PROCESS  FOR  ANTIMONIATE  OF  POTASSA. 
71 
Indigo  burns  with  an  extremely  intense  white  light. 
Some  samples  of  commercial  iodine  left  a  slightly  reddish 
saline  mass ;  they  consequently  contained  manganese. 
Black  sulphuret  of  antimony  in  powder  burns  quietly  with  a 
yellowish  white  light. 
Dry  extract  of  logwood  burns  with  a  very  intense  light,  as  does 
also  gamboge,  with  evolution  of  a  black  smoke. 
Caoutchouc  burns  with  an  exceedingly  intense  light,  as  soon 
as  the  evolution  of  oxygen  begins  to  be  tolerably  strong  ;  great 
heat  is  evolved,  so  that  the  bottom  of  the  test-tube  is  not  un- 
frequently  melted. 
Tea-leaves  impart  to  the  mass  a  tolerably  strong  red  color, 
they  therefore  contain  manganese. — London  Chem.  Gfaz.,  Oct. 
15,  1857,  from  Buchners  Neues  Repert. 
NEW  PROCESS  FOR  PREPARING  ANTIMONIATE  OF 
POTASSA. 
This  process  consists  in  decomposing  golden  sulphuret  of  anti- 
mony with  pure  potassa  ley.  The  sulphuret  is  boiled  with  the 
ley,  which  gives  rise,  on  one  hand,  to  sulpho-antimoniate  of 
potassa  :  and  on  the  other,  to  the  antimoniate.  The  two  salts 
remain  in  solution,  owing  to  the  excess  of  ley  employed.  It  is 
boiled  with  recently  precipitated  hydrate  of  copper,  which 
changes  its  oxygen  for  the  sulphur  of  the  sulphuret  of  antimony, 
and  gives  rise,  on  the  one  hand,  to  sulphuret  of  copper,  and,  on 
the  other,  to  antimonic  acid,  and,  consequently,  to  antimoniate 
of  potassa.  The  operation  is  terminated  when  a  small  test  of 
the  liquor  is  no  longer  precipitated  black  by  acetate  of  lead. 
On  the  contrary,  the  precipitate  which  is  formed,  should  be  of  a 
beautiful  white. 
The  filtered  solution  then  contains  nothing  but  antimoniate  of 
potassa  ;  the  antimonic  acid  is  precisely  in  the  modification 
which  M.  Fremy  has  mentioned,  as  proper  for  precipitating  the 
salts  of  soda. 
In  using  this  reagent,  care  must  be  taken  to  operate  only  on 
alkaline,  or  at  any  rate  neutral  liquors.  With  acid  liquors,  a 
precipitate  is  indeed  produced,  but  this  precipitate  is  antimonic 
acid. 
