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IMPROVEMENTS  IN  MANUFACTURE  OF  IODINE. 
PATENT  GRANTED  TO  LOUIS  FAURE,  FOR  IMPROVEMENTS  IN 
THE  PROCESS  OF  MANUFACTURING  IODINE. 
This  invention  consists  in  the  application  and  mode  of  applying 
sulphurous  acid  and  chlorine  to  extracting  iodine  from  the  mother- 
liquors  of  nitrate  of  soda,  and  also  from  native  nitrate  of  soda. 
The  following  is  the  mode  of  treating  native  nitrate  of  soda 
and  the  mother-liquors  therefrom,  for  extracting  iodine  therein 
contained  in  the  state  of  iodic  acid  combined  with  soda,  lime,  or 
any  other  base Take  about  one  quart  of  the  mother-liquor  of 
nitrate  of  soda  of  the  strength  of  36°  to  37°  Beaume,  and  pour 
thereon,  in  small  quantities,  sulphurous  acid  held  in  solution  in 
water  from  a  graduated  test-glass,  continually  agitating  it  until 
the  precipitate  of  iodine  freely  separates  from  the  liquid.  When 
the  liquid,  which  is  slightly  shaded,  is  filtered,  it  instantly  loses 
its  color,  and  gives  no  sign  of  a  further  precipitate  of  iodine  on 
the  addition  of  1  drop  of  sulphurous  acid.  This  test  should  be 
repeated  upon  about  10  quarts,  and  if  the  two  results  obtained 
correspond,  500  to  1000  quarts  of  mother-liquor  can  confidently 
be  treated  ;  for  which  it  is  merely  necessary  to  employ  a  suitable 
proportion  of  sulphurous  acid,  and  a  vessel  capable  of  containing 
a  little  more  than  three  cubic  feet  of  liquid. 
The  vessel  to  be  employed  should  be  of  a  circular  form,  and 
made  of  non-porous  bricks,  well  luted,  and  afterwards  lined  with 
hydraulic  cement.  The  diameter  of  the  upper  part  of  the  vessel 
should  be  considerably  less  than  that  of  the  lower  part,  and 
should  be  hermetically  closed  by  means  of  a  wooden  lid,  well  ad- 
justed and  lined  internally  with  sheets  of  glass.  The  liquor  is 
to  be  agitated  in  this  vessel  by  means  of  a  vertical  shaft  or  agi- 
tator, provided  with  paddles,  and  set  in  motion  by  a  winch  and 
bevil-wheels.  The  paddles  are  inclined,  and  made  of  sandstone, 
and  disposed  for  agitating  violently  the  mother-liquors  when  the 
addition  of  sulphurous  acid  is  made. 
When  the  globules  of  gas  which  maintain  part  of  the  iodine 
precipitate  on  the  surface  of  the  liquor  have  been  dispelled,  the 
liquor  is  allowed  to  rest,  and  the  supernatant  liquor  is  then  with- 
drawn by  means  of  a  sandstone  siphon.  The  liquor  is  afterwards 
concentrated  to  extract  the  nitrate  and  sulphate  of  soda  and 
chlorides  of  sodium  and  potassium. 
The  iodine  precipitate  is  transferred  to  a  sandstone  fountain, 
