410 
ON  LIQUOR  FERRI  IODLDX. 
h.  Vial  e.  was  excluded  from  the  light  by  being  wrapped  in 
dark  colored  paper,  and  thus  set  in  the  sun-light.  Four  weeks 
exposure  in  this  way  did  not  produce  any  perceptible  change  of 
color. 
*.  The  same  vial  was  wrapped  in  thin  white  unsized  paper,  and 
placed  in  the  same  position.  Gradually,  though  very  slowly,  it 
was  decolorized. 
Part  IV. — Action  of  light  and  air. 
h.  Vials  g.  and  i.  were  uncorked,  fresh  air  blown  in  and  im- 
mediately well  corked,  and  put  back  in  the  sun-light.  At  first, 
the  liquid  was  slightly  colored  on  the  surface ;  the  color  descend- 
ing down  to  about  the  middle  of  the  liquor,  it  gradually  became 
colorless  again ;  the  change  progressing  upwards. 
The  vials,  whose  contents  have  been  decolorized,  do  not  con- 
tain the  slightest  precipitate,  and  the  liquor  is  of  neutral  reaction, 
has  the  taste  of  a  fresh  prepared  article,  but  is  of  a  brighter  appear- 
ance ;  although  experiment  k.  has  been  repeated  four  times  with 
two  of  the  vials.  It  is  evident  that  the  iron,  which  had  been  separat- 
ed by  the  interference  of  oxygen,  was  taken  up  again  in  solution. 
How  this  recombination  takes  place,  in  what  way  the  oxygen  is 
separated  from  the  sesquioxide  of  iron,  I  cannot  tell  at  present; 
other  experiments  which  I  intend  to  make,  may  probably  throw 
some  light  on  this  subject. 
From  the  above  experiments,  I  arrive  at  the  following  conclu- 
sions : 
1.  That  no  decomposition  of  the  solution  of  iodide  of  iron, 
(U.  S.  P.)  takes  place  by  the  action  of  light,  (Part  I.) 
2.  That  this  decomposition  and  oxidation  is  attributable  only 
to  the  presence  of  oxygen ;  but 
3.  That  the  oxidation  takes  place  in  a  much  shorter  time,  the 
more  the  liquid  is  exposed  to  the  action  of  light,  (Part  II.) 
4.  That  on  the  contrary,  the  direct  sun-light  possesses  the 
power  of  restoring  the  original  color  and  composition  in  air-tight 
vessels,  bleaching  it  almost  to  the  disappearance  of  all  color, 
(Part  III.) 
5.  That  the  heat  of  the  sun  alone  can  not  perform  this  change, 
(experiment  A.)  although  it  may  promote  it. 
6.  That  the  sun-light  changes  it  the  faster,  the  freer  it  is  al- 
lowed to  act  on  it,  (experiment  f.  g.  and  L 
