NIT

NIT

C 153 )

Sp.gr, of folution

Proportion of Nitre in

at 61 0 Fahr.

100 parts of folution.

1.132

- - - - - 21

1.138

1.145

. 2 3

1.152

- - - - - 24

1.158

- - - - - 25

If a faturated

folution of nitre is boiled

ftrongly, and more efpecially if the boilingtemperature is raifed by the addition of anydeliquefcent fait, a very notable proportion ofthe nitre is volatilized with the water, as willbe mentioned more particularly in the latterpart of this article.

Nitre is readily fufible at a heat almoft equalto that of melting zinc, or fomewhat belowignition, and may be kept for a confiderabletime at this temperature without undergoingany change, except a flight lofs of weight fromparting with its water of cryftallization; apiece of charcoal may even be immerfed in itwithout producing any detonation. Whenpoured out on any flat furface it prefently con-geals into a white tranflucent mafs, commonlyknown by the name of cryfal mineral . If how-ever the heat to which melted nitre is expofedbe greater than that requifite for maintaining itsliquidity, a decompofition begins to take place;bubbles of gas are difengaged,and by a high heat,continued as long as any air is extricated, theacid is entirely decompofed, and nothing but thealkaline bafe of the fait remains behind ; thegas that firft comes over during this procefs istolerably pure oxygen, but the latter portionsare largely mixed with azot. When this expe-riment is performed in an earthen crucible, thealkalization of the nitre takes place more fpeed-ily, on account of the affinity of the potaffi forthe filex and alumine of the crucible, hence alfoas the heat increafes a confiderable part of theacid is fet at liberty in a Hate of femi-decompo-fition, which accounts for the red fumes ofnitrous vapour obferved on this occafion byBeaume. When the fufion is not continuedlong enough for the total decompofition of the^itre, the refidue confifts of free alkali, anda variable proportion of nitrite of potafh.

The decompofition of nitre by heat is muchKiore fpeedy, if fome inflammable fubflance beprefent: in this cafe a rapid difengagement ofi. nn d ^eat ta ^ es place, accompanied by aloud hiding noife, which is called the detonationof nitre; the added inflammable matter com-bines with the greater part of the oxygen of the

VOX,. a.

nitric acid, and is itfelf converted into an oxydor acid; if the latter, it generally unites withthe alkaline bafe of the nitre in proportion asits own acid is decompofed or driven off. Thusif a few grains of fulphur be projected on red-hot nitre the former immediately takes fire,burns rapidly with a reddifh-puvple flame, andis converted into fulphuric and fulphureousacid, at the expence of the nitric acid, which ismore or lefs decompofed ; the fulphureous acidmixed with nitrous vapour flies off, while thefulphuric acid remains behind in combinationwith the difengaged potaffi of the nitre, formingfulphat of potaffi. When the quantity of ful-phur added is not fufficient to effect a totaldecompofition of the nitre, the refult is a mix-ture of the two neutral falts, and was knownamong the old chemifts by the name of Glnfer’spolychref fait.

If inftead of adding the fulphur by fmallparcels at a time to the nitre in fufion, the twoingredients are carefully mixed together in theproportion of five or fix parts of the former toone of the latter, and the furface be then touchedwith a hot iron or any other ignited body, thedetonation is much flower than in the formercafe, the nitric acid appears to be entirely de-compofed, and a quantity of Sulphuric Acid ,much more than fufficient to faturate the alkaliof the nitre, is produced.

The detonation of nitre with charcoal is veryrapid, whether the charcoal is added to thenitre brought previoufly to a ftate of fu/ion, orthe tw© ingredients are mixed together by pul-verization, and then thrown into a crucible orany other veffel heated red-hot; an intenfebluifh flame is difengaged, accompanied by greatheat and a white vapour, the nitric acid difap- .pears, and the refidual fait is fub-carbonat ofpotaffi. The rationale of this procefs is com-monly thus explained: the charcoal combineswith the oxygen of the nitric acid, and is itfelfconverted into carbonic acid, of which a portionunites with the alkaline bafe of the nitre, whilethe reft is volatilized together with the azotproduced by the decompofition of the nitricacid. From the experiments however of Mr.Davy e it appears, that the detonation of thefetwp fubftances is by no means a procefs of fuchfimplicity as is generally imagined. This ablechemift having filled a glafs tube with a mix-ture compofed of 6 parts of nitre and i ofcharcoal, detonated it, and received the produftin a jar inverted over mercury and containinga little water: after the operation the water

• Refeardies, p. 44.

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