138  MANUFACTURE  OF  COMMERCIAL  CARBONATE  OF  AMMONIA. 
sublimation  is  going  on.  The  impure  carbonate  is  all  collected 
and  taken  to  the  resublimation  pans.  The  salt  is  put  into  iron 
tanks  about  sixteen  feet  long  and  two  and  a-half  deep  ;  they 
are  wider  at  the  bottom  than  at  the  top,  being  two  feet  seven 
inches  at  bottom  and  two  feet  at  top.  These  tanks  are  closed 
with  two  plates  of  iron  with  four  holes  in  each,  about  one  foot 
in  diameter  and  one  foot  apart  from  each  other.  Over  every 
hole  is.  placed  a  conical  leaden  vessel  with  a  flat  top.  These 
vessels  are  formed  of  a  sheet  of  lead,  and  the  two  ends  are  kept 
together  by  means  of  staples  and  wedges ;  a  circular  piece  of 
lead  is  luted  on  the  top  of  these  receivers  ;  the  height  of  them 
is  about  two  feet.  The  tanks  are  set  in  brickwork,  with  a  fire- 
place at  each  end.  They  are  charged  every  fortnight ;  a  certain 
quantity  of  water  is  first  put  in,  then  the  impure  carbonate. 
The  receivers  are  all  luted  on  over  their  respective  holes,  and  a 
small  fire  made  at  each  end  of  the  tank.  Great  care  is  required 
in  regulating  the  temperature,  because  the  heat  must  not  be 
too  high,  as  the  salt  sublimes  from  120°  to  130°  Fahrenheit. 
In  the  end  receiver  is  a  small  hole  closed  by  a  plug ;  on  taking 
this  out  it  can  be  seen  whether  the  temperature  is  too  high ; 
if  it  is,  the  fires  have  to  be  damped.  A  thermometer  is  gener- 
ally used,  but  some  people  prefer  to  trust  to  their  own  judg- 
ment. Instead  of  the  tank  and  fires  separate  pots  may  be  used, 
each  one  being  surmounted  by  a  leaden  cap ;  these  pots  are 
either  set  in  brickwork  and  heated  by  the  flue  of  the  retort 
furnace,  or  they  may  be  set  in  a  water  bath.  At  the  end  of 
fourteen  days  the  leaden  receivers  are  lined  with  a  thick  crust 
of  carbonate;  they  are  taken  down,  and  the  lead  stripped  off; 
the  outside  of  the  block  is  rather  dirty,  it  is  well  scraped,  and 
then  broken  into  pieces,  packed  in  jars,  and  sent  to  the  mar- 
ket. The  leaden  receivers  are  well  washed  and  re-shaped.  A 
small  quantity  of  the  residuary  liquor  is  taken  out  of  the 
tanks,  but  the  chief  part  is  left  in,  a  fresh'  charge  of  carbonate 
is  added,  the  receivers  are  luted  on,  and  the  operation  goes  on 
the  same  as  before. 
The  greatest  use  which  is  made  of  this  salt  is  by  bakers  and 
confectioners ;  it  is  largely  employed  in  medicine  and  in  the 
manufacture  of  smelling  salts. — Lond.  Chem.  News,  Dec.  29, 
1865. 
