MANUFACTURE  OF  COMMERCIAL  CARBONATE  OF  AMMONIA.  135 
the  hydrosulphate  of  ammonia  contained  in  gas  liquors  into 
carbonate  of  ammonia  by  the  following  process : — A  mixture 
of  deutoxide  of  copper  and  charcoal,  or  other  form  of  carbon  in 
fine  powder,  in  the  proportion  of  twelve  parts  by  weight  of  the 
former  to  one  of  the  latter,  is  introduced  into  a  retort  made  red 
hot  and  furnished  with,  an  eduction  pipe  which  passes  through 
cold  water  and  finally  enters  into  the  gas  liquor.  The  forma- 
tion of  carbonic  acid  gas  soon  takes  place  by  the  union  of  the 
carbon  with  the  oxygen  of  the  metal,  and  this  gas  combining 
with  the  base  of  the  hydrosulphate  of  ammonia  converts  it  into 
carbonate,  with  liberation  of  sulphide  of  hydrogen.  When  the 
carbonic  acid  ceases  to  come  away,  nearly  all  the  carbon  will 
have  disappeared  from  the  retort,  and  the  oxide  of  copper  re- 
duced to  the  metallic  state.  The  charge  is  then  drawn,  and  left 
to  cool  while  a  second  charge  of  similar  materials  is  being 
worked  off ;  during  which  time  the  copper  reabsorbs  oxygen 
from  the  air,  and  becomes  again  deutoxide  of  copper,  which 
may  be  used  anew  with  fresh  carbon. 
Messrs.  Crane  and  Tullien,  in  their  patent  of  January  8, 
1848,  describe  a  method  of  manufacturing  ammonia  in  the  state 
of  carbonate,  hydrocyanate,  or  free  ammonia  by  passing  any  of 
the  oxygen  compounds  of  nitrogen,  together  with  any  com- 
pound of  hydrogen  and  carbon,  or  any  mixture  of  hydrogen 
with  a  compound  of  carbon,  through  a  tube  or  pipe  containing 
any  catalytic  or  contact  substance.  The  substance  which  is 
preferred  is  platinum  in  the  state  of  sponge,  or  asbestos 
coated  with  platinum.  This  is  to  be  placed  in  a  tube  and 
heated  to  about  600°  F.,  so  as  to  reduce  the  temperature  of  the 
product,  and  at  the  same  time  prevent  the  deposition  of  carbon, 
ate  of  ammonia,  which  passes  onward  to  a  vessel  of  the 
description  well  known  and  employed  for  the  purpose  of  con- 
densing carbonate  of  ammonia.  The  condenser  for  this  purpose 
must  be  furnished  with  a  safety  pipe,  to  allow  the  escape  of 
uncondensed  matter,  and  made  to  dip  into  a  solution  of  any 
substance  capable  of  combining  with  hydrocyanie  acid  or 
ammonia. 
Carbonate  of  ammonia  is  manufactured  at  the  present  time 
from  a  mixture  of  sulphate  or  chloride  of  ammonium  and 
