Camphor is employed in those fire-works chiefly, which are exhibited in rooms; its expense being an objection to its use in large exhibitions. In what are termed perfumed pastes, or mixtures, scented fire, or odoriferous fire-works, it is used in abundance: in fact, it enters into nearly all the compositions of this kind. Camphor, besides producing, alone, a white flame, gives a brilliant light, and, when mixed with other substances, adds greatly to the appearance of the flame; and, giving out a powerful odour, destroys, in a measure, the disagreeable smell arising from the combustion of the sulphur and nitre.

By referring to the article on Greek fire, and some incendiary preparations used in war, it will be seen, that camphor is an important constituent. As camphor is very combustible, and will even burn on the surface of water, it is well adapted for all those purposes. We have already spoken of the Greek fire; and it seems, that the peculiar character of that fire, of burning in water, was owing to the presence of camphor. This opinion appears plausible, when we consider, that some preparations have been made with camphor, which had the property of burning on water.

Camphor may be pulverized by the assistance of, and brought into intimate mixture with, nitre and sulphur; because the former, in particular, tends to divide it. But it may be pulverized separately, and afterwards added to the composition, by rubbing it in a mortar with a small quantity of alcohol, or spirit of wine; or, if this cannot be had, with fourth proof brandy. As camphor is very inflammable, its effects, when mixed with saltpetre and fired, are much the same as those produced by other resins, or concrete oils. A combustion, more or less rapid, ensues, and, while the nitre itself is decomposed, the camphor also undergoes the same change, producing both water and carbonic acid, from the union of two of its elements, the hydrogen and carbon, with the oxygen of the nitric acid. In all cases, in which camphor is employed in artificial fire-works, although its own flame is white, it may assist in increasing the flame, which, however, is modified, according to the substances, which enter into the composition. These may not retard its combustion, but, nevertheless, may change the appearance of the flame; as is the case, when we employ the filings of iron, steel, brass, or zinc, sal ammoniac, rosin, saw-dust, and other substances, which usually form a part of such mixtures. Upon the whole, then, we may consider, that camphor acts in fire-works; 1st, as an inflammable body; 2ndly, that, besides being in a great measure decomposed, a portion of it is evaporated, and communicates, to the surrounding atmosphere, a peculiar smell, which is recognised in the odoriferous fire-works; 3rdly, that, while it acts in taking a part of the oxygen from the nitric acid of the nitre, it assists in the decomposition of this salt, more especially if it be mixed separately with the nitre; 4thly, that, in all instances of its combustion, while it acts primarily on the nitre, with the oxygen of which it forms both water and carbonic acid, it, at the same time, increases the flame, which may be either white, red, or yellow, according to the other substances employed; and, finally, it may be thrown out in the state of combustion, and receive, for the further support of its combustion, the oxygen of the air, and hence produce a white exterior flame, while that in the immediate vicinity of the composition may be more or less coloured. But its application, the proportions in which it is used, as well as the kind of fire-works to which it is applicable, will be considered at large in other parts of the work.

The great inflammability of camphor is to be ascribed to its containing a large quantity of carbon and hydrogen, and a small quantity of oxygen.

There is a preparation, called artificial camphor, that is formed by passing muriatic acid gas through spirit of turpentine. It inflames with facility, and burns, without leaving any residue. Might not this preparation be economically employed, in lieu of camphor, for incendiary fire-works?

Sect. XVI. Of Gum Benzoin, and Benzoic acid.

Gum Benzoin, or Benjamin, is considered a solid balsam, and is the production of a tree, which grows in Sumatra, &c. called the styrax benzoe. It is obtained from this tree by incision, a tree yielding three or four pounds. It is a brittle substance, sometimes in the form of yellowish-white tears and called, from that circumstance, almond benzoin. Besides a resinous substance, it contains an acid, called the benzoic or flowers of benzoin, a substance similar to balsam of Peru, being a peculiar aromatic principle, soluble in alcohol and water. By heating it, or by combustion, it evolves a very agreeable smell, and is, therefore, used in those fire-works which are exhibited in rooms, theatres, &c. and also in the composition of odoriferous fire-works. Besides being in itself inflammable, it produces a peculiar smell, arising, in all probability, from an essential oil, aided, in some degree, by the separation of benzoic acid.

