Nitre furnishes the nitric acid in all its states, it is obtained by decomposing it by means of the sulphuric acid. When burnt with tartar, it yields a pure carbonate of potash. In the assaying of various ores it is indispensable, and is equally necessary in the analysis of many vegetable and animal substances. But one of the most important compounds formed by means of nitre is gunpowder. See Nitric acid.

NITRIC acid. The two principal constituent parts of our atmosphere, when in certain proportions are capable, under particular circumstances, of combining chemically, into one of the most powerful acids, the nitric, which consists, according to Mr. Davy, of 705 of oxygen, and 29.5 of azote, or nitrogen. If these gases be mixed in this propertion in a glass tube, about a line in diameter over mercury, and a series of electric shocks be passed through them for some hours, they will form nitric acid; or, if a solution of potash be present with them, nitrate of pot ash will be obtained. For all practical purposes, however, the nitric acid is ob tained from nitrate of potash, from which sexpelled by sulphuric acid.

Four parts of pure nitrate of potash coarsely powdered, are to be put into a glass retort, and three parts of concentrated sulphuric acid cautiously added, taking care to avoid the fumes that arise. Join to the retort a tubulated receiver of large capacity, with an adopter interposed, and lute the junctures with a mixture of pipe-clay, sifted sand, and cut tow. In the tubular fix with fat lute a glass tube terminating in another large receiver, in which is a small quantity of water, and, if you wish to collect the gaseous products, let a bent glass tube from this receiver communicate with a pneumatic trough. Apply heat to the receiver by means of a sand bath. The first product that passes into the receiver is generally red and faming; but the appearances gradually diminish, till the acid comes over pale, and even colourless, if the materials used were clean.

In the large way, and for the purposes of the arts, extremely thick cast iron or earthen retorts are usually employed, to which an earthen head is ad ipted and connected with a range of proper condensors. The strength of the acid too is varied, by putting more or less water in the receivers. The nitric acid thus made generally contains sulphuric acid, and al80 muriatic from the impurity of the nitrate employed. If the former, a soluton of nitrate of barytes will occasion a white precipitate: if the latter, nitrate of silver will render it milky. The su! phuric acid may be separated by a second distiliation from very pure nitre; equal in weight to an eighth of that originally em ployed; or by precipitating with nitrate of brytes, decanting the clear liquid, and distilling it. The muriatic acid may be separated by proceeding in the same way

with nitrate of silver, or with litharge, decanting the clear liquor, and redistilling it, leaving an eighth or tenth part in the retort. The acid for the last process should be condensed as much as possible, and the redistillation conducted very slowly.

As this acid still holds in solution more or less nitrous gas, it is not, in fact, nitric acid, but a kind of nitrous: it is therefore necessary to put it into a retort, to which a receiver is added, the two vessels not being luted, but merely joined by paper; and to apply a very gentle heat for se veral hours, changing the receiver as soon as it is filled with red vapours. The ni trous gas will thus be expelied, and the nitric acid will remain in the retort, as limpid and colourless as water. It should be kept in a bottle secluded from the light, otherwise it will lose part of its oxy. gen.

Nitric acid should be of the specific gravity of 1.5, or a little more, and colourless. It boils at 248 deg, and may be distilled without any essential alteration. Exposed to the air it absorbs moisture, If two parts be suddenly diluted with one of water, the temperature will rise to about 112deg. but the addition of more water to this diluted acid will lower its temperature. It retains its oxygen with little force, so that it is decomposed by ali combustible bodies. Brought into contact with hydrogen gas at a high temperature, a violent detonation ensues; so that this must not be done withou: great caution. It inflames volatile oils, when suddenly poured on them: but to perform this experiment with safety, the acid must be poured out of a bottle tied to the end of a long stick, otherwise the operator's face and eyes will be greatly endangered. If it be poured on perfectly dry charcoal powder, it excites combustion, with the emission of copious fumes. By boiling it with sulphur it is decomposed, and its oxygen uniting with the sulphur forms sulphuric acid.

The nitric acid is of considerable use in the arts, it is employed for etching on copper; as a solvent of tin to form with that metala mordant for some of the fi. nest dyes; in metallurgy and assaying; in various chemical processes on account of the facility with which it parts with oxygen and dissolves metals; in medicine as a tonic, and as a substitute for mercurial preparations in syphylis and affections of the liver, as also in the form of vapour to destroy contagion. For the purposes of the arts it is commonly used in a diluted state, and contaminated with the sulphuric and muriatic acids, by the name of aqua fortis. This is generally prepared by mixing common nitre with an equal weight of sulphate of iron, and half, its weight of the same sulphate calcined, and distilling the mixture or by mixing nitre with twice its weight of dry powdered clay, and distilling in a reverberatory furnace. Two kinds are found in the shops, one called double aqua fortis, which is about half the strength of ni.. tric acid; the other simply aqua fortis, which is half the strength of the dou

ble.

