Besides saltpetre or the nitric acid, which is the active ingredient in saltpetre, there are various other acids, as the oxymuriatic, (chlorine of Davy), the hyper oxymuriatic, the arsenic, tunestic, molybdic, and columbic, that are powerful supporters of combustion. Of these the most easy of access is the oxymuriatic; and this has in consequence been tried either instead of, or in conjunction with, the nitric acid, to ascertain whether it be possessed of more power. The best experiments upon the subject are those of Edward Howard, Esq. as communicated to the Royal Society. The effect, according to these, is very singular, in the employment of the oxymuriat of potash, the only form in which the oxymuriatic acid has hitherto been made use of. It acts with considerably more energy so far as its range extends; but this range is far short of that produced by saltpetre, or nitrat of potash. It produces also a much more violent explosion; and an explosion which, in one instance, burst the vessel, and nearly destroyed the eye-sight of the bold and ingenious experimenter.

[Editor.

THERE

CHAP. XIV.

FULMINATING POWDERS.

HERE are various combinations under this name that possess a near resemblance to gunpowder in their constituent parts, easily inflame, and explode with great violence, but require a certain degree of heat to produce this effect. We shall notice the com. mon and the metallic fulminating powders.

SECTION I.

Common Fulminating Powder.

THIS is prepared as follows: take three parts of nitre, two of purified pearl-ash, and one of flowers of sulphur, mix the whole very accurately in an earthen mortar, and place it on a tile or plate before the fire, till it is perfectly dry: then transfer it while hot into a ground stopper bottle, and it may be kept without injury for any length of time. In order to experience its effects, pour from ten to forty grains into an iron ladle, and place it over a slow fire:

in a short time the powder becomes brown and acquires a pasty consistence; a blue lambent flame then appears on the surface, and in an instant after the whole explodes with a stunning noise and a slight momentary flash. If the mass be removed from the fire as soon as it is fused, and kept in a dry well-closed vial, it may at any time be exploded by a spark, in which case it burns like gunpowder, but more rapidly and with greater detonation; but this effect cannot be produced on the unmelted powder, how accurately soever the ingredients of it are mixed together. When fulminating powder is in fusion, but not heated to the degree necessary to produce the blue flame, a particle of ignited charcoal thrown upon it will occasion immediately a remarkably loud explosion.

It appears that the ingredients of this powder do not acquire their fulminating property till combined by fusion; in other words, till the pot-ash of sulphur form sulphuret of pot-ash: whence fulminating powder may also be made by mixing sulphuret of pot ash with nitre, instead of by adding the sulphur and alkali sepa

rate.

In all these the cause of the detonation, or fulmination, is not accurately understood. In simple fulminating powder, there is a very large portion of elastic gass evolved; in fulminating gold or silver, a much smaller; yet the explosion in the latter case is infinitely greater than that in the former.

Fulminating Gold.

Dissolve pure gold in nitro-muriatic acid to saturation, and di. lute the solution with three times its bulk of distilled water, and add to it gradually some pure ammonia; a yellow precipitate will be obtained, which must be repeatedly washed with distilled water, and dried on a chalk stone, or in a filter. When perfectly dry, it is called fulminating gold, and detonates by heat, as may be shewn by heating a few grains of it on the point of a knife over the candle.

Fulminating Silver.

Dissolve fine silver in pale nitric acid, and precipitate the solu tion by lime-water; decant the fluid, mix the precipitate with liquid ammonia, and stir it till it assumes a black colour; then de. cant the fluid, and leave it in the open air to dry. This product is fulminating silver, which when once obtained cannot be touched

without producing a violent explosion. It is the most dangerous preparation known, for the contact of fire is not necessary to cause it to detonate. It explodes by the mere touch. Its preparation is so hazardous, that it ought not to be attempted without a mask, with strong glass eyes, upon the face. No more than a single grain ought at any time to be tried as an experiment. This was invented by M. Berthollet.

M. Chenevix has invented a fulminating silver, not so dangerous as that just mentioned. It explodes only by a slight friction in contact with combustible bodies. It is thus prepared: diffuse a quantity of alumina through water, and let a current of oxygenated muriatic acid gass pass through it for some time. Then digest some phosphate of silver on the solution of the oxygenated muriate of alumina, and evaporate it slowly. The product obtained will be a hyper-oxygenated muriate of silver, a single grain of which, in contact with two or three of sulphur, will explode vio lently with the slightest friction.

Fulminating Mercury.

The mercurial preparations which fulminate, when mixed with sulphur, and gradually exposed to a gentle heat, are well known to chemists they were discovered, and have been fully described, by Mr. Bayen.

MM. Brugnatelli and Van Mons have likewise produced fulminations by concussion, as well by nitrat of mercury and phosphorus, as with phosphorus and most other nitrats. Cinnabar also is amongst the substances which, according to MM. Fourcroy and Vauquelin, detonate by concussion with oxymuriat of potash.