It has been examined by Bucholz and Brande. Its general properties are: that it is insoluble in water, although hot water takes up a part of it, said to be the benzoic acid. It is soluble in alcohol, from which it is separated by muriatic and acetic acids, but not by the alkalies. It is also soluble in ether.

The benzoic acid, or flowers of benzoin, are obtained from it by sublimation. A quantity of the powdered gum, put into an earthen basin, a thick paper cone being tied round the rim, and heat applied, the acid will leave the resin, and be condensed on the inner side of the cone. Bucholz (Bulletin de Pharmacie, v. p. 177) has given a process for obtaining it by means of alcohol, and some others have been adopted. By boiling four ounces of the gum in powder in a sufficient quantity of water, with three drachms of carbonate of soda, the acid will unite with the alkali, and form a benzoate of soda, which, when filtered and decomposed by sulphuric acid, will yield the benzoic acid. Five drachms of acid will be thus obtained. Lime has been used in the same manner as soda, and the acid separated by the addition of muriatic acid.

Flowers of benzoin may be used in the place of the gum; using, however, but a small quantity. They will communicate the same odour to fire as the benzoin. The flowers, or acid of benzoin, are so inflammable, as to burn, with a clear yellow flame, without the assistance of a wick. It is soluble in ardent spirits, in oils, and in melted tallow. The compounds, which it forms with them, are also inflammable. Benzoic acid is considered to be an oily acid, and contains, no doubt, a very large proportion of hydrogen.

Sect. XVII. Of Storax Calamite.

Storax is the most fragrant of all the balsams. It is afforded by the styrax officinalis, a tree which grows in the Levant. It is sometimes in red tears. Common storax is in large cakes, and brittle and soft to the touch. This is more fragrant than the other sort, but is frequently adulterated with saw-dust. It is soluble in alcohol, and is said to yield some benzoic acid.

Styrax is a different substance; a semi-liquid juice obtained from the liquidambar styraciflua. Its odour is less agreeable than that of storax calamite. It is used in odoriferous fire, in pastes, in the composition for scented vases, and the like.

Sect. XVIII. Of Essential Oils.

Essential or volatile oils, as well as the raspings of red cedar, dried rosemary, and other fragrant plants, are all used in the preparation of odoriferous fire. In some preparations, the oil of roses is employed; in others, the essence of bergamot, of lemon, &c. which, being very volatile, evaporate in a moderate heat, and, being also inflammable, may assist in the combustion. In the case of the raspings of cedar in particular, it also communicates a peculiar appearance to the flame.

Oils, whether essential or fixed, when passed through ignited tubes, are decomposed, and furnish an inflammable gas called olefiant gas. Wax, tallow, &c. produce the same gas, the hydroguret of carbon. Messrs. Taylor and Martineau contrived an ingenious apparatus for generating gas from oil on the great scale, as a substitute for candles, lamps, and coal gas, it being much preferable for burning, as it contains no sulphur, and does not injure furniture, books, plate, paint, &c. Oil gas contains more hydroguret of carbon than coal gas, which is a great advantage, enabling one cubic foot of oil gas to go as far as four of coal gas. An elegant apparatus was erected by Taylor and Martineau at the Apothecaries' Hall, London, a drawing of which may be seen in the 15th number of the "Journal of Science and the Arts."

It is to be observed, that odoriferous fire-works are intended for exhibition in close apartments; so that the smell of certain gases, produced by the nitre, charcoal, and sulphur, according to the preparation used, will be more or less destroyed. Such preparations are, nevertheless, expensive, and for that reason seldom used.

Sect. XIX. Of Mastich.

