MANUFACTURE  OF  AMMONIA,  ETC. 
229 
tion  of  gas-water,  guano,  or  any  other  matter  from  which  am- 
monia can  be  procured  by  destructive  distillation  with  quick- 
lime ;  the  ammoniacal  gas  being  purified  before  use  by  passing 
it  through  water. 
Michiel's  mode  of  obtaining  sulphate  of  ammonia,  patented 
April  30,  1850,  is  as  follows :  The  ammoniacal  liquors  of  the 
gas  works  are  combined  with  sulphate  and  oxide  of  lead,  which 
is  obtained  and  prepared  in  the  following  way :  Sulphuret  of 
lead  in  its  natural  state  is  taken  and  reduced  to  small  fragments 
by  any  convenient  crushing  apparatus.  It  is  then  submitted  to 
a  roasting  process,  in  a  suitably  arranged  reverberatory  furnace 
of  the  following  construction:  The  furnace  is  formed  of  two 
shelves,  or  rather  the  bottom  of  the  furnace  and  one  shelf,  and 
there  is  a  communication  from  the  lower  to  the  upper.  The 
galena  or  sulphuret  of  lead,  previously  ground,  is  then  spread 
over  the  surface  of  the  upper  shelf,  to  a  thickness  of  about  2  or 
2|  inches,  and  there  it  is  submitted  to  the  heat  of  the  furnace. 
It  remains  thus  for  about  two  hours,  at  which  time  it  is  drawn 
off  the  upper  shelf  and  spread  over  the  lower  shelf  or  bottom  of 
the  furnace,  where  it  is  exposed  to  a  greater  heat  for  a  certain 
time,  during  which  it  is  well  stirred,  for  the  purpose  of  exposing 
all  the  parts  equally  to  the  action  of  the  heat,  and  at  the  same 
time  the  fusion  of  any  portion  of  it  is  prevented.  By  this  pro- 
cess the  sulphuret  of  lead  becomes  converted,  partly  into  sul- 
phate and  partly  into  oxide  of  lead.  This  product  of  sulphate 
and  oxide  of  lead  is  to  be  crushed  by  any  ordinary  means,  and 
reduced  to  about  the  same  degree  of  fineness  as  coarse  sand.  It 
is  now  to  be  combined  with  the  ammoniacal  liquors,  when  sul- 
phate of  ammonia  and  sulphuret  and  carbonate  of  lead  will  be 
produced. 
In  order  to  obtain  sulphate  and  muriate  of  ammonia  with  the 
greatest  possible  economy,  Mr.  Spence  patented,  November  12. 
1850,  the  following  process:— A  series  of  two  or  more,  say  for 
instance  four  cylindrical  boilers  are  placed  at  such  a  distance, 
one  above  the  other,  that  the  contents  of  the  upper  boiler  may 
be  drawn  off  into  the  one  next  below  it.  Each  boiler  is  furnished 
with  a  cock,  to  allow  of  the  passage  of  the  contents  of  the  boiler 
from  one  to  the  other  throughout  the  series.  Each  of  these 
vessels  contains  gas-liquor,  from  a  reservoir  of  which  a  pipe 
