ON  THE  DETERMINATION  OF  IODINE. 
257 
which  case  the  change  is  made  earlier.  The  sticks  of  phosphorus 
are  removed  before  being  used  a  second  time. 
The  patentee  believes  it  will  be  found  advantageous  to  pass  the 
sulphurous  acid  and  ozone  into  a  column  filled  with  coke,  pumice- 
stone,  or  other  suitable  material,  before  they  pass  into  the  sulphu- 
ric acid  chamber.  He  obtains  the  sulphurous  acid  by  burning 
sulphur  in  the  ordinary  way. 
THE  QUALITATIVE  AND  QUANTITATIVE  DETERMINATION  OF 
IODINE,  AND  ITS  SEPARATION  FROM  BROMINE  AND  CHLO- 
RINE BY  MEANS  OF  BENZINE  AND  NITRATE  OF  SILVER. 
By  E.  Moride. 
Benzine  possesses  the  property  of  dissolving  iodine  wherever  it 
meets  with  it  in  a  free  state.  The  color  produced  by  this  solution 
is  bright  red,  which  becomes  deeper  in  proportion  to  the  amount  of 
iodine  contained  in  it.  When  exposed  to  the  air,  the  iodine  is  vola- 
tilized, and  the  solution  becomes  discolored. 
If  a  few  drops  of  nitrous  acid  be  put  into  a  liquid  containing 
an  alkaline  iodide,  and  after  the  mixture  is  effected  2  or  3  grms. 
of  benzine  be  added  to  it,  and  the  whole  strongly  agitated,  the  ben- 
zine soon  rises  to  the  surface  of  the  liquid,  exhibiting  a  magnifi- 
cent color,  arising  from  the  iodine  which  it  brings  with  it.  This 
reaction  renders  it  possible  to  determine  with  the  greatest  ease  the 
presence  of  1  milligrm,  of  iodine  in  5  litres  of  water.  Neither 
ether  nor  the  oils  of  lavender,  citron  or  turpentine,  furnish  under 
similar  circumstances  such  decisive  results. 
Chloroform,  employed  either  in  M.  Rabourdin's  method  or  in 
that  of  M.  Grange,  certainly  in  many  cases  readily  shows  the  pre- 
sence of  iodine  ;  but  its  sensibility  and  the  color  which  it  acquires 
are  far  from  being  so  conclusive  as  the  characters  offered  by  ben- 
zine. In  carefully  conducted  experiments,  I  have  been  able  in  this 
way  to  determine  the  presence  of  iodine  wherever  traces  of  it  were 
indicated  by  starch-paste,  and  the  employment  of  benzine  has 
always  appeared  to  me  to  furnish  most  satisfactory  results. 
I  will  add  to  these  observations,  that  if  by  means  of  benzine  we 
can  separate  extremely  small  quantities  of  iodine  from  water,  it  is 
also  very  easy  to  determine  these  quantities  by  nitrate  of  silver  or 
metallic  mercury. 
19 
