MANUAL, &c.
Before we enter into the practical part of Pyrotechny, we deem it consistent with the nature of our Work to give an ample description of the materials made use of; for we do not take it for granted that all our readers arechemists, or that they are sufficiently versed in that science to render such description unnecessary. But before the principles of the art can be well understood, or successfully applied, it is proper that the artist should possess a portion ofchemicalandmechanicalknowledge; the first will teach him to select his materials with judgment, to free them from impurities, and combine them in the proportions most suitable for eachparticular purpose; and the latter will assist him in constructing his different pieces so as to produce the desired effect with the least loss of time and force. Themechanical apparatuswe shall defer describing till they come immediately under hand, and such protraction we think will be conducive to a better understanding of their utility: and, in some other Section, we shall teach him to calculate the direction which the flying fire-works (from their principles of construction) are to move, and the velocity with which they are to proceed.
Gunpowder is the principal ingredient made use of in Pyrotechny; and, being of itself a compound, we shall make it the first object of description, and endeavour to point out the cause of every property it possesses.
The invention of it is ascribed, by Polydore Virgil, to a chemist, who accidentally put some of the composition, viz. nitre, sulphur, and charcoal into a mortar, and covered it with a stone, when it happened to take fire, and, what was a natural (though unexpected) consequence of such combination, it shattered the stone to pieces.
Thevet says, the person here spoken of was a monk of Fribourg, named Constantine Anelzen; but Belleforet, and other authors, with more probability, suppose him to be Bartholdus Schwartz, or the Black, who discoveredit, as some say, about the year 1320; and the first use of it is ascribed to the Venetians in the year 1380, during the war with the Genoese; and it is said to have first been employed in a place anciently called Fossa Clodia, now Chioggia, against Lawrence de Medicis; and that all Italy made complaints against it, as a manifest contravention of fair warfare.
But this account is contradicted, and Gunpowder shewn to be of an earlier era, for the Moors, when they were besieged in 1343 by Alphonsus XI. King of Castile, are said to have discharged a sort of iron mortars upon them, which made a noise like thunder; and this assertion is seconded by what Don Pedro, bishop of Leon, relates of King Alphonsus, who reduced Toledo, viz. “that in a sea-combat between the King of Tunis, and the Moorish King of Seville, about four hundred and fifty years ago, those of Tunis had certain iron tubes or barrels, wherewith they threw thunder-bolts of fire.â€
Farther, it appears that our Roger Bacon knew of Gunpowder near a hundred years before Schwartz was born. That excellent friar tells us, in his treatise, “De Secretis Operibus Artis & Naturæ, & de Nullitate Magiæ,†that from salt-petre, and other ingredients, we are able to make a fire that shall burn at what distance we please; andthe writer of the life of Friar Bacon says, that Bacon himself has divulged the secret of this composition in a cypher, by transposing the letters of the two words in chap. xi. of the above-cited treatise, where it is thus expressed;“sed tamen salis petrælura mope can ubre, (i. e. carbonum pulvere) et sulphuris; et sic facies tonitrum & corruscationem, si scias artificium:â€and from hence Bacon’s biographer apprehends the wordscarbonum pulverewere transferred to the sixth chapter of Dr. Longbain’s MS. In this same chapter Bacon expressly says, that sounds like thunder,and coruscations, may be formed in the air, much more horrible than those that happen naturally. He adds, that there are many ways of doing this, by which a city or an army might be destroyed; and he supposes that, by an artifice of this kind, Gideon defeated the Midianites with only three hundred men, (Judges, chap. 7th.) There is only another passage to the same purpose, in his treatise “De Scientia Experimentalia:†see Dr. Jebb’s edition of the Opus Magus, p. 474. Mr. Robins apprehends (see the preface to his Tracts,) that Bacon describes Gunpowder, not as a new composition first proposed by himself, but as the application of an old one to military purposes, and that it was known long before this time.
Dr. Jebb, in his preface to the above-citedwork, describes two kinds of fire-works; one for flying, inclosed in a case or cartouche, made long and slender, and filled with the composition closely rammed, like our modern rocket, and the other thick and short, strongly tied at both ends, and half filled, resembling our cracker; and the composition which he prescribes for both, is two pounds of charcoal, one pound of sulphur, and six pounds of salt-petre, well powdered and mixed together in a stone mortar.
Mr. Dutens in his “Inquiry into the Origin of the discoveries attributed to the moderns,†carries the antiquity of Gunpowder much higher; and refers to the accounts given by Virgil, Hyginus, Eustathius, Valerius Flaccus, and many other writers of the same date.