A compound made by mixing two

1

those already indicated, it enters into the composition of fluxes, and is extensively employed 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 meaf, to which it gives a red hue; it is an ingredient in some frigorific mixtures; and it is prescribed in medicine, as cooling, febrifuge, and diuretic, and some have recommended it mixed with vinegar as a very powerful remedy for the sea scurvy.

Nitrate of soda, formerly called cubic or quadrangular nitre, approaches in its properties 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 prepared by saturating soda with the nitric acid, by precipitating ni tric solutions of the metais, 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 may be used in the composition for fire-works.

Nitrate of strontian may be obtained in the same manner as that of barytes. 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

night be useful, perhaps, in the art of py. rotechay.

Nitrate of lime, the calcareous nitre of oder writers, abounds in the mortar of old buildings, particularly those that have been much exposed to animal effluvia, or processes in which azote is set free. It may be prepared artificially by pouring lute nitric acid on carbonate of lime. I the solution be boiled down to a syrupy consistence, and exposed in a cool place, it chrystallizes in long prisms, resembling bundles of needles diverging froma centre. It might be employed instead of the nitrate of potash for manufacturing aqua fortis.

The nitrate of ammonia possesses the property of exploding, and being totally decomposed, at the temperature of 600 deg; whence it acquired the name of nitrum flammans. The readiest mode of preparing it, is by adding carbonate of ammonia to dilute nitric acid till saturaton takes place. If this solution be evapo rated in a heat between 70 deg. and 100 deg., and the evaporation not carried too far, it chrystallizes in hexaedral prisms terminating in very acute pyramids: if the heat rise to 212 deg., it will afford, on cooling, long fibrous silky chrystals. Nitrate of magnesia, magnesian nitre, chrystallizes in four-sided rhomboidal prisms, with oblique or truncated summits, and sometimes in bundles of sinall needles. Its taste is bitter, and very similar to that of nitrate of lime, but less pungent. It is fusible, and decomposable by heat, giving out first a little oxygen gas, then nitrous oxide, and lastly nitric acid. It deliquesses slowly. It is soluble

in an equal weight of cold water, and inbut little more hot.

The two preceding species are capable of combining into a triple salt, an ammog niaco-magnesian nitrate, either by unitinthe two in solution, or by a partial de composition of either by means of the bas of the other. This is slightly inflammable when suddenly heated and by a lower heat is decomposed, giving out oxygen azote, more water than it contained, ni trous oxide, and nitric acid. The residuum is pure magnesia. It is disposed to attract moisture from the air, but is much less deliquescent than either of the salts that compose it; and requires eleven parts of water at 60 deg. to dissolve it. Boiling water takes up more, so that it will chrystallize by cooling. It consists of 78 parts of nitrate of magnesia, and 22 of nitrate of ammonia.

From the activity of the nitric acid as a solvent of earths in analysation, the nitrate of glucine is better known than any other of the salts of this new earth. Its form is either pulverulent or a tenacious or ductile mass. Its taste is at first saccharine, and afterwards astringent. It melts, its acid is decomposed into oxygen grows soft by exposure to heat, soon and azote, and its base alone is left behind. It is very soluble, and very deliquescent.

Nitrate, or rather super nitrate, of alumine, crystallizes, though with difficulty, in thin, soft, pliable flakes. It is of an austere and acid taste, and reddens blue vegetable colours. It may be formed by dissolving in diluted nitric acid, with the assistance of heat, fresh precipitated alumine, well washed, but not dried. It is deliquescent, and soluble in a very small portion of water. Alcohol dissolves its own weight. It is easily decomposed by heat.

Nitrate of zircone was first discovered by Klaproth. Its crystals are small, ca pillary, silky needles. Its taste is astringent. It is easily decomposed by fire, very soluble in water, and deliquescent. It may be prepared by dissolving zircone in strong nitric acid; but like the preceding species, the acid is always in ex

cess.

Nitrate of yttria may be prepared in a similar manner. Its taste is sweetish, and astringent. It is scarcely to be obtained in crystals; and if it be evaporated by too strong a heat, the salt becomes soft like honey, and on cooling concretes into a stony mass. Exposed to the air it deli

quesces.

NITRITES. Though these salts are composed of nitrous acid and certain bases, yet the only way of obtaining them is by exposing a nitrate to a pretty strong heat, till a quantity of the oxygen gas is disengaged from it: what remains is 3 ni trite. These salts are, in general, deli quescent, very soluble in water, decomposable by heat, and by exposure to the air they are gradually converted into ai trates by absorbing oxygen.

NITROGEN. See Gas.

NITROUS acid. There is no such thing properly speaking, as nitrous acid, or the nitric base acidified with a minimum dose

NONCONFORMISTS, the same with

dissenters.

