162 
BROMINE  AND  IODINE   IN  CHILI  NITRE. 
The  purification  was  effected  in  the  following  manner  : — The 
salt,  broken  into  pieces  about  the  size  of  peas,  was  briskly  agitated 
with  cold  water  for  a  few  seconds,  and  the  liquid  poured  quickly 
off  before  the  suspended  matter  was  deposited.  This  operation 
was  repeated  a  few7  times  until  the  salt  was  colorless,  when  it  was 
drained  upon  a  funnel  and  washed  with  pure  water  until  no  further 
reaction  with  silver  salt  was  given. 
GrOneberg  has  examined  the  liquid  which  flowed  spontaneously 
from  50  tons  of  raw  Chili  nitre  that  had  been  stored  in  a  damp 
place  and  the  mother-liquors  obtained  from  the  subsequent  purifica- 
tion of  this  nitre. 
He  first  proceeded  by  removing  from  these  liquors  as  much  as 
possible  of  the  crystallizable  salts,  chloride  of  sodium  and  nitrate 
of  soda.  During  the  evaporation  for  this  purpose  a  remarkable 
circumstance  presented  itself.  As  the  concentration  increased  the 
liquid  became  more  turbid  and  brown,  evolving  a  sensible  odor  of 
iodine,  and  when  treated  with  starch  gave  a  deep  blue  color. 
It  subsequently  appeared  that  this  was  owing  to  a  decomposition 
of  iodide  of  magnesium.  The  addition  of  caustic  soda  prevented 
this  inconvenience. 
When  the  liquids  had  been  concentrated  as  much  as  possible 
they  weighed  90  lbs.  The  iodine  was  separated  by  heating  with 
iron  filings  and  adding  gradually  sulphate  of  copper  as  long  as 
there  remained  any  iodine  or  iodic  acid  in  solution.  During  the 
precipitation  the  liquid  again  became  brown  from  the  liberation  of 
iodine.  By  this  action  of  sulphate  of  copper  upon  iodide  of  sodium 
—  2  (I  Na)  +  2  (Cu  O  S03)  there  were  produced  2  (Na  O  S03) 
+  Cu2  I  +  I.  The  brown  color  was,  however,  removed  by  the 
gradual  action  of  iron  filings,  for  from  1+2  Fe  +  2  (Cu  O,  S03) 
there  were  produced  2  (Fe  O  S03)  -f  Cu2 1,  so  that  all  the  iodine 
of  the  iodide  of  sodium  was  ultimately  converted  into  iodide  of 
copper/ while  the  iodine  of  the  iodates  w7as  contained  in  the  pre- 
cipitate as  proto-iodate  of  iron  and  iodate  of  copper. 
This  precipitate  washed,  dried,  and  mixed  with  broken  glass, 
to  render  it  more  porous,  was  treated  with  sulphuric  acid  and  oxide 
of  manganese.  On  distillation  the  action  was  at  first  violent,  and 
a  large  quantity  of  iodine  mixed  with  chloride  of  iodine  passed 
over.  The  water  into  which  the  product  of  distillation  passed  be- 
came brown  from  the  solution  of  chloride  of  iodine,  which  after  a 
