• 
ARTIFICIAL  PRODUCTION  OF   SALTPETRE.  523 
2.  That  the  presence  or  preponderance  of  inorganic  substances, 
although  in  one  respect  unavoidable,  retards  the  progress  of  the 
putrefaction,  and  consequently  the  production  of  ammonia,  from 
which  alone  the  nitric  acid  is  formed,  and  it  is  probably  owing  to 
this  circumstance  that  the  artificial  production  of  saltpetre  goes 
on  with  such  remarkable  slowness. 
3.  The  uniform  maintenance  of  a  proper  temperature  is  not 
sufficiently  observed. 
4.  Since  it  has  become  evident  that  the  presence  of  ammonia 
is  the  essential  condition  of  the  formation  of  nitric  acid,  it  is 
possibly  not  necessary  to  produce  the  ammonia  by  putrefactive 
fermentation.  There  are  many  other  sources  from  which  it  might 
be  more  readily  obtained,  and  then  submitted  in  a  pure  state  to 
those  conditions  under  which  it  is  converted  into  nitric  acid,  and 
thus  the  whole  operation  would  be  simplified  and  rendered  inde- 
peadent  of  local  and  accidental  influences. 
When,  as  in  some  parts  of  the  continent,  the  production  of 
saltpetre  is  made  a  collateral  operation  of  agriculture,  in  which 
case  space  and  time  are  of  less  importance,  the  old  process  is 
sufficient.  But  the  case  is  different  when  it  is  required  to  pro- 
duce a  certain  large  quantity  of  saltpetre  annually. 
First,  then,  as  regards  the  present  process,  it  must  not  be  for- 
gotten in  the  mixing  of  the  substances  to  make  a  nitre  bed  that 
the  production  of  nitrate  of  potash  is  the  ultimate  object.  Conse- 
quently this  base  must  be  present  in  some  appropriate  form  and 
in  sufficient  quantity.  It  is  best  to  use  the  lime  in  the  caustic 
hydrated  state.  It  might  be  possible  to  produce,  in  the  first  in- 
stance, nitrate  of  lime  and  then  nitrate  of  potash  by  a  subsequent 
double  decomposition,  but  it  would  appear,  a  priori,  improbable 
that  the  lime  alone  would  be  so  effective  in  determining  the  for- 
mation of  nitric  acid  as  the  mixture  of  lime  and  potash.  This 
point  is  one  which  is  certainly  deserving  of  experimental  investi- 
gation. 
Assuming,  then,  that  ammonia  and  potash  are  the  two  sub- 
stances chiefly  necessary  for  the  production  of  saltpetre,  it  re- 
mains only  to  ascertain  the  precise  conditions  of  its  formation, 
and  to  ensure  an  adequate  supply  of  these  substances  so  as  to  be 
able  to  carry  out  the  fabrication  of  saltpetre  to  any  extent  and 
with  any  degree  of  rapidity. 
