288
Book  II.
Division  II.
Tuaracters.
Properties.

SECONDARY  COMPOUNDS.
GENUS  III.  NITRATS.
THE  most  important  of  the  nitrats  have  been  long
known,  and  in  consequence  of  the  singular  properties
which  they  possess,  no  class  of  bodies  has  excited
greater  attention,  or  been  examined  with  more  unwearied ¬
  industry.  They  may  be  distinguished  by  the
following  properties  :
1.  Soluble  in  water,  and  capable  of  crystallizing  by
cooling.
2.  When  heated  to  redness,  along  with  combustible
bodies,  a  violent  combustion  and  detonation  is  produced. ¬

3.  Sulphuric  acid  disengages  from  them  fumes,  which
have  the  odour  of  nitric  acid.
4.  When  heated  along  with  muriatic  acid,  oxy-muriatic ¬
  acid  is  exhaled.
5.  Decomposed  by  heat  and  yield  at  first  oxygen  gas.
The  nitrats  at  present  known  are  12  in  number.  Few
of  them  combine  with  an  excess  of  acid  or  of  base,  so
that  there  are  hardly  any  supernitrats  or  subnitrats.
Sp.1.  Nitrat  of  Barytes.
THIs  salt  was  formed  immediately  after  the  discovery
of  barytes.  Vauquelin  has  lately  added  considerably  to
our  knowledge  of  its  properties.
It  is  usually  prepared  by  dissolving  native  carbonat
of  barytes  in  nitric  acid,  or  by  decomposing  sulphuret
of  barytes  by  means  of  nitric  acid,  and  evaporating  the
filtered  solution  till  the  nitrat  crystallizes.
Its  crystals  are  regular  octahedrons,  and  often  they
adhere  to  each  other  in  the  form  of  stars.  Sometimes