NITRE. 137 
with 500 tons of nitre annually, at given rates and prices 
in times of peace and war. 
In France this article is obtained in what are called 
nitrieres, or nitre beds. These consist of the refuse of 
animal and vegetable substances, which undergo putre- 
faction, mixed with calcareous and other earths ; and 
the nitre is obtained from them by water, as above- 
mentioned. The principal requisites for the formation 
of nitre are said to be lime, animal and vegetable mat- 
ters, heat, and an open, but not too free communication 
with dry atmospheric air. 
The discovery of gunpowder has completely changed 
the modern art of war. The earliest notice that has 
occurred respecting the use of this article in Europe is, 
that it was employed in the wars of Germany, some- 
what before the year 1373. It is said, however, to have 
been known in China long anterior to that period. Its 
component parts are nitre, charcoal, and sulphur, in 
the proportion of seventy-six, fifteen, and nine parts, in 
every hundred. These ingredients are first reduced to 
a fine powder separately, and then mixed with water, so 
as to form a thick paste. After this has dried a little, it 
is placed upon a kind of sieve full of small holes, through 
which it is forced. By this process it is divided into 
grains, the size of which depend of course upon the size 
of the holes through which it has been squeezed. It 
afterwards undergoes some other operations before it is 
ready for use. 
Nitre is frequently administered in medicine ; and it 
is used very extensively in different arts. A mixture of 
equal parts of nitre and tartar, burned together in a 
crucible, forms what is called 'white Jlux, which is used 
for melting and reducing different kinds of metallic sub- 
stances. And a mixture of one part of nitre and two 
parts of tartar burned in the same manner forms what is 
called black flux. Nitre possesses antiseptic qualities in 
a considerable degree, whence it is much used, in con- 
junction with common salt and bay salt, for the preserv- 
ing of animal food from putrefaction. 