To close this tedious detail, we will mention one more work, which seems to confirm the antiquity of this composition, viz. the “Code of Gentoo Laws,†1776; in the preface of which it is asserted, that Gunpowder was known to the inhabitants of Hindostan, far beyond all periods of investigation.
Having said thus much concerning the history and antiquity of this wonderful composition, it remains for us to describe the method by which it is now manufactured: but to retain thatgradatum, or progressive order, with which we commenced our Work, itis necessary that we first describe the ingredients of which it is composed; for it is only by a knowledge of the parts of any composition, that we can gain a good understanding of the properties of the whole.
There are only three ingredients that enter into the composition of Gunpowder; these are Salt-petre, Sulphur, and Charcoal. The first is a combination of Nitric Acid[1]and Potash,[2]and is better known in modern chemistry by the name of Nitrate of Potash. The second is a substance very well known, from the inflammable properties it possesses; it is found alone, or combined with other bodies, in various situations; in volcanic productions it is found almost in its last degree of purity: it is found also, in the state of sulphuric acid; that is to say, combined with oxygen: it is found in this state in argil,[3]gypsum,[4]&c. and it may be likewise extracted from vegetable substances and animal matter. The third and last, is an article so well known in commerce, that it is almost needless to describe it; we shall therefore only observe, that the Charcoal found to be best for the composition of Gunpowder, is that made from the alder, willow, or black dog-wood.
This powerful composition is a mixture of these three ingredients, combined in the following proportions: for each 100 parts of Gunpowder, salt-petre 75 parts, sulphur 10, and charcoal 15. In some countries, the proportions are somewhat different; but this is the combination made use of by most of the English manufacturers.
The salt-petre is either that imported from the East Indies, or that which has been extracted from damaged Gunpowder. It is refined by solution, filtration, evaporation, and crystallization; after which it is fused, taking care that too much heat is not employed, or there is danger of decomposing the nitre.
The sulphur used is that which is imported from Sicily, and is refined by melting andskimming; the most impure is refined by sublimation.
The charcoal is made in the following manner. The wood is first cut into pieces of about nine inches in length, and put into an iron cylinder placed horizontally. The front aperture of the cylinder is then closely stopped: at the other end there are pipes connected with casks. Fire being made under the cylinder, the pyro-ligneous acid[5]comes over. The gas escapes, and the acid liquor is collected in the casks: the fire is kept up till no more gas or liquid comes over, and the carbon[6]remains in the cylinder.
The three ingredients being properly prepared, are ready for manufacturing. They are first separately ground into a fine powder, then mixed in the proper proportions, and afterwards committed to the mill for the purpose of incorporating their component parts. The powder-mill is a slight wooden building, with a boarded roof, so that in case of accidental explosions, the roof may fly off without difficulty, and in the least injurious direction, and thus be the means of preserving the other parts of the building.
The operative parts of the mill consist of two stones placed vertically, and running on another placed horizontally, which is called the bed-stone, or trough. On this bed-stone, about forty or fifty pounds of the composition are spread out, and moistened with water till reduced to about the consistency of a very stiff paste: after the stone-runners have made the proper revolutions over it, which requires about eight hours continued action of the mill, which is worked sometimes by horses, and sometimes by water, it is then taken from the mill, and sent to the corning-house, to be corned or grained. Here it is formed into hard lumps, and these are put into circular sieves, with parchment bottoms, perforated with holes of different sizes, and fixed in a frame connected with a horizontal wheel. Each of these sieves is also furnished with arunner or spheroid of lignum vitæ, which, being set in motion by the action of the wheels, forces the paste through the holes of the parchment bottom, forming grains of different sizes. The grains are then separated from the dust by sieves and reels made for that purpose. The grains are next hardened, and the rougher edges are taken off by shaking them for some time in a close reel, moved in a circular direction with a proper velocity.
When the powder has been corned, dusted, and glazed, it is dried in the stove-house, where great care should be taken to avoid explosion. The stove-house is a square apartment, three sides of which are furnished with shelves or cases, on proper supports, arranged round the room; and the fourth contains a large cast-iron vessel, called a “gloom,†which projects into the room, and is heated from the outside, so that no part of the fuel may touch the powder. For greater security against sparks by accidental friction, the glooms are covered with sheet-copper, and are always cool when the powder is put in or taken out of the room.
Here the grains are thoroughly dried, losing in the process what remains of the water added to the mixture in the mill, for bringing it to a working stiffness. A method of drying powder, by steam-pipes running roundand crossing the apartment, has been successfully tried; and thus the possibility of any injurious accident from over-heating is prevented. The temperature of the room, when heated in the common way by a gloom-stove, is always regulated by a thermometer hung in the door of the stoves.
