'^"Aigri?;^™'}  Convenient  Apparatus  for  Hot  Filtration.  355 
for  the  purposes  of  the  manufacturer,  it  is  not  suited  to  the  wants  of 
the  analytical  chemist.  The  first  form  occupies  much  space,  and  both 
forms  must  be  had  in  great  variety  of  sizes  to  fit  funnels  of  various 
dimensions.  A  small  funnel  is  nearly  lost  to  view  in  a  large  jacket, 
and  a  large  funnel  is  not  heated  by  a  small  one.  Then  again,  only 
well-made  funnels,  whose  sides  are  inclined  at  an  angle  of  60°,  will  fit 
the  conical  opening.  Moreover,  the  fact  that  the  apparatus  is  con- 
structed of  metal  is  in  itself  a  disadvantage.  Only  extraordinary  care 
will  keep  the  metal  clean  and  bright  in  the  atmosphere  of  a  laboratory. 
The  disadvantage  could  be  largely  overcome  by  nickel-plating  the 
metallic  box,  but  we  have  not  seen  this  luxury  introduced.  In  the 
filtration  of  liquids,  giving  rise  to  very  acid  fumes,  the  use  of  a  metallic 
jacket  is  hardly  admissible. 
The  second  apparatus  alluded  to  is  that  contrived  by  Dr.  A.  Hor- 
vath,  and  described  in  the  "Annalen  der  Chemie  und  Pharmacie,"  vol. 
clxxi,  page  135,  1874.*  A  tube  of  soft  lead,  one  centimetre  thick,  is 
wound  around  a  funnel  in  the  form  of  a  spiral,  one  end  being  con- 
nected by  a  tightly-fitting  cork  with  a  flask  placed  at  a  convenient  dis- 
tance, and  the  other  end  of  the  leaden  pipe  communicating  with  a 
recipient  for  the  escaping  vapors.  Steam  being  generated  in  the  flask, 
it  passes  through  the  leaden  tube  and  warms  the  funnel  and  contents. 
This  contrivance  may  work  well,  but  is  not  very  convenient ;  the 
inventor  strangely  enough  adds  that  by  employing  ether,  alcohol,  car- 
bon disulphide,  benzol  or  anilin,  in  place  of  water,  filtration  can  be 
carried  on  at  any  desired  temperature.  The  question  naturally  arises 
why  select  liquids  having  such  low  boiling-points  as  ether  (35*7°  C.) 
and  carbon  disulphide  (46*6°  C.)  to  effect  hot  filtration  ;  surely  the 
cases  are  rare  where  the  temperature  could  not  be  moderated,  if  desired, 
by  generating  steam  less  rapidly.  Then,  too,  it  strikes  us  that  the 
atmosphere  of  a  laboratory,  where  a  dozen  or  more  solutions  are  warm- 
ing by  the  uncondensed  vapors  of  carbon  disulphide,  would  be  any- 
thing but  agreeable  in  its  effect  on  the  olfactors  of  the  occupant !  This 
suggestion  of  the  respected  author  is  apparently  a  case  of  pen-and-ink 
chemistry,  rather  than  the  result  of  practical  experience. 
There  seems  to  be  room,  then,  for  a  simple,  cleanly,  portable  and 
inexpensive  apparatus  for  keeping  the  contents  of  a  funnel  hot  while 
filtering,  and  it  is  believed  that  these  requirements  are  filled  by  the  new 
apparatus  described  in  this  paper. 
American  Journal  of  Pharmacy,"  1874,  p.  275. 
