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Chemical  Notes. 
Am.  Jour.  Pharos 
June,  1879. 
The  methods  for  the  separation  of  the  iodine  from  its  combinations 
in  the  mother  liquors  may  be  divided  essentially  into  three  classes. 
I.  The  mother  liquors,  after  the  crystallization  of  the  saltpetre,  without 
further  concentration,  are  treated  with  a  solution  of  sodium  sulphite,, 
of  strength  corresponding  to  the  amount  of  iodine  present  ;  the  iodine 
thus  separated  from  the  sodium  iodate  is  filtered  through  linen  cloth,, 
washed,  pressed  and  sublimed.  2.  The  mother  liquors  are  treated  with 
sodium  sulphite  or  bisulphite  until  the  precipitated  iodine  is  converted 
into  HI,  and  this  is  precipitated  as  copper  iodide  by  a  solution  of  copper 
sulphate  and  sodium  sulphite.  3.  The  percentage  of  iodine  is  increased! 
by  fractional  evaporation  and  crystallization  of  the  mother  liquors,  and 
then,  after  adding  the  calculated  amount  of  sodium  bisulphite,  the  iodine- 
is  distilled  off  from  the  acidified  liquor. — Dingier' s  Journal,  231,  p.  375. 
In  many  of  the  hand-books  reference  is  made  to  the  existence  of 
bichromates  of  baryta,  lime,  and  some  of  the  heavy  metals  as  well 
as  those  of  the  alkalies.  Ludwig  Schulerud  has  examined  this 
question,  and  has  studied  the  precipitates,  or  salts,  obtained  with  potas- 
sium chromate  and  bichromate  respectively,  in  solutions  of  barium,  lead, 
mercurous,  silver,  thallium  and  lithium  salts.  His  results  are  as  follows  : 
With  barium  salts — The  precipitate  obtained  with  potassium  bichro- 
mate was  slightly  darker  in  color  than  that  obtained  with  the  neutral 
chromate,  but  on  analysis  both  yielded  figures  corresponding  to  the 
formula  BaCr04. 
The  precipitate  obtained  by  potassium  bichromate  in  calcium  salts 
was  not  analyzed,  but  appeared  to  be  only  a  mixture  of  calcium  chro- 
mate and  free  chromic  acid. 
With  lead  salts — The  two  precipitates  showed  almost  no  difference 
in  color,  and  on  analysis  both  corresponded  closely  to  the  formula 
PbCr04. 
With  mercurous  salts — Only  the  precipitate  obtained  with  potassium 
bichromate  was  prepared  for  analysis.  It  showed  a  composition 
Hg2Cr04. 
With  silver  salts — Bichromate  of  potassium  produced  a  precipitate  of 
dark-red  crystalline  silver  bichromate.  Hot  water  extracts  from  this 
chromic  acid,  leaving  silver  chromate.  The  precipitate  obtained  showed 
the  composition  Ag2Cr2Or,  and  after  the  washing  gave  results  nearly 
corresponding  to  the  composition  Ag2Cr04. 
With  thallium  salts — Potassium  chromate  precipitates  clear  yellow 
