352 
Facts  Concerning  Filtration. 
(  Am.  Jour.  Pharm. 
(.      July,  1883. 
straining  rather  than  filtration.  With  ordinary  liquids,  when  there  is 
but  little  insoluble  matter,  absorbent  cotton  not  only  strains,  but  by  fairly 
tight  packing  filters  brightly.  In  cases  where  it  is  desired  to  save  the 
deposit,  and  possibly  to  dry  or  incinerate  it,  asbestos  paper  can  be 
recommended ;  the  liquid  passes  through  it  slowly,  but  it  is  very  strong, 
and  it  is  indestructible  by  heat.  Paper  lint,  as  introduced  from 
America  some  few  years  ago,  answered  well  as  a  filtering  medium, 
being  both  strong  and  absorbent ;  but  I  am  not  certain  whether  its 
manufacture  has  been  continued. 
So  far  we  have  considered  filtration  as  conducted  only  in  funnels  or 
funnel-shaped  arrangements,  as  the  various  forms  in  which  atmos- 
pheric pressure  is  commonly  employed  are  described  in  works  which 
treat  of  such  matters.  They  are  chiefly  those  in  which  a  long  column 
of  liquid  is  carried  above  the  point  of  filtration,  as  in  Mr.  Proctor's 
arrangement ;  where  exhaustion  is  obtained  by  means  of  a  syringe 
underneath;  or  suction  by  means  of  a  bent  tube,  as  described  by  Mr. 
Schacht  at  the  iiKieting  of  the  Conference  at  Birmingham  in  1865. 
Recently  there  has  been  advertised  a  '^Filtre  Rapide,''  in  which  the 
filtering  material  is  placed  on  a  frame  or  support  rising  up  within  the 
cylinder  and  forming  a  space  in  the  centre  into  which  the  filtered  liquid 
flows  laterally  to  a  receiver  below.  It  is  a  compact  and  ingenious 
arrangement,  but  I  have  not  any  experience  from  which  to  speak  of  its 
usefulness. 
To  my  mind  uj^ward  filtration  is  the  direction  in  which  we  should 
work,  and  from  which  we  may  expect  the  best  results. 
Some  years  ago  Mr.  William  R.  Warner,  of  Philadelphia,  invented 
an  oil  filter  on  this  principle,  consisting  of  two  vessels  in  superposition, 
measuring  altogether  about  40  inches  in  height  by  10  inches  in  diam- 
eter, and  which  is  said  to  be  capable  of  filtering  a  barrel  of  oil  per  day. 
This,  of  course  would  depend  on  the  nature  of  the  oil  and  the  tempera- 
ture at  which  it  is  used. 
Recently  I  have  devised  a  form  of  upward  filter  in  one  vessel  only, 
and  have  added  to  it  a  suction  tube.  It  occupies  comparatively  little 
space,  is  simple  in  construction,  efficient  in  action,  and  can  be  made  by 
any  tinman  at  little  cost. 
It  consists  of  a  plain  tin  cylindrical  vessel  (a)  with  a  tap-hole  (b)  1 J 
inch  from  the  bottom ;  it  is  22  inches  high  and  8  inches  diameter.  A 
tin  tray  (c  and  Fig.  2),  7  inches  in  diameter,  with  a  vertical  rim  1 
inch  or  IJ  inch  deep,  has  a  hole  (b^)  in  the  rim;  this  and  the  hole 
