132 
MANUFACTURE  OF  AMMONIA,  ETC. 
chloride  of  manganese  and  salts  of  zine,  may  be  obtained  by  the 
same  means. 
Mr.  Croll  thus  describes  his  peculiar  mode  of  manufacturing  or 
reproducing  the  salts  by  the  double  decomposition  of  salt  and  the 
residuum  and  precipitates  of  chloride  of  manganese  : — To  twelve 
ounces  of  the  dry  precipitate,  add  one  pound  of  common  salt,  mix 
them  intimately  together,  and  submit  them,  in  a  suitable  furnace, 
to  a  heat  scarcely  perceptible  in  the  dark,  for  two  or  three  hours  ; 
then  to  140  pounds  of  this  mixture  add  forty  gallons  of  water.  It 
is  then  fit  to  be'  used  for  purifying  gas  from  ammonia,  and  the  re- 
siduum which  the  gas  leaves  in  passing  through  it  is  to  be  heated 
in  like  manner.  The  insoluble  part  of  the  solution  before  mem- 
tioned  may  be  brought  to  its  original  state  by  dissolving  it  in  the 
acid  forming  one  of  its  constituents,  or  dissolving  it  in  sulphuric  or 
muriatic  acid,  by  which  means  a  sulphate  or  muriate  of  ammonia 
is  obtained.  In  Mr.  Waterton's  patent,  dated  August  27,  1840, 
for  the  manufacture  of  muriate  of  ammonia,  two  methods  of  effect- 
ing the  proposed  object  are  there  described.  The  first  consists 
in  making  a  saturated  solution  of  common  salt  in  water,  and 
mixing  with  it  a  quantity  of  finely  pulverized  carbonate  of  am- 
monia, about  equal  in  weight  to  the  salt  contained  in  the  solu- 
tion. The  mixture  is  agitated  in  a  close  vessel  for  six  or  eight 
hours,  and  as  much  carbonic  acid  gas  is  passed  therein  as  it 
will  absorb  (but  the  introduction  of  this  gas  is  not  absolutely  ne- 
cessary, although  the  patentee  prefers  it,)  the  liquid  is  then  sepa- 
rated from  the  solid  matter  by  filtration  aad  pressure.  The  solid 
matter  is  chiefly  bicarbonate  of  soda,  and  the  liquid  holds  in  solu- 
tion muriate  and  carbonate  of  ammonia  and  common  salt,  and  some- 
times a  small  portion  of  the  bicarbonate  of  soda- 
The  liquid  is  now  placed  in  a  distilling  vessel,  and  the  carbon- 
ate of  ammonia  being  distilled  over  into  a  suitable  receiver,  a  so- 
lution of  muriate  of  ammonia  and  common  salt  remains  in  the  still. 
This  solution  is  evaporated  by  heat  to  such  a  consistency  as  will 
cause  the  separation  of  the  common  salt  by  crystallization,  and  the 
salt  thus  crystallized  is  separated  from  the  liquid  by  any  conve- 
nient method.  The  liquid  is  then  evaporated  until  it  attains  the 
proper  specific  gravity  for  crystallizing,  and  it  is  transferred  into 
suitable  vessels  for  that  purpose.  The  crystals  produced  by  these 
means  are  nearly  pure  muriate  of  ammonia,  and  when  pressed  and 
