328         ON  THE  MANUFACTURE  OF  TARTARIC  ACID,  ETC. 
lime,  or  212  parts  of  nitrate  of  strontia,  or  260  parts  of  nitrate 
of  baryta,  or  172  parts  of  sulphate  of  lime,  to  every  188  parts 
by  weight  of  bitartrate  of  potash  previously  existing  in  the  crude 
argol,  crude  tartar,  or  impure  bitartrate  of  potash,  and  now  ex- 
isting as  tartrate  of  potash  in  solution.  The  solution  of  the 
salts  of  potash  thus  obtained,  being  separated  by  decantation 
from  the  tartrate  of  lime  and  tartrate  of  baryta,  may  be  evapo- 
rated and  crystallized.  The  impure  salts  of  potash  may  be 
purified  by  re-crystallization,  and  the  tartrate  of  lime,  or  tartrate 
of  baryta,  or  tartrate  of  strontia,  after  having  been  washed  with 
water,  may  be  decomposed  with  sulphuric  acid  in  the  same  manner 
as  tartrate  of  lime  is  now  decomposed,  and  tartaric  acid  be 
herefrom  obtained  by  crystallization.  Impure  bitartrate  of 
potash,  crude  argol,  or  crude  tartar,  is  to  be  neutralized  by  means 
of  sulphides  of  sodium,  as  after  mentioned,  and  tartrate  of  potash 
and  soda  thereby  obtained,  which  said  solution,  after  being  sepa- 
rated from  the  insoluble  impurities,  may  be  evaporated  and 
crystallized.  Having  obtained  a  solution  of  tartrate  of  potash 
and  soda,  by  dissolving  the  said  salt  in  water,  the  said  solution 
is  to  be  decomposed  by  means  of  chloride  of  calcium,  in  the  pro- 
portion of  112  parts  by  weight  of  chloride  of  calcium  to  every 
300  parts  by  weight  of  tartrate  of  potash  and  soda  employed. 
The  decomposition  of  the  mixed  solutions  may  be  effected,  by 
treating  the  same  contained  in  a  suitable  vessel,  the  resulting 
tartrate  of  lime  being  allowed  to  settle.  The  supernatant  solu- 
tion containing  chloride  of  sodium  and  chloride  of  potassium  is  to 
be  withdrawn,  and  by  evaporation  and  crystallization  chloride  of 
potassium  and  chloride  of  sodium  obtained.  Or  a  solution  of 
tartrate  of  potash  and  soda  may  be  decomposed  in  a  similar 
manner,  by  heating  the  same  with  sulphate  of  lime,  in  the  pro. 
portion  of  172  parts  by  weight  to  every  300  parts  by  weight  of 
tartrate  of  soda  and  potash  employed.  After  separating  the 
tartrate  of  lime  formed,  the  solution  containing  sulphate  of  potash 
and  sulphate  of  soda  is  to  be  evaporated,  and  these  salts  either 
obtained  together,  or  they  may  be  separated  byre-crystallization. 
In  order  to  separate  certain  soluble  impurities,  such  as  coloring 
matters,  existing  in  the  solutions  of  citrates  or  tartrates  of  am- 
monia, potash,  or  soda,  their  solutions  may  be  filtered  through 
filters  or  cisterns  containing  animal  charcoal,  or  animal  charcoal 