If Gunpowder is injured by damp in a small degree, it may be recovered by again drying it in a stove; but if the ingredients are decomposed, the nitre must be extracted by boiling, filtering, evaporating, crystallizing, &c. and then, with fresh sulphur and charcoal, to be re-manufactured.
There are several methods of proving and trying the goodness and strength of Gunpowder. The following, as common methods, are frequently made use of. 1, By sight; for if it be too black, it is too moist, or has too much charcoal in it; so also if rubbed upon white paper, it blackens it more than good powder does. 2, By touch; for if in crushing with your finger-ends, the grains break easy, and turn into dust, without feeling hard, it has too much charcoal in it; or if in pressing under your fingers upon a smooth, hard board, some grains feel harder than the rest, or, as it were, dent your finger-ends, the sulphur is not well mixed with the nitre, and the powder is bad. And also by burning, in which method, little heaps of powder arelaid on white paper three or four inches asunder, and one of them fired; which, if the flame ascend rapidly, and with a good report, leaving the paper free from white spots, and without burning holes in it, and if sparks fly off and set fire to the adjoining heaps, the quality of the powder may be safely relied on; but if otherwise, it is either badly made, or the ingredients are impure.
These are some from among the common methods made use of for this purpose; but for greater accuracy in determining the relative strength of Gunpowder, various machines have of late been invented by men connected with military affairs. That excellent mathematician and philosopher, C. Hutton, LL.D. F.R.S. and late Professor of Mathematics in the Royal Military Academy, Woolwich, has constructed a machine for this purpose, which, for convenience and accuracy, far surpasses any thing of the kind hitherto invented. It is called Eprouvette, or a Gunpowder Prover, (for plans and description see third vol. Hutton’s Tracts, page 153;) and from its possessing so many peculiar advantages, is now generally used. It consists of a small cannon, the bore of which is about one inch in diameter, suspended freely like a pendulum, with the axis in a horizontal direction. This being charged with the proper quantity of powder, which is usually about two ounces, and thenfired, the gun swings or recoils backward, and the instrument itself shews the extent of the first or greatest vibration, which indicates the strength to the utmost nicety. The whole machine is so simple, easy, and expeditious in its use, that the weighing of the powder is the greatest part of the trouble; and it is also so uniform with itself, that the successive repetitions or firings with the same quantity of the same kind of powder, hardly ever yield a difference of the hundredth part from the first vibration.
Having thus given an account of almost every thing necessary to be known in regard to the process of making and ascertaining the relative strength of Gunpowder, we shall close this article with a few observations (which will be selected from the best authorities) on the physical causes of its inflammation and exploding. When the several ingredients of Gunpowder are properly prepared, mixed, and grained, in the manner already described, if the least spark be struck thereon from a steel and flint, the whole will be immediately inflamed, and burst out with extreme violence.
The effect is not hard to account for: the charcoal part of the grains whereon the spark falls, catching fire like tinder, the sulphur and nitre are ready melted, and the former also breaks into flame; and at the same time thecontiguous grains undergo the same fate.—Now it is known that salt-petre, when ignited, rarefies to a prodigious degree. Sir Isaac Newton reasons thus on the subject: “the charcoal and sulphur in Gunpowder easily take fire, and kindle the nitre; and the spirit of the nitre, being thereby rarefied into vapour, rushes out with an explosion much after the manner that the vapour of water rushes out of an æolipils; the sulphur also, being volatile, is converted into vapour, and augments the explosion: add, that the acid vapour of the sulphur, namely, that which distils under a bell into oil of sulphur, entering violently into the fixed body of the nitre, lets loose the spirit of the nitre, and excites a greater fermentation, whereby the heat is farther augmented, and the fixed body of the nitre is also rarefied into fume; and the explosion is thereby made more vehement and quick.â€
For if salt of tartar be mixed with Gunpowder, and that mixture be warmed till it take fire, the explosion will be greatly more violent and quick than that of Gunpowder alone, which cannot proceed from any other cause than the action of the vapour of Gunpowder upon the salt of tartar, whereby the salt is rarefied.
The explosion of Gunpowder arises, therefore, from the violent action whereby all themixture being quickly and vehemently heated, is rarefied and converted into fume and vapour; which vapour, by the violence of that action, becomes so hot as to shine, and appear in the form of a flame.
