230 
MANUFACTURE  OF  AMMONIA,  ETC. 
passes  to  the  upper  boiler,  which  is  also  furnished  with  an  exit- 
pipe.  Into  the  lower  boiler  high-pressure  steam  is  passed,  which 
soon  causes  the  gas-liquor  to  boil,  and  the  vapor  of  ammonia  and 
water  passes  off  through  an  exit- pipe  into  the  boiler  placed  next 
above  it  in  the  series,  the  liquor  in  which  is  thus  also  brought  to 
boil,  the  vapor  of  ammonia  and  water  passing  off  from  it  in  the 
same  way  to  the  boiler  next  above  it,  and  so  on  throughout  the 
series.  By  the  time  the  vapor  of  ammonia  passes  off  from  the 
uppermost  boiler  it  has  become  so  concentrated,  that  on  passing 
it  into  sulphuric  or  muriatic  acid,  a  concentrated  solution  of  either 
of  those  salts  is  obtained,  of  sufficient  specific  gravity  to  crystal- 
lize without  evaporation,  and  thus  a  considerable  saving  in  fuel 
and  time  is  affected,  and  the  ammoniacal  gas-liquor  is  most 
thoroughly  exhausted.  Fresh  supplies  of  ammoniacal  liquor  are 
constantly  furnished  to  the  uppermost  boiler  from  the  reservoir ; 
whilst  the  partially  exhausted  liquors  are  run  from  the  higher  to 
the  lower  vessels  in  succession,  and  the  exhausted  liquors  run  off 
to  waste  from  the  lowermost  vessel  of  the  series.  As  the  gas- 
liquors  often  contain  some  fixed  ammoniacal  salts,  Mr.  Spence 
recommends  the  addition  of  lime  to  the  contents  of  the  boilers, 
in  order  to  render  free  the  ammonia  contained  in  such  salts. 
Mr.  Wilson  patented,  December  7th,  1850,  the  following  pro- 
cess of  obtaining  sulphate  of  ammonia  from  the  waste  products 
of  coke-ovens  and  other  furnaces.  Eor  this  purpose  he  employs 
the  following  apparatus  An  iron  column  lined  with  lead,  or  a 
brick  column  lined  with  fire-bricks  and  well  burnt  clay,  is  filled 
with  coke  or  round  pebbles  ;  this  column  has  an  area  or  cross 
section  five  or  six  times  that  of  the  chimney  connected  with  the 
coke-ovens,  and  is  from  twelve  to  fifteen  feet  in  height ;  at  the 
bottom  of  this  column,  which  can  be  supported  on  cross  bars,  is 
a  space  of  three  feet  left  clear,  in  which  is  placed  a  cistern,  con- 
structed of  the  same  materials  as  the  coliimn,  and  another  simi- 
lar cistern  is  placed  at  the  top  of  the  column,  its  bottom  being 
pierced  full  of  holes.  The  lower  cistern  is  then  filled  with  sul- 
phuric acid  so  diluted,  that,  when  saturated  with  ammonia,  it 
shall  not  form  a  solution  of  sufficient  density  to  cause,  on  evapo- 
ration by  the  heat  of  the  column,  an  incrustation  of  sulphate  of 
ammonia.  The  gaseous  products  of  combustion  are  then  made 
to  pass  through  the  lower  cistern  up  the  column  of  coke,  and  as 
