138 
MANUFACTURE   OF  AMMONIA,  ETC. 
of  sulphate  of  iron  or  manganese,  into  which  the  pipe  dips; 
another  pipe  passes  from  the  top  of  this  vessel  to  the  bottom  of  a 
second,  containing  dilute  sulphuric  acid-  The  liquor  being  put  in- 
to the  boiler,  heat  is  supplied,  and  the  hydrosulphate  of  ammonia, 
being  the  most  volatile  of  the  salts  contained  in  the  liquor,  passes 
over;  first  its  hydrosulphuric  acid  is  absorbed  by  the  contents  of 
the  first  vessel,  and  the  ammonia  by  the  acid  contained  in  the' 
second  vessel  with  the  formation  of  sulphate  of  ammonia.  After 
the  hydrosulphate  of  ammonia  has  all  passed  over,  the  liquor  re- 
maining in  the  boiler  may  be  drawn  off  and  neutralized  in  the  usual 
way  with  sulphuric  acid.  Or,  muriatic  acid  may  be  substituted 
for  sulphuric  acid  and  thus  muriate  of  ammonia  may  be  obtained. 
Mr.  Johnson  patented,  December  20,  1845,  a  method  of  obtain- 
ing ammoniacal  salts,  by  passing  coal-gas  in  its  way  from  the  re- 
torts to  the  gasometer,  through  vessels  containing  certain  metallic 
salts,  such  as  sulphate  of  iron  as  the  cheapest,  previously  pounded 
very  fine,  and  moistened  with  just  enough  water  to  bring  the  pul- 
verized salt  to  a  pasty  consistency.  Sulphate  of  ammonia  is  thus 
obtained. 
Mr.  Hills  patented  August  11,  1846,  the  following  processes 
relative  to  the  manufacture  of  ammoniacal  salts.  To  obtain  muri- 
ate of  ammonia  he  employs  muriate  of  magnesia,  which  he  either 
mixes  in  the  state  of  powder  with  the  coal  in  the  manufacture  of 
gas,  or  he  puts  it  in  a  small  iron  vessel  placed  within  the  same  re- 
tort, or  when  several  retorts  are  used  at  the  same  time,  one  retort 
may  be  used  to  contain  the  muriate  of  magnesia  alone  ;  in  either 
case  the  muriatic  acid  liberated  from  the  decomposition  of  the  mu- 
riate of  magnesia  by  means  of  heat  combines  with  the  ammonia  to 
form  muriate  of  ammonia  which  is  collected  in  the  ammoniacal  li- 
quor. 
In  the  same  patent  Mr.  Hills  describes  his  improved  apparatus 
for  obtaining  ammonia  from  ammoniacal  liquors.  This  apparatus 
is  similar  in  construction  to  a  condenser  which  is  in  common  use 
for  distillation  of  alcohol,  and  which  in  form  is  a  four-sided  vessel, 
furnished  with  shallow  pans  fixed  to  the  alternate  sides.  The  am- 
moniacal liquor  flows  through  pipes  placed  under  the  upper  shelves 
or  pans,  thus  keeping  them  cool  whilst  itself  receives  an  accession 
of  heat,  and  then  flows  into  the  top  pan  of  the  lowTer  series.  When 
this  top  pan  is  full,  the  liquor  flows  over  into  the  next  of  the  series, 