Another cause of the effects of Gunpowder, may be owing to the sudden formation of a quantity of gas, and are consequently greater when the gas is confined in all directions but one, as in our guns and cannons. The nitric acid of salt-petre is decomposed, and affords the gas. The other ingredients dispose it to be easily inflamed, which is necessary to the decomposition of the acid. Dr. Ingenhousy accounts for the effect of Gunpowder by observing that nitre yields by heat a surprising quantity of pure dephlogisticated air, and charcoal a considerable quantity of inflammable air; the fire employed to inflame the powder extricates these two airs, and sets fire to them at the instant of their extrication.
Count Rumford is of opinion that the force of the elastic fluid, generated in the combustion of Gunpowder, may be satisfactorily accounted for upon the supposition that its force depends solely on the elasticity of watery vapour or steam.
M. de la Hire, in the history of the French Academy for 1702, ascribes all the force and effect of Gunpowder to the spring or elasticityof the air inclosed in the several grains thereof, and in the intervals or spaces between the grains, the powder being kindled sets the springs of so many little parcels of air playing, and dilates them all at once, whence the effect; the powder itself only serving to light a fire which may put the air in action, after which the whole is done by the air alone.
Dr. Hutton seems to differ from the opinion of M. de la Hire, in regard to the expansion of inflamed gunpowder. Is it, he observes, occasioned by the air interposed between its grains, or by the aqueous fluid which enters into the composition of the nitre? We doubt much (continues he) whether it be the air, as its expansibility does not seem sufficient to explain the phenomenon; but we know that water, when converted into vapour by the contact of heat, occupies a space 14,000 times greater than its original bulk, and that its force is very considerable.
The same learned author says, that the discovery of the true cause of the expansive force of fired Gunpowder, is chiefly due to the English philosophers, and particularly to the learned and ingenious Mr. Robins. This author apprehends that the force of fired gunpowder consists in the action of a permanently elastic fluid, suddenly disengagedfrom the powder by the combustion, similar in some respects to common atmospheric air, at least as to elasticity. He shewed, by satisfactory experiments, that a fluid of this kind is actually disengaged by firing the powder; and that it ispermanentlyelastic, or retains its elasticity when cold, the force of which he measured in this state. He also measured the force of it when inflamed, by a most ingenious method, and found its strength in that state to be about a thousand times the strength or elasticity of common atmospheric air. This, our Doctor observes, is not its utmost degree of strength, as it is found to increase in its force when fired in larger quantities than those employed by Mr. Robins; so much so indeed, that by more accurate experiments, we have found its force rise as high as 1600 or 1800 times the force of atmospheric air in its usual state. Much beyond this it is not probable it can go, nor indeed possible, if there be any truth in the common and allowed physical principles of mechanics. With an elastic fluid, of a given force, we infallibly know, or compute the effects it can produce, in impelling a given body; and on the other hand, from the effects or velocities with which given bodies are impelled by an elastic fluid, we certainly know the force or strength of that fluid, and these effects we have found perfectly to accordwith the force above mentioned. Mr. Robins’s discovery and opinions have also been corroborated by others, among the best chemists and philosophers. Lavoisier was of opinion that the force of fired gunpowder depends, in a great measure, on the expansive force of uncombined caloric, supposed to be let loose in a great abundance, during the combustion or deflagration of the powder. And Bouillon Lagrange, in his course of Chemistry says, when gunpowder takes fire there is a disengagement of azotic gas, which expands in an astonishing manner when set at liberty; and we are even still ignorant of the extent of the dilatation occasioned by the heat arising from the combustion. A decomposition of water also takes place, and hydrogen gas is disengaged with elasticity; and by this decomposition of water there is formed carbonic acid gas, and even sulphurated hydrogen gas, which is the cause of the hepatic smell emitted by burnt powder.
It has been found by experiment, that granulated powder inflames with much greater rapidity than that which is not granulated; the latter only puffs away slowly, while the other takes fire almost instantaneously; and of the granulated kinds, that in round grains much sooner than that in oblong irregular grains; the cause of which may arise from the former leaving to the flame larger and freerinterstices, which produce the inflammation with much more rapidity.
Gunpowder is supposed to explode at about 600° Fahr. but if heated to a degree just below that of faint redness, the sulphur will mostly burn off, leaving the nitre and charcoal unaltered.
Experiments have also proved, that the variations in the state of the atmosphere do not any way alter the action of powder. By comparing several trials made at noon in the hottest summer sun, with those made in the morning and evening, no certain difference could be perceived; and it was the same with those made in the night, and in winter. And indeed, considering the principles of the explosion, and that it always contains the same quantity of the elastic fluid, it is difficult to conceive how its force can be affected by the density or rarity of the atmosphere.
The action and nature of this formidable composition being now somewhat fully described, we shall proceed to the principal object of our Work, that of constructing the most common and curious articles for Pyrotechnic exhibitions.