ON  THE  MANUFACTURE  OF  TARTARIC  ACID,  ETC. 
333 
of  potash  and  soda  may  be  decomposed  in  a  similar  manner  by 
means  of  acid  sulphates  of  soda,  and  after  separating  the  depo- 
sited bitartrate  of  potash,  the  supernatant  solution  may  be  neu- 
tralized with  sulphides  of  sodium  or  carbonate  of  soda,  and  by 
crystallizing  the  resulting  sulphite  of  soda  and  hyposulphite  of 
soda,  obtained  by  evaporation  and  crystallization,  they  may  be 
decomposed  by  adding  an  equivalent  of  sulphuric  acid  to  a  solu- 
tion, or  to  crystals  of  sulphite  of  soda  or  hyposulphite  of  soda  con- 
tained in  a  suitable  vessel,  and  the  free  sulphurous  acid  liberated, 
collected  and  employed  for  decomposing  tartrate  of  potash  and 
soda  as  before  mentioned. 
Dr.  Price's  further  improvements  in  the  manufacture  of  bitar- 
trate of  potash,  relate  to  the  decomposition  of  tartrate  of  ammonia 
and  potash  by  means  of  acids  and  acid  salts,  so  as  to  obtain  puri- 
fied bitartrate  of  potash,  which  is  effected  as  follows :  Having 
obtained  a  solution  of  tartrate  of  potash  and  ammonia  in  the 
manner  before  described,  and  the  said  tartrate  of  potash  and 
ammonia  having  been  placed  in  a  suitable  vessel,  sulphurous  acid 
is  passed  into  the  same,  until  no  further  precipitation  of  bitar- 
trate of  potash  is  occasioned  on  the  addition  to  the  solution  of  a 
small  quantity  of  an  acid  stronger  than  tartaric  acid.  The  de- 
posited bitartrate  of  potash  being  separated*  the  solution,  con- 
taining sulphite  of  ammonia  and  bitartrate  of  potash  may  be 
decomposed  in  a  suitable  vessel,  By  means  of  sulphuric  or  hydro- 
chloric acid,  so  as  to  obtain  sulphurous  acid,  which  may  be  em- 
ployed for  effecting  the  decomposition  of  a  subsequent  quantity 
of  a  solution  of  tartrate  of  potash  and  ammonia.  The  resulting 
sulphate  of  ammonia  or  chloride  of  ammonium,  containing  in  solu- 
tion a  certain  amount  of  bitartrate  of  potash,  is  to  be  neutralized 
with  any  of  the  before  mentioned  volatile  alkaline  ammoniacal  salts, 
and  evaporated  ;  and  the  sulphate  of  ammonia  or  chloride  of  am- 
monium obtained  by  crystallization.  The  mother-liquors  con- 
taining tartrate  of  potash  and  ammonium  are  to  be  acidified  with 
sulphurous  acid,  in  order  to  obtain  bitartrate  of  potash.  The 
resulting  solution  is  then  neutralized  with  ammonia,  and  evapo- 
rated as  before  mentioned,  care  being  taken,  in  both  instances, 
that  the  solution  be  kept  slightly  alkaline  by  mean3  of  ammonia 
or  alkaline  ammoniacal  salts  during  and  after  concentration. 
The  tartrate  of  potash  and  ammonia  may  be  decomposed,  and 
