GENERATION  OF  AMMONIA. 
149 
ON  THE  GENERATION  OF  AMMONIA. 
By  A.  Vogel,  Jr. 
To  obtain  ammonia  in  the  gaseous  state,  its  concentrated 
aqueous  solution  is  usually  heated,  or  else  a  mixture  of  sal  am- 
monia with  lime.  It  is  evident,  that  in  both  cases  a  very  moist 
gas  must  be  obtained,  which,  if  a  dry  gas  is  wanted,  has  to  un- 
dergo a  drying  operation,  which  is  always  connected  with  con- 
siderable difficulties.  To  avoid  these,  it  has  been  proposed  to 
heat  the  mixture  of  sal  ammonia  and  powdered  lime  in  an  iron 
vessel  in  their  dry  state.  This  method  has  been  repeatedly  tried 
by  me,  when  I  was  convinced  that  it  had  no  advantage.  A  con- 
siderable temperature  is  required  to  completely  decompose  the 
sal  ammonia,  which,  in  the  form  of  vapor,  must  be  diffused 
through  the  lime,  and  if  it  is  not  entirely  free  of  organic  sub- 
stances, the  obtained  ammonia  is  empyreumatic.  In  the  follow- 
ing, I  give  a  method  entirely  different  from  the  former  ones, 
which  has  been  followed  for  some  time  for  the  generation  of  dry 
ammonia;  it  is  founded  on  the  observation,  that  a  solution  of 
chloride  of  calcium  in  aqua  ammonia,  boils  at  a  lower  point  than 
the  pure  liquor.  Experiments  have  shown,  that  liquor  ammonia 
saturated  with  chloride  of  calcium,  boils  at  80°  C,  (176°  F.,) 
and  if  diluted  with  an  equal  volume  of  water,  at  93°  C,  (199°  F.); 
by  addition  of  more  water,  the  boiling  point  rises  still  higher. 
In  this  fact  we  have  a  means  of  obtaining  gaseous  ammonia,  at 
a  temperature  far  below  the  boiling  point  of  wTater,  of  which 
much  less  is  evaporated  than  by  the  boiling  of  the  aqua  ammonia. 
To  a  concentrated  liquor  in  a  proper  flask,  chloride  of  calcium 
in  pieces  is  added  until  nothing  more  is  taken  up.  A  moderate 
heat  applied  by  a  small  spirit  lamp  immediately  causes  a  quick 
and  regular  generation  of  gas,  accompanied — provided  the  tem- 
perature be  regulated  with  care — by  very  little  water,  the 
greater  part  of  which  will  condense  in  the  receiver,  whilst  the 
last  traces  of  water  may  be  removed  by  passing  the  gas  through 
a  tube,  hardly  half  a  foot  in  length,  filled  with  pieces  of  caustic 
potassa.  If  prepared  according  to  the  old  methods,  even  by  ap- 
plication of  a  series  of  drying  tubes,  it  is  difficult  or  nearly  im- 
possible to  obtain  the  gas  perfectly  free  from  water. — Buchners 
K  Eepert.  f.  Pharm.,  1855,  244. 