This resin, obtained, from the pistacia lentiscus, by making transverse incisions in the tree, is first in a fluid state, and gradually concretes into yellowish semi-transparent brittle grains. In Turkey, great quantities of it are used for sweetening the breath, and strengthening the gums. It is from the use of the resin as a masticatory, that its name is said to be derived. It is not completely soluble in alcohol, a soft elastic substance separating from the solution. When exposed to heat, it melts, and exhales a fragrant odour: for which reason, principally, it enters into the composition of some fire-works, as the scented paste. In ordinary fumigations, mastich is commonly used.

Sect. XX. Of Copal.

Gum copal, by which name it is known, is a resin, obtained from a tree, called thus copallinum. It is often in the form of a beautiful white resin; but sometimes it is more or less coloured. It is frequently opaque. It may be dissolved in alcohol, spirit of turpentine, and oils, by a peculiar management, (by using camphor, previously melting it, and the like,) and then it forms the various copal varnishes, which are more or less perfect, as the copal is transparent, and the solution properly formed. When heated, it melts like other resins, and in this, and many other properties, it partakes of the character of resins in general. It is used in some of the formulæ for fire-works.

Sect. XXI. Of Myrrh.

Myrrh is obtained from a plant, supposed to belong to the genus mimosa, which, as Bruce informs us, (Travels, &c.) grows in Abyssinia and Arabia. It is in the form of tears, of a reddish-yellow colour; sometimes transparent, and at other times opaque. It possesses a peculiar odour, and a bitter and aromatic taste. It burns with difficulty, and does not melt when heated. With water, it forms a yellow opaque mixture. It dissolves in alcohol, and the solution is decomposed by the addition of water, the whole becoming opaque. According to Braconnot, myrrh is composed of 23 resin, and 77 gum, in the 100 parts. Pelletier, whose analysis differs from Braconnot's, observes, that, besides resin, it contains some volatile oil, to which, no doubt, its fragrance is owing. The gum, extracted from it, had the character common to all gums, with the exception, that, instead of forming the mucous or saclactic acid, by the action of nitric acid, it produced only oxalic acid.

That myrrh burns with difficulty, is owing entirely to the presence of so much gum, and, comparatively speaking, the small quantity of resin, which enters into its composition. But, notwithstanding this property, as it partakes of a fragrant oil, it is used in some compositions for fire-works. The gummy part may retard, as is sometimes required in particular preparations, the rapidity of the combustion, and therefore have a two-fold effect when employed in fire-works.

Sect. XXII. Of Sugar.

Refined sugar is sometimes used in pyrotechno-mixtures. As it is a vegetable oxide, (composed of carbon, hydrogen, and oxygen), which is decomposed by heat, and has the property of decomposing nitric acid, and some of its combinations; its operation in such mixtures may be readily perceived. We have seen, when treating of chlorate of potassa, that, when this salt and sugar are mixed together, and sulphuric acid poured on the mixture, a rapid combustion ensues, which is owing as well to the decomposition of the sugar, as to that of the salt. The matches, likewise, which inflame by immersion in sulphuric acid, are covered with a similar mixture. That sugar, therefore, has the property of decomposing those salts, which are composed of acids, that have their oxygen but feebly combined, and thereby producing combustion, according to the temperature employed, or other agents made use of, is evident from a variety of experiments. By its action, then, in such cases, the products of combustion, arising from the elementary parts of the sugar alone, uniting with oxygen, must be carbonic acid and water. Sugar, submitted to destructive distillation, affords a variety of new substances; among which we may notice caromel, or that peculiar odour, which is recognised in the burning of sugar. Sugar may, therefore, besides assisting in part in the decomposition of saline bodies, and particularly nitre, and perhaps giving rise to new products, with which we are unacquainted, have another effect, that of destroying the offensive smell of other substances, by means of the caromel formed. Sugar, also, when mixed with various bodies, and struck with a hammer, will produce detonations.

Sugar, when used in compositions of fire, should be pure; and it may be known to be so, by producing invariably a phosphorescence in the dark, when two pieces are rubbed together. At a red heat, it bursts into flame with a kind of explosion. This flame is white, with blue edges.