NOSTOCK, the name of a vegetable substance, of a greenish colour, partly transparent, and of a very irregular figure. I trembles at the touch, like jelly, but does not melt like that. It is found in all, but most frequently in sandy soils, usually after rain in summer.

NOSTRILS, in anatomy, the two aper tares or cavities of the nose, through which the air passes, and which serve to convey odours, and to carry off the pituita separated in the sinuses of the base of the

cranium.

NOT guilty, the general issue or plea of the defendant in any criminal action or prosecution; as also in an action of respass, or upon the case for deceits and wrongs.

NOVEL assignment, or new assignment, a term in law pleadings. In actions of trespass, where the form of the declaration being very general, the defendant pleads in bar a common justification; to which the plaintiff replies by stating, that he brought his action as well for a certain other trespass which he states with more particularity, as for that which is justified. This is called a new assignment.

NOVEMBER, the 11th month of the Julian year, consisting of thirty days: it got the name of November, as being the ninth month of Romulus's year.

NOUN, in grammar, a part of speech, which signifies things without any rela tion to time; as a man, sweet, &c.

NOURISHMENT. See Physiology. NUDE contract, nudum pactum, a bare promise without any consideration.

NUISANCE, signifies generally any thing that does hurt, inconvenience, or damage to the property or person of another. Nuisances are of two kinds, public and private, and either affect the public or the individual. The remedy for a private nuisances by action on the case for damages, and for a public nuisance by indictment. it must be done without riot, if at all. Every continuance of a nuisance is a fresh nuisance, and a fresh

action will lie.

NUL tiel record, the replication which the plaintiff makes to the defendant when the latter pleads a matter of record in bar to the action, and it is necessary to deny the existence of such record.

NUMBER, a collection of several units, or of several things of the same kind, as 2, 3, 4, &c. Number is unlimited in respect of increase; but in respect of deerease it is limited; unity being the first and least number.

NUMBERS, kinds and distinctions of. Mathematicians considering number un der a great many relations, have established the following distinctions. Broken

numbers, are the same with fractions. See Arithmetic. Cardinal numbers, are those which express the quantity of units, as 1, 2, 3, 4, &c. whereas ordinal numbers are those which express order, as ist, 2d, 3d, &c. Compound number, one divisible by some other number besides unity; as 12, which is divisible by 2,3,4, and 6. Numbers, as 12 and 15, which have some common measure besides unity, are said

to be compound numbers among tên selves. Cubic number, is the product a square number by its root: such s as being the product of the square num ber 9, by its root 3.

Determinate number, is that referred to some given unit, as a ternary or thee: whereas an indeterminate one, is that re ferred to unity in general, and is called quantity. Homogeneal numbers, are those referred to the same unit; as thes referred to different units are teribed he terogeneal. Whole numbers are other wise called integers. Rational number is one commensurable with unity; as a number, incommensurable with unity, s termed irrational or a surd. In the same manner a rational whole number is that whereof unity is an aliquot part; a ti tional broken number, that equal to sale aliquot part of unity; and a rational max ed number, that consisting of a whole number and a broken one. Even num ber, that which may be divided into two equal parts without any fraction, as 6, 12, &c. An evenly even number, is that which may be measured, or divided, without any remainder, by another even number, as 4 by 2. An unevenly even number, when a number may be equaly divided by an uneven number, as by 5. Uneven number, that which exceeds an even number, at least by unity, of which cannot be divided into two equal parts, 3, 5, &c. Primitive, or pome numbers, are those only divisible by usi ty. Prime numbers among thenselves, are those which have no comm measure besides unity. Perfect cumber, that whose aliquot parts added together make the whole number. Imperfect num bers, those whose aliquot parts, seed together, make either more or less this the whole. These are distinguished into abundant and defective; an instance in the former case, is 12, whose ahquot parts 6, 4, 3, 2, 1, make 16; and in the latter case 16, whose aliquot parts 8,4,2 and 1, make but 15. Plain number, at arising from the multiplication of ro numbers, as 6, which is the product of 3 by 2; and these numbers are called the sides of the plane. Square number, is the product of any number muaphed by itself: thus 4, which is the factum of 2 by 2, is a square number. Polygonal, or poly gonous numbers, the sums of arithmetical progressions beginning with unity, these, where the common difference is, 1, are called triangular numbers; where 3, square numbers; where 3, pentagonal numbers; where 4 hexagonal numbers; where 5, heptagonal numbers, &C. Pyramidal numbe. s, the sums of polygona numbers, collected after the same inan ner as the polygons themselves, and not gathered out of arithmetical progressions, are called first pyramidal numbers: the sums of the first pyramidals are calle second pyramidals, &c. If they arise out of triangular numbers, they are called triangular pyramidal numbers, if out of pentagons, first pentagonal pyramdals. From the manner of summing up pale gonal numbers, it is easy to conceive has the prime pyramidal numbers are found,

VIZ.

G. N. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19