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ARTIFICIAL  PRODUCTION   OF  SALTPETRE. 
REMARKS  ON  THE  ARTIFICIAL  PRODUCTION  OF  SALTPETRE. 
By  R.  Reichenbach. 
It  is  only  within  the  last  few  years  that  general  assent  has 
been  given  to  the  opinion  that  the  production  of  saltpetre  con- 
sists in  an  oxidation  of  ammonia,  determined  or  facilitated  essen- 
tially by  the  presence  of  alkaline  or  earthy  bases. 
The  occurrence  of  native  saltpetre  is  well  known  to  be  inti- 
mately connected  with  the  decay  and  disintegration  of  calcareous 
rocks,  especially  felspathic  limestone,  which  are  at  the  same  time 
more  or  less  rich  in  organic  remains,  and  consequently  contain 
a  certain  amount  of  nitrogenous  substance.  It  is  this  animal 
substance,  which  at  a  sufficient  temperature  suffers  chemical 
change ;  that  is  to  say,  passes  more  or  less  rapidly  into  putrefac- 
tive fermentation,  the  nitrogen  being  either  wholly  or  principally 
converted  into  carbonate  of  ammonia.  Under  ordinary  circum- 
stances, this  volatile  ammoniacal  salt  gradually  escapes  into  the 
atmosphere ;  but  when  generated  with  a  porous  mass  of  rock, 
which  admits  of  the  penetration  of  atmospheric  oxygen,  it  suffers 
a  partial  decomposition  and  oxidation  to  nitrate  of  ammonia  as 
well  as  nitrates  of  lime  and  potash. 
It  is,  moreover,  a  general  fact  that  whenever  animal  substance 
is  brought  into  immediate  contact  with  potash,  lime,  and  sand, 
and  the  whole  exposed  to  the  air,  there  is  an  abundant  formation 
of  nitrates,  and  this  observation  has  afforded  both  an  explanation 
of  the  mode  in  which  saltpetre  is  formed  spontaneously  and  a 
means  of  obtaining  it  artificially.  It  has  been  found  to  be  a  con- 
dition of  considerable  importance  that  the  heaps  of  substances 
prepared  for  the  production  of  nitric  acid  should  possess  a  certain 
degree  of  porosity,  so  that  a  very  large  surface  may  be  exposed 
to  the  air  absorbed. 
The  statement  of  these  few  facts  connected  with  the  artificial 
production  of  saltpetre  will  suffice  for  a  consideration  of  the  ques- 
tion. Whether  this  process  corresponds  to  the  present  state  of 
technical  chemistry,  or  whether  it  is  not  capable  of  great  improve- 
ment ?    On  examining  the  process  in  detail  it  will  be  found, 
1.  That  the  mixture  of  the  several  substances  is  generally  con- 
ducted with  too  much  irregularity  and  uncertainty,  so  that  it  is 
difficult  to  ascertain  whether  they  are  in  a  proper  proportion. 
