ORGANIC  MATTER  OF  THE  AIR. 
447 
before.  During  the  period  of  filling  the  vessel  the  surface  of  the 
liquid  is  reduced  to  its  smallest  amount,  and  the  change  it  under- 
goes is  either  inappreciable,  or  so  constant  as  not  to  affect  the 
results. 
In  analysing  the  air  in  this  manner,  it  is  found  that  a  decided 
result  is  attained  in  about  five  minutes.  Sometimes  the  result 
is  decided  in  one ;  that  is,  there  is  a  termination  to  the  rapid  ac- 
tion. This  peculiarity  is  probably  to  be  explained  by  the  follow- 
ing experiments.  If  we  pour  decomposing  matter  on  the  per- 
manganate solution,  it  is  rapidly  destroyed.  If  the  matter  be 
not  in  a  state  of  decomposition,  the  action  is  much  slower. 
These  different  results  promise  a  mode  of  dividing  the  organic 
matter  of  the  air  into  classes  according  to  its  quality.  These 
facts  are  mentioned  merely  as  germs  of  a  future  inquiry.  In 
large  towns,  where  coals  containing  much  sulphur  are  burnt,  the 
sulphurous  acid  takes  the  oxygen  of  the  chameleon,  and  an  ap- 
parently large  amount  of  organic  matter  results.  This  sulphur- 
ous acid  is  of  itself  an  impurity,  perhaps  as  hurtful  as  some  kinds 
of  organic  matter. 
We  measure  by  this  means  the  amount  of  oxygen  needful  for 
the  oxidizable  matter  of  the  atmosphere,  and  all  such  matter  is 
impurity,  in  some  places  entirely  organic ;  in  others,  such  as 
towns,  mixed  with  inorganic  gases. 
Some  of  the  principal  results  obtained  by  this  method  were  as 
follows : — 
Relative  quantities  of  Organic  and  other  Oxidizable  Matter  in  the 
Air  of* 
Manchester  (average  of  131  experiments)  .  .  .  52-9 
"  All  Saints,  E.  wind  (37  experiments)  .  .  524 
"  "       W.  wind,  less  smoky  (33  expts.)  49-1 
«  «       E.  wind,  above  70°  F.  (16  expts.)  584 
«  «  «      below  70°  F.  (21  expts.)  48-0 
"         In  a  house  kept  rather  close       .       .       .  60-7 
In  ajpigstye  uncovered  .......  109-7 
*  A  few  of  these  result3  were  published  in  the  '  Athenaeum '  during  last  sum- 
mer. The  present  numbers  are  somewhat  higher,  being  reduced,  for  the  sake 
of  uniformity,  to  correspond  to  a  vessel  of  100  cubic  inches. 
