ON  LIQUOR  FERRI  IODIDI. 
409 
keeping  admirably  well  for  a  considerable  period,  especially  when 
protected  from  the  air  and  light  and  in  a  cool  situation. 
These  contradictory  remarks  have  induced  me  to  make  some 
experiments  on  the  subject,  the  results  of  which  I  will  give  in 
this  paper. 
The  liquor  ferri  iodidi  which  I  used  was  prepared  according  to 
the  formula  of  the  U.  S.  Pharmacopoeia,  omitting,  however,  the 
application  of  heat,  the  union  of  the  iron  and  iodine  being  effected 
in  a  flask  by  constant  rotation.  The  liquor  was  free  of  iodine, 
not  a  trace  of  it  was  shown  by  starch.  The  experiments  I  divide 
into  four  parts. 
Part  I. — The  vials  filled  and  well  corked  to  exclude  the  air 
from  the  liquid, 
a.  A  vial  was  placed  in  the  diffused  daylight,  care  being  taken 
to  seclude  it  from  the  direct  and  even  reflected  sunlight.  It  was 
unchanged  after  the  lapse  of  three  weeks. 
b.  A  vial  was  exposed  to  the  direct  sun  rays.  The  liquid, 
although  at  first  of  the  required  pale  greenish  color,  soon  became 
lighter,  and  after  a  week  was  of  a  beautiful  clearness  and  light- 
ness, bleached  until  it  was  nearly  colorless. 
Part  II — The  air  freely  admitted  to  the  liquid,  the  vials  being 
half  full  and  covered  with  gauze. 
c.  A  vial  was  exposed  to  the  sun.  The  liquid  soon  assumed  a 
reddish  tinge,  and  after  two  weeks,  had  altogether  the  appear- 
ance of  a  solution  of  iodine. 
d.  A  vial  was  placed  in  common  day-light.  The  solution, 
though  more  slowly,  underwent  the  same  change. 
e.  A  vial  was  put  in  a  dark  place,  carefully  protected  from  the 
light.  A  week  afterwards  it  had  assumed  a  light  reddish  brown 
color,  not  so  deep,  however,  as  d.  after  the  same  period. 
Part.  III. — Action  of  light  on  the  colored  liquor  ferri  iodidi  in 
carefully  corked  vials. 
/.  The  vial  from  experiment  c.  was  filled  up  with  the  original 
liquid,  and  exposed  to  the  sun-light. 
g.  Vial  d.  without  being  filled  up,  was  placed  as  before.  The 
solution  in  both  vials  soon  became  lighter,  and  at  last  of  the  same 
brightness  as  vial  b. 