Sugar is obtained from the sugar-cane; from the sap of the sugar-maple; from beets and grapes; and from various other saccharine bodies. It is formed also artificially, by the action of sulphuric acid on starch.

Mr. Kirchoff, a Russian chemist, accidentally discovered that starch may be changed into sugar by diluted sulphuric acid. One hundred parts of starch yield one hundred and ten of sugar. It appears, that, by the abstraction of a little hydrogen and carbon, starch will be converted into sugar. Potatoes, digested with diluted sulphuric acid, Dr. Ure found, would also form sugar, and very abundantly. The sulphuric acid may be removed by the addition of chalk, and, as the sulphate of lime is but slightly soluble, the pure saccharine fluid may be obtained by filtration. The sugar is procured in a solid state by evaporation, and may be clarified like other sugar. Dr. Ure observes, that good beer has been made from starch-sugar, but recommends potato-sugar. To obtain the latter, the potatoes are washed, grated down, and treated with the dilute acid for a day or two, at a temperature of 212°.

The observations of Braconnot are interesting. He has succeeded in converting a variety of vegetable substances into gum and sugar. The conversion of wood into sugar, however remarkable it may seem, has been effected; and a pound weight of rags will, by the same process, make more than a pound weight of sugar. Rice, as it contains a large quantity of fecula, may, we have no doubt, be converted, in the same manner, into saccharine matter.

When sugar is first obtained, it is impure, containing a variety of foreign substances, and more or less brown, as the Muscovado of the West India islands. It is refined, and formed into loaves, by treating its solution in water with bullocks' blood, the serum of which coagulates by heat; and, finally, by pouring the sugar, when sufficiently boiled, into conical earthen moulds, where it concretes. It is clayed, by putting a mixture of white clay and water on the sugar in each of the cones; the water from which passes through, and renders it beautifully white. The same process may be repeated; hence the single and double refined sugar. The molasses passes out from the sugar at the apex of the cone, and is received in vessels.

From twenty to thirty-five per cent. of molasses are separated in the refining of raw sugars; and it is supposed, that a considerable part of it, probably two-thirds, are formed by the high heat used in the concentration of the sirup. In order to prevent so great a quantity of molasses, different plans have been recommended. That of Howard is highly spoken of. It consists in surrounding the sugar-boiler with oil or steam at a high temperature, instead of exposing it, as heretofore, or the mode usually adopted, to the naked fire. The boiler is covered at top, and, by means of an air-pump, the air is exhausted, and the pressure of the atmosphere being removed, ebullition takes place at a lower temperature. No blood is used in Mr. H.'s process, instead of which, the clarification is performed by means of canvass filters, adding previously a pasty mixture of gypsum and alumina, made by saturating a solution of alum with quicklime. He does not employ clay, as is done in whitening the sugar; but, in its place, makes use of very pure saturated sirup. He uses animal charcoal, (bone black), which has the property of destroying vegetable colouring matter. Wilson's process for refining sugar possesses some advantages. It will be found in the 34th volume of the Repertory of Arts. The patent filtering apparatus of Sutherland is highly approved.

The chemical properties of sugar are the following: It is very soluble in water, both hot and cold; it forms with water a sirup, which on standing will crystallize, forming the candied sugar. It is not acted upon by oxygen gas. It is capable of combining with, and, according to some chemists, of neutralizing acids and alkalies. It is decomposed by nitric acid with effervescence, being converted into oxalic and malic acids. Tartaric, acetic, and oxalic acids prevent it from crystallizing. It unites with lime and strontian, but is partially decomposed by barytes. It combines also with oxide of lead, which it precipitates from its solution, forming, as it is called, a saccharate of lead. Alcohol has some action on it, and also hydrosulphurets, sulphurets, and phosphurets of alkalies and alkaline earths. On the application of heat, it melts, swells, becomes brownish-black, and exhales a peculiar odour, which we have mentioned, and, at a red heat, takes fire. Lastly, though possessed of some general and specific characters, it differs, in some of its properties, according to the substance from which it is obtained.

