NITRIC 
this salt is now usually preparedj conform- 
ably to the directions of Boerliaave ; though 
in most dispensatories a tweuty-fourtli part 
of sulphur was directed to be deflagrated 
on the nitre, before it was poured out. 
This salt should not be left on the fire after 
it has entered into fusion, otherwise it will 
be converted into a nitrite of potash. If 
the heat be increased to redness, the acid 
itself is decomposed, and a considerable 
quantity of tolerably pure oxygen gas is 
evolved, succeeded by nitrogen. 
This salt powerfully promotes the com- 
bustion of inflammable substances. Two 
or three parts mixed with one of charcoal, 
and set on fire, burn rapidly; azote and 
carbonic acid gas are given out, and a small 
portion of the latter is retained by the al- 
kaline residuum, which was formerly called 
clyssus of nitre. Three parts of nitre, two 
of subcarbonate of potash, and one of sul- 
phur, mixed together in a warm mortar, 
Jorm the fulminating powder ; a small quan- 
tity of which, laid on a fire-shovel, and held 
over the fire till it begins to melt, explodes 
with aloud sharp noise. Mixed with sul- 
phur and charcoal it forms gunpowder. 
See Gunpowder. 
Three parts of nitre, one of sulphur, and 
one of fine saw-dust, well mixed, constitute 
what is called the powder of fusion. If a 
bit of base copper be folded up and cover- 
ed with this powder in a w'alnut shell, and 
the powder be set on fire with a lighted 
paper, it will detonate rapidly, and fuse 
the metal into a globule of sulphuret, with- 
out burning the shell. 
If nitrate of potash be heated in a retort, 
with half its weight of solid phosphoric or 
boracic acid, as soon as this acid begins to 
enter into fusion it combines with the potash, 
and the nitric acid is expelled, accompanied 
with a small portion of oxygen gas and 
nitric oxide. 
Silex, alumine, and barytes, decompose 
this salt in a high temperature by uniting 
with its base, as was observed when speak- 
ing of aqua fortis. The alumine will effect 
this even after it has been made into pot- 
teiy. 
The uses of nitre are various. Beside 
those already indicated, it enters into the 
composition of fluxes, and is extensively em- 
ployed in metallurgy : it serves to promote 
the combustion of sulphur in fabricating its 
acid; it is used in the art of dying; it is 
added to common salt for preserving meat, 
to which it gives a red hue ; it is an in- 
gredient in some frigprific mixtures; and 
ACID. 
it is prescribed in medicine, as coolii^, 
febrifuge, and diuretic, and some have re- 
commended it mixed with vinegar as a 
very powerful remedy for the sea scurvy. 
Nitj ate of soda, formerly called cubic or 
quadrangular nitre, approaches in its pro- 
peities the nitrate of potash; but differs 
from it in being somewhat more soluble in 
cold water, though less in hot, which takes 
up little more than its own weight; in 
being inclined to attract moisture from the 
atmosphere; and in crystallizing in rhombs, 
or rhomboidal prisms. It may be pre- 
pared by saturating soda with the nitric 
acid, by precipitating nitric solutions of the 
metals, or of the earths, except barytes, 
by soda : by lixiviating and crystallizing 
the residuum of common salt distilled with 
three-fourths its weight of nitric acid; or 
by saturating the mother waters of nitre 
with soda instead of potash. 
This salt has been considered as useless ; 
but professor Proust says, that five parts of 
it, with one of charcoal and one of sulphur, 
will burn three times as long as common 
powder, so as to form an oeconomical coni- 
position for fire- works. 
Nitrate of strontian may be obtained in 
the same manner as that of barytes, with 
which it agrees in the shape of its crystals, 
and most of its properties. It is much 
more soluble, however, requiring but four 
or five parts of water according to Vau- 
quelin, and only an equal weight according 
to Mr. Henry. Boiling wqter dissolves 
nearly twice as much as cold. Applied to 
the wick of a candle, or added to burning 
alcohol, it gives a deep red colour to the. 
flame. On this account it might be useful, 
perhaps, in thp art of pymtechny. 
Nitrate of lime, the calcareous nitre of 
older writers, abounds in the mortar of old 
buildings, particularly those that have been 
much exposed to animal effluvia, or pro- 
cesses in which azote is set free. Hence it 
abounds in nitre beds, as was observed 
when treating of the nitrate of potash. It 
may also be prepared artificially by pour- 
ing dilute nitric acid on carbonate of lime. 
If the solution be boiled down to a syrupy 
consistence, and exposed in a cool place, 
it crystallizes in long prisms, resembling 
bundles of needles diverging from a centre. 
These are soluble, according to Henry, in 
an equal weight of boiling water, and twice 
their weight of cold ; soon deliquesce on, 
exposure to the air ; and are decomposed 
at a red heat. Fonreroy says, tliat cold 
water dissolves four times its vyeiglit, an<\ 
