ON  THE  MANUFACTURE  OF  TARTARIC  ACID,  ETC.  325 
of  lime,  and  on  the  subsequent  decomposition  of  this  salt  by 
means  of  sulphuric  acid,  the  tartaric  acid  set  free  is  contaminated 
by  the  presence  of  these  foreign  matters,  and  the  manufacturer 
is  obliged,  as  in  the  case  of  citric  acid,  to  resort  to  several  crys- 
tallizations in  order  to  obtain  the  whole  of  the  acid  in  a  state  fit 
for  the  market. 
Dr.  Price's  improvements  in  the  manufacture  of  tartaric  acid 
consist  in  combining  bitartrate  of  potash  with  ammonia,  so  as  to 
form  tartrate  of  ammonia  and  potash,  which  may  be  effected, 
either  by  neutralizing  impure  bitartrate  of  potash  or  crude 
argol  or  crude  tartar  with  gas-liquor  or  with  a  solution  of  ammo- 
nia, or  with  carbonate  of  ammonia,  or  sulphides  of  ammonium, 
obtained  by  decomposing  tartrate  or  citrate  of  ammonia  with 
hydrated  caustic  lime  or  carbonate  of  lime,  or  sulphides  of  cal- 
cium, or  sulphides  of  barium  or  strontium,  or  with  condensed 
volatile  salts  of  ammonia,  obtained  by  distilling  gas-liquor  or 
ammoniacal  liquors.  Impure  bitartrate  of  potash  being  placed, 
with  or  without  water,  in  a  suitable  and  convenient  vessel,  a  so- 
lution of  ammonia  or  of  salts  of  ammonia  is  added  until  the 
whole  of  the  bitartrate  of  potash  existing  in  the  crude  tartar  or 
argol  is  neutralized,  and  a  solution  obtained  of  tartrate  of  potash 
and  ammonia,  which  solution  is  to  be  separated  by  filtration  or 
decantation  from  any  insoluble  impurities.  The  solution  of  tar- 
trate of  potash  and  ammonia,  thus  obtained,  may  be  treated  by 
either  of  the  following  processes  : — To  the  tartrate  of  potash  and 
ammonia  a  solution  of  chloride  of  calcium  is  added,  until  the 
whole  of  the  tartrate  of  potash  and  ammonia  is  decomposed ; 
that  is  to  say,  that  for  every  188  parts  of  bitartrate  of  potash 
existing  in  the  crude  argol  or  tartar,  and  now  existing  in  solution 
as  tartrate  of  potash  and  ammonia,  a  solution  of  chloride  of  cal- 
cium, corresponding  to  112  parts  of  chloride  of  calciun,  are  to 
be  added,  with  application  of  heat  to  the  mixed  solutions.  The 
solution  of  chloride  of  potassium  and  ammonium  is  separated 
from  the  tartrate  of  lime  produced,  by  decantation  or  filtration, 
and  the  solution  containing  chloride  of  potassium  and  chloride 
of  ammonium  is  to  be  evaporated,  care  being  taken  that  the  so- 
lution be  kept  alkaline  or  neutral  by  the  addition  of  either  of  the 
above  mentioned  ammoniacal  salts  or  ammonia.  The  tartrate  of 
lime  deposited,  during  the  evaporation  is  to  be  separated,  and 
