ON  CHARCOAL  AS  A  DISINFECTANT. 
167 
peratorine  can  only  be  prepared  from  old  roots  of  Imperatoria  ; 
and  this  the  author  has  found  to  be  perfectly  correct.  In  operat- 
ing upon  strong-smelling  fresh  roots,  the  author  never  obtained 
anything  but  a  sticky  mass,  without  any  trace  of  crystallization, 
and  it  was  only  by  employing  old  roots  that  he  procured  crystal- 
lized imperatorine.  This  circumstance  seems  to  indicate  that 
that  ethereal  and  fatty  oils  contained  in  such  abundance  in  the 
fresh  roots  assist  in  the  formation  of  the  crystallized  impera- 
torine.   The  analysis  of  imperatorine  gave, — 
Carbon  70-06  70-21  24  70-50 
Hydrogen       6-19  6-48         12  5-89 
Oxygen         —  —  6  23-52 
Peucedanine  is  resolved,  by  treatment  with  alcoholic  solution 
of  potash,  into  angelicic  acid  and  oreoseline. — Chem.  Gaz.  Nov. 
1,  1854.,  from  Jour,  fur  Praht.  Chem.  lxii.  p.  275., 
ON  CHARCOAL  AS  A  DISINFECTANT. 
Being  a  Letter  to  the  Editor  of  the  "  Times"  as  published  in  that  Journal  on 
the  22d  November,  1854. 
By  Dr.  John  Stenhouse,  F.  R.  S. 
Lecturer  on  Chemistry  at  St.  Bartholomew's  Hospital,  London. 
The  great  efficacy  of  wood  and  animal  charcoal  in  absorbing 
effluvia  and  the  greater  number  of  gases  and  vapors,  has  long 
been  known. 
Charcoal  powder  has  also,  during  many  centuries,  been  advan- 
tageously employed  as  a  filter  for  putrid  water,  the  object  in  view 
being  to  deprive  the  water  of  numerous  organic  impurities  dif- 
fused through  it,  which  exert  injurious  effects  on  the  animal 
economy. 
It  is  certainly  somewhat  remarkable,  that  the  very  obvious  ap- 
plication of  a  perfectly  similar  operation  to  the  still  rarer  fluid 
in  which  we  live — namely,  the  air,  which  not  frequently  contains 
even  more  noxious  organic  impurities  floating  in  it  than  those 
present  in  water,  should  have,  up  till  February  last,  been  so 
unaccountably  overlooked. 
Charcoal  not  only  absorbs  effluvia  and  gaseous  bodies,  but, 
especially  when  in  contact  with  atmospheric  air,  rapidly  oxidizes 
