332         ON  THE  MANUFACTURE  OF  TARTARIC  ACID,  ETC. 
The  resulting  sulphite  or  sulphites  of  soda  and  hyposulphite  of 
soda,  which  are  obtained  in  this  operation,  may  be  dried  and  fused 
with  small  coal  or  charcoal,  and  converted  into  sulphide  of  sodium. 
Or  the  sulphite  or  sulphites  of  soda  and  the  hyposulphite  of  soda 
may  be  decomposed  in  a  suitable  vessel  by  sulphuric  acid,  and 
the  sulphurous  acid  liberated  be  collected  and  employed  for  pre- 
cipitating bitartrate  of  potash  from  tartrate  of  potash  and  soda. 
A  solution  of  tartrate  of  potash  and  soda,  obtained  as  before 
described,  by  neutralizing  bitartrate  of  potash  with  sulphide  of 
sodium,  or  from  any  other  source,  may  be  decomposed  with  bisul- 
phate  of  potash  or  bisulphate  of  soda,  or  acid  sulphates  of  potash, 
or  acid  sulphates  of  soda,  added  in  the  proportion  of  300  parts  by 
weight  of  tartrate  of  potash  and  soda  (in  crystals)  dissolved  in 
water,  to  every  40  parts  by  weight  of  sulphuric  acid  not  in  com- 
bination as  neutral  sulphate  of  potash  or  soda  ;  that  is  to  say — 
in  employing  bisulphate  of  potash,  300  parts  by  weight  of  tar- 
trate of  potash  and  soda  are  to  be  used  for  every  137  parts  by 
weight  of  bisulphate  of  potash,  and  300  parts  by  weight  of  tar- 
trate of  potash  and  soda  are  to  be  employed  for  every  121  parts 
by  weight  of  bisulphate  of  soda  (solid.) 
Having  dissolved,  in  any  suitable  vessel,  the  acid  sulphates  of 
soda,  a  solution  of  the  tartrate  of  potash  and  soda,  obtained 
as  before  mentioned,  is  to  be  added,  and  after  being  well 
agitated,  the  precipitated  bitartrate  of  potash  is  allowed  to  settle. 
The  supernatant  solution  is  then  to  be  separated,  and  saturated 
either  with  sulphide  of  sodium  or  carbonate  of  soda,  and  evapo- 
rated, in  order  that  the  sulphate  of  soda  may  be  separated  by 
crystallization  from  the  tartrate  of  soda  and  potash  existing  in 
the  said  solution.  The  tartrate  of  potash  and  soda  thus  obtained 
from  the  supernatant  liquor,  is  to  be  decomposed  with  a  solution 
containing  an  equivalent  proportion  of  acid  sulphate  of  soda,  and 
the  deposited  bitartrate  of  potash  separated. 
If  acid  sulphate  of  potash  be  employed  to  decompose  the  tar- 
trate of  potash  and  soda,  the  supernatant  solution,  having  been 
separated  from  the  precipitated  bitartrate  of  potash,  and  having 
been  neutralized  with  sulphide  of  sodium,  or  sulphide  of  potassium, 
or  carbonate  of  soda,  or  carbonate  of  potash,  is  to  be  evaporated, 
and  the  sulphate  of  potash  and  sulphate  of  soda  separated  from 
the  tartrate  of  potash  and  soda  by  crystallization.    The  tartrate 
