end  of  the  tube  so  that  the  corners  made  by 
I 
