NITRE. 
NITRE. See Nitrates. Nitre is found 
abundantly on the surface of the earth, in 
India, South America, South Africa, and 
even in some parts of Spain. In Germany 
and France it is obtained by means of arti- 
ficial nitie-beds. These consist of the re- 
fuse of animal and vegetable bodies, under- 
going putrefaction, mixed with calcareous 
and other earths. It has been ascertained, 
that if oxygen gas be presented to azote at 
the instant of its disengagement, nitric acid 
is formed. This seems to explain the ori- 
gin of the acid in these beds. The azote, 
disengaged from these putrifying animal 
substances, combines with the oxygen of 
the air. Tiie potash is probably furnished, 
partly at least, by the vegetables and the 
soil. The nitre is extracted from these 
beds, by lixiviating the earthy matters with 
water. This water, when sufficiently im- 
pregnated, is evaporated, and a brown-co- 
loured salt obtained, known by the name 
of crude nitre. It consists of nitre, com- 
mon salt, nitrate of Hme, and yarions other 
salts. The foreign salts are either sepa- 
rated by repeated crystallizations, or by 
washing the salt repeatedly with small 
quantities of water ; for the foreign salts 
being more soluble, are taken up first. 
Nitre, when slowly evaporated, is obtained 
in six-sided prisms, terminated by six-sided 
pyramids ; but for most purposes, it is pre- 
ferred in an irregular mass, because in that 
state it contains less water. The specific 
gravity of nitre, as ascertained by Dr. Wat- 
son, is 1.9. Its taste is sharp, bitterish, and 
cooling. It is very brittle. It is soluble in 
seven times its weight of water, at the tem- 
perature of 60°, and in rather less than its 
own weight of boiling water. When ex- 
posed to a strong heat it melts, and congeals 
by cooling into an opaque mass, which has 
been called mineral crystal. Whenever it 
melts, it begins to disengage oxygen ; and, 
by keeping it in a red heat, about the third 
of its weight of that gas may be obtained : 
towards the end of the process azotic gas is 
disengaged. If the lieat be continued long 
enough, Ihe salt is completely decomposed, 
and pure potash remains behind. It deto- 
nates more violently with combustible bodies 
than any of the other nitrates. When mix- 
ed with one-third part of its weight of char- 
coal, and thrown into a red-hot crucible, or 
when charcoal is thrown into red-hot nitre, 
detonation takes place, and one of the most 
brilliant combustions that can be exhibited. 
The residuum is carbonate of potash. A 
still more violent detonation takes place, if 
phosphorus is used instead of charcoal. Ni- 
tre oxydizes all the metals at a red heat. 
The composition of nitre, according to Kir- 
wan, is 
100.0 
Nitre furnislies all the nitric 
acid in 
its states, employed either by chemists or 
artists : it is obtained by decomposing it 
by means of the sulphuric acid. When 
burnt with tartar, it yields a pure carbo- 
nate of potash. In tlie assaying of various 
ores it is indispensable, and is equally ne- 
cessary in the analysis of many vegetable 
and animal substances. But one ot the 
most important compounds, formed by 
means of nitre, is gunpowder, which has 
completely changed the modern art of war. 
The discoverer of this compound, and the 
person who first thought of applying it to 
the purposes of war, are unknown. It is 
certain, however, that it was used in the 
fourteenth century. From certain ar- 
chives, quoted by Wiegleb, it appears, that 
cannons were employed in Germany before 
the year 1372. No traces of it can be 
found in any European author, previous to 
the thirteenth century ; but it seems to 
have been known to the Chinese long be- 
fore that period. There is reason to be- 
lieve, that cannons were used in the battle 
of Cressy, which was fought in 1346. They 
seem even to have been used three years 
earlier at the siege of Algesiras ; but before 
this time, they must have been known in 
Germany, as there is a piece of ordnance at 
Amberg, on which is inscribed the year 
1303. Roger Bacon, who died in 1292, 
knew the properties of gunpowder; but it 
does not follow that he was acquainted with 
its application to fire-arms. See Gunpow- 
PER. When three parts of nitre, two parts 
of potash, and one part of sulphur, all pre- 
viously well dried, are mixed together in a 
warm mortar, the resulting compound is 
known by the name of fulminating powder. 
If a little of this powder be put into an 
iron spoon, and placed upon burning coals, 
or held above the flame of a candle, it gra- 
dually blackens, and at last melts. At tliat 
instant it explodes with a very violent re- 
port, and a strong impression is made upon 
the bottom of the spoon, as if it had been 
pressed down very violently. This sudden 
and violent combustion is occasioned by 
