Am.  Jour.  Pharm.  1 
July,  1876.  / 
Rapid  Filtration, 
291 
and  an  accelerated  filtration.  The  total  length  of  the  tube  is  20 
inches,  width  of  the  upper  part  I J  inches,  its  length  6  inches.  The 
narrow  side  tube  w,  is  I  inch  below  the  rim  of  C«  Internal  diameter 
of  lower  part  j%  inch,  its  length  14  inches.  The  lower  part  must  be 
wide  enough  to  allow  air  bubbles  to  rise  or  overcome  the  capillary 
attraction  exerted  by  the  sides  of  the  tube  upon  the  liquid.  The  tube 
is  closed  by  a  perforated  India  rubber  cork,  receiving  the  neck  of  the 
funnel,  the  opening  of  which  reaches  1  or  2  inches  below  the  little 
side  tube  m.  The  whole  is  held  in  position  by  a  retort-stand,  burette- 
holder  or  the  like. 
2.  The  aspirator  A.  Upper  part  1  inch  in  diameter  and  6  inches 
long,  the  bottom  forming  a  cone,  connecting  it  with  the  lower  part  e, 
which  has  J  inch  internal  diameter,  and  is  1  or  more  inches  long.  To 
this  we  attach  a  rubber  tube/^  5  or  more  feet  long,  and  of  the  same 
internal  diameter  of  J  inch.  The  narrow  side-tube  h  is  1  inch  below 
the  top  of  A-  A  perforated  rubber  cork,  provided  with  a  glass  tube  d, 
is  inserted,  as  seen  in  the  sketch.  This  tube  has  j\  inch  internal 
diameter,  extends  downward  about  3  inches,  upward  1  or  2  inches. 
To  this  upper  end  a  rubber  tube  g  is  attached,  destined  to  supply  the 
water  for  the  aspirator,  from  an  elevated  vessel.  If  the  flow  of  the 
water  is  so  regulated  (by  means  of  a  faucet  or  pinchcock)  that  it 
leaves  tube  d  drop  by  drop,  these  drops  falling  into  the  narrow  tube  ey 
and  its  continuation  f,  perpendicularly  beneath  it,  and,  filling  out  its 
entire  width,  act  the  part  of  the  piston  in  a  pump,  as,  by  their  motion 
downwards,  they  carry  with  them  the  air  enclosed  in  the  tube  between 
the  single  drops.  In,  this  way  the  air  in  A>  as  well  as  in  any  vessel 
connected  with  it  by  the  communication  tube  is  rarefied.  The 
aspirator — equal  lengths  of  time  taken  into  consideration — draws  less 
air  if  the  drops  follow  each  other  slower,  but  then  a  higher  effect  is 
produced  by  a  certain  quantity  of  water,  whilst  if  the  drops  fall 
quicker,  the  apparatus  draws  more  air  in  that  time,  but  the  effect  of 
the  same  quantity  of  water  is  diminished.  Thus,  1  volume  of 
water  draws  from  10  to  25  times  its  volume  of  air. 
3.  The  vacuum  regulator  B.  After  several  experiments,  I  found  a 
mercury  valve  of  the  construction  shown  in  sketch  B5  working  as  well 
as  could  be  wished.  B  has  ij  inch  or  more  internal  diameter  and  is 
about  6  inches  long.  The  narrow  side  tubes  k  and  /  are  opposite  each 
other,  and  1  inch  below  the  rim.    A  good  soft  cork,  free  from  holes, 