M. Ameilon had, according to M. Berthollet, observed, that the precipitate obtained from nitrat of mercury, by oxalic acid, fuses with a hissing noise.

But mercury, and most, if not all its oxyds, may, by treatment with nitric acid and alcohol, be converted into a whitish crystallized powder, possessing all the inflammable properties of gunpowder, as well as many peculiar to itself.

"I was led to this discovery," says Mr. Howard, the inventor, "by a late assertion, that hydrogen is the basis of the muriatic acid : it induced me to attempt to combine different substances with hydrogen and oxygen. With this view I mixed such substances with

alcohol and nitric acid as might (by predisposing affinity) favour as well as a'tract an acid combination of the hydrogen of the one, and the oxygen of the other. The pure red oxyd of mercury appeared not unnt for this purpose; it was therefore intermixed with alcohol, and upon both nitric acid was affused. The acid did not act upon the alcohol so immediately as when these fluids are alone mixed to. gether, but first gradually dissolved the oxyde: however, after some minutes had elapsed, a smell of ether was perceptible, and a white dense smoke, much resembling that from the liquor fumans of Libavius, was emitted with ebullition. The mixture then threw down a dark.coloured precipitate, which by degrees became nearly white. This precipitate I separated by filtration; and observing it to be crystallized in smaller acicular crystals, of a saline taste, and also finding a part of the mercury volatilized in the white fumes, I must acknowledge, I was not altogether without hopes that muriatic acid had been formed, and united to the mercurial oxide; I therefore, for obvious reasons, poured sulphuric acid upon the dried crystalline mass, when a violent effervescence ensued, and, to my great astonishment, an explosion took place. The singularity of this explosion induced me to repeat the process several times; and finding that I always obtained the same kind of powder, I prepared a quantity of it, and was led to make the series of experi ments which I shall have the honour to relate in this paper.

"I first attempted to make the mercurial powder fulminate by concussion; and for that purpose laid about a grain of it upon a cold anvil, and struck it with a hammer, likewise cold. It deto nated slightly, not being, as I suppose, struck with a flat blow; for upon using three or four grains, a very stunning disagreeable noise was produced, and the faces both of the hammer and the anvil were much indented.

"Half a grain, or a grain, if quite dry, is as much as ought to be used on such an occasion.

"The shock of an electrical battery, sent through five or six grains of the powder, produces a very similar effect. It seems, indeed, that a strong electrical shock generally acts on fulminating substances like the blow of a hammer. Messrs. Fourcroy and Vauquelin found this to be the case, with all their mixtures of oxymuriate of potass.

"To ascertain at what temperature the mercurial powder ex. plodes, two or three grains of it were floated on oil, in a capsule of

leaf tin; the bulb of a Fahrenheit's thermometer was made just to touch the surface of the oil, which was then gradually heated till the powder exploded, as the mercury reached the 368th degree.

"Desirous of comparing the strength of the mercurial compound with that of gunpowder, I made the following experiment in the presence of my friend Mr. Abernethy.

"Finding that the powder could not be fired with flint and steel, without a disagreeable noise, a common gunpowder proof, capable of containing eleven grains of fine gunpowder, was filled with it, and fired in the usual way the report was sharp, but not loud. The person who held the instrument in his hand felt no recoil; but the explosion laid open the upper part of the barrel, nearly from the touch-hole to the muzzle, and struck off the hand of the register, the surface of which was evenly indented, to the depth of 0.1 of an inch, as if it had received the impression of a punch.

"The instrument used in this experiment being familiarly known, it is therefore scarcely necessary to describe it: suffice it to say, that it was brass, mounted with a spring register, the moveable hand of which closed up the muzzle, to receive and graduate the violence of the explosion. The barrel was half an inch in calibre, and nearly half an inch thick, except where a spring of the lock impaired half its thickness.

"A gun belonging to Mr. Keir, an ingenious artist of CamdenTown, was next charged with seventeen grains of the mercurial powder, and a leaden bullet. A block of wood was placed at about eight yards from the muzzle to receive the ball, and the gun was fired by a fuse. No recoil seemed to have taken place, as the barrel was not moved from its position, although it was in no ways confined. The report was feeble; the bullet, Mr. Keir conceived, from the impression made upon the wood, had been projected with about half the force it would have been by an ordinary charge, or sixty-eight grains, of the best gunpowder. We therefore recharged the gun with thirty-four grains of the mercurial powder; and as the great strength of the piece removed any apprehension of danger, Mr. Keir fired it from his shoulder, aiming at the same block of wood. The report was like the first, sharp, but not louder than might have been expected from a charge of gunpowder. Fortunately Mr. Keir was not hurt; but the gun was burst in an extraordinary manner. The breech was what is called a patent