322  ON  THE  MANUFACTURE  OF  CITRIC  ACID,  ETC. 
Into  crude  lemon  or  lime-juice,  or  other  solution  containing  citric 
acid,  the  volatile  compounds  contained  in  gas-liquor  are  distilled 
until  the  said  juice  or  solution  is  neutralized,  or  the  said  juice 
or  solution  is  neutralized  -with  gas-liquor,  or  with  ammonia  or  its 
carbonates,  or  with  sulphides  of  ammonium,  obtained  as  hereafter 
described ;  and  the  neutralized  solution,  being  filtered  from  the 
insoluble  impurities,  the  solution  of  citrate  of  ammonia  thus  ob- 
tained, is  decomposed  in  the  following  manner: — The  solution  is 
placed  in  a  distillatory  apparatus,  and  to  it  there  is  added  150 
parts  by  weight  of  carbonate  of  lime,  powdered,  and  made  into  a 
paste  with  water,  or  90  parts  by  weight  of  lime  slacked,  and  made 
into  milk  of  lime,  to  every  192  parts  by  weight  of  citric  acid 
existing  in  solution  as  citrate  of  ammonia.  Heat  is  then  applied, 
and  the  said  solution  of  citrate  of  ammonia  is  decomposed  into 
citrate  of  lime  and  into  carbonate  of,  or  free,  ammonia,  which 
may  be  conducted  into  a  fresh  quantity  of  lemon  or  lime-juice,  or 
other  solution  containing  citric  acid,  so  as  to  neutralize  the  same, 
which  solution,  when  neutral,  or  better  when  alkaline,  may  be  treat- 
ed as  last  described.  The  citrate  of  lime,  thus  obtained,  is  to  be 
decomposed  with  sulphuric  acid,  as  is  now  done  in  the  ordinary 
manufacture  of  citric  acid,  and  the  solution  of  the  liberated  citric 
acid  filtered  from  the  sulphate  of  lime,  evaporated  and  crystallized. 
The  solution  of  citrate  of  ammonia,  obtained  as  first  above  de- 
scribed, may  be  treated  with  either  chloride  of  calcium  or  sulphate 
of  lime.  For  this  purpose  the  solution  of  citrate  of  ammonia  is 
boiled  with  either  of  the  salts  of  lime,  viz.,  chloride  of  calcium  or 
sulphate  of  lime,  until  the  citrate  of  ammonia,  previously  existing 
in  solution,  is  decomposed,  and  citrate  of  lime  and  either  sulphate 
of  ammonia  or  chloride  of  ammonium  obtained,  the  decomposition 
of  the  said  citrate  of  ammonia  being  conducted  in  the  same  man- 
ner and  with  the  same  precautions  as  after  described,  with  refer- 
ence to  improvements  in  the  manufacture  of  tartaric  acid. 
The  solution  of  citrate  of  ammonia,  obtained  as  first  above 
described,  may  be  decomposed  with  sulphide  or  sulphides  of  cal- 
cium, or  soda  waste  (oxysulphide  of  calcium,)  or  sulphide  of 
barium,  or  of  strontium,  the  said  solution  being  contained  in  a 
distillatory  apparatus,  and  the  decomposition  being  conducted  in 
the  manner  before  described. 
The  citric  acid  existing  in  lemon-juice,  or  other  solution,  may 
be  combined  with  potash  or  soda  instead  of  ammonia,  and  the 
