ON  THE  MANUFACTURE  OF  TARTARIC  ACID,  ETC.  329 
may  be  mixed  with  their  solutions,  and  be  separated  together 
with  certain  impurities  by  filtration. 
As  bitartrate  of  potash  of  commerce  usually  contains  a  certain 
amount  of  tartrate  of  lime,  the  said  .tartrate  of  lime  will  remain 
with  the  impurities  after  the  before  mentioned  treatment  of  the 
said  bitartrate  of  potash,  and  in  order  to  utilize  the  same,  the 
residuum  is  to  be  treated  with  sulphuric  acid  in  the  same  manner, 
but  in  proportion  to  the  amount  of  tartrate  of  lime  present,  as 
the  tartrate  of  lime,  mixed  with  impurities  from  impure  bitartrate 
of  potash,  argols  or  tartars,  is  now  decomposed,  and  the  tartaric 
acid  therefrom  obtained. 
Mr.  Firmin's  combined  processes  of  obtaining  tartrate  of  lime 
for  the  manufacture  of  tartaric  acid,  purified  cream  of  tartar, 
and  binoxalate  of  potash,  are  practically  carried  out  in  the  fol- 
lowing way : — Into  a  vessel  such  as  is  used  in  the  manufacture 
of  tartaric  acid,  a  quantity  of  impure  bitartrate  of  potash  (argol 
or  tartar)  and  water  is  placed,  together  with  as  much  carbonate 
of  lime  as  will  suffice  to  neutralize  the  excess  of  acid  existing  in 
the  bitartrate.  By  this  means  neutral  tartrate  of  potash  is 
formed,  which  remains  in  solution,  and  tartrate  of  lime,  which 
precipitates  to  the  bottom  of  the  vessel.  The  solution  of  tartrate 
of  potash  is  decanted  from  the  tartrate  of  lime,  digested  on  animal 
charcoal,  and  filtered.  To  such  a  quantity  of  this  filtered  color- 
less solution,  as  is  found  by  analysis  to  contain  100  parts  of 
tartrate  of  potash,  60  parts  of  crystallized  oxalic  acid  (dissolved 
in  water),  or  as  much  as  will  serve  to  decompose  one  half  of  the 
tartrate  of  potash  contained  in  the  solution,  are  then  added.  By 
this  means,  a  neutral  solution  of  oxalate  of  potash  is  formed, 
remaining  in  solution,  whilst  the  tartaric  acid  liberated  unites 
with  the  other  half  of  the  tartrate  of  potash,  forming  pure  bitar- 
trate of  potash,  which  precipitates  to  the  bottom  of  the  vessel. 
In  the  ordinary  process  of  manufacturing  tartaric  acid,  in  which 
a  solution  of  tartrate  of  potash  is  decomposed  by  means  of  sul- 
phate of  lime,  a  quantity  of  solution  of  sulphate  of  potash  is 
obtained.  Mr.  Firmin  applies  this  solution  of  sulphate  of  potash, 
when  purified  and  filtered,  to  the  manufacture  of  binoxalate  of 
potash,  by  adding  to  as  much  of  this  solution  at  180°  F.  as  is 
found  by  analysis  to  contain  100  parts  of  sulphate  of  potash,  a 
solution  of  100  parts  of  crystallized  oxalic  acid,  or  a  sufficient 