Sect. XXIII. Of Sal Prunelle.

This salt is nothing more than nitrate of potassa, melted in a crucible, and poured into moulds, whence it receives the form under which it is found in the shops. The saltpetre, when merely fused, is not decomposed, as it is when exposed to a red heat in an iron retort. In the former case, the water only which it contains is separated; but, in the latter, the salt itself is decomposed, and oxygen gas evolved. Sal prunelle, therefore, is fused saltpetre. Combustible bodies, as charcoal, sulphur, phosphorus, oils, resins, &c. have the same effect on it as on ordinary nitre. The only advantage it has over the common refined saltpetre, in the preparation of some fire-works, is, that it is free from water, and more readily acted on by combustible substances. In preparing it, care must be taken in the application of the heat; which, if too powerful, would, besides fusing it, decompose, and convert it into nitrite of potassa. It may be readily pulverized and sifted. For the properties of nitre, see that article.

Sect. XXIV. Of Alcohol.

Alcohol, or rectified spirit of wine, is used for a variety of purposes in pyrotechny, and, when it cannot be procured, strong brandy is substituted. In assisting the pulverization of some substances, as camphor, in forming the mixture of certain pastes, and in acting as a vehicle for the intimate union of some bodies, it is considered a necessary article. Alcohol may be made to form variously coloured flames, by mixing with it certain saline substances. Thus, boracic acid will form a green flame; muriate of strontian, a carmine red; muriate of lime, an orange; nitrate of copper, an emerald green; nitre, common salt, and corrosive sublimate, a yellow, &c. As alcohol has the property of dissolving essential oils, camphor, &c. it may be used as a menstruum for certain oils in the preparation of odoriferous fire-works. See Articles on coloured flame, and odoriferous fire.

Alcohol constitutes a part of all ardent spirits, wine, cider, beer, &c. in which it is combined with water, or with water and mucilaginous and colouring matter. It is formed in the vinous fermentation, and always results from the union of carbon and hydrogen. During the process, carbonic acid gas is liberated. Fermented liquors, therefore, or those which have passed through the vinous fermentation, always contain alcohol in more or less abundance, but mixed with water in many instances. In some it is accompanied with water, and saccharine, mucilaginous, and extractive matter. The different kinds of beer is an example of this fact. When liquors, which contain spirit, are submitted to distillation, the product is alcohol and water; for the volatile parts evaporate, and the fixed substances remain in the still. The spirit partakes, more or less, of a peculiar taste and flavour, by which liquors are distinguished from each other. On this subject, however, it will be sufficient to add, that brandy is procured by the distillation of wine; rum, from the fermented juice of the sugar-cane; gin, from fermented grain and juniper-berry; whiskey, from the fermented mash of grain, cider, &c. and, generally, the ardent liquors, from pears, peaches, and other substances, by the same process.

Alcohol, therefore, exists in all these distilled liquors, in a greater or smaller quantity, combined with water; and the proportion it bears to the water is known by a standard, as either proof, above proof, or under proof, according as its strength is shown by the hydrometer.

The process of obtaining alcohol in a pure state, (usually called rectified spirit of wine), by which the water is separated from the alcohol, consists in repeated distillations, either alone, or mixed with certain substances, which have the property of uniting with, and keeping down the water, in the act of distillation. These substances are usually potash, and dry muriate of lime, both of which substances have a great affinity for water. The specific gravity of highly concentrated alcohol, at 60° is .820, but that of common alcohol, only .837, at the same temperature.

The properties of alcohol are the following: It is a transparent liquor of an agreeable flavour, and may be changed in this particular, by essential oils. It may be exposed to a low temperature without freezing. It boils at 106°, when of the specific gravity .820, and in a vacuum at 56°. It has a strong affinity for water, with which it combines in any proportion; and the specific gravity varies according to the proportion of the mixture and the temperature, on which are founded the tables of Blagden, Gilpin, and others.

Neither common air, nor oxygen, has any action on alcohol at moderate temperatures, whether in a liquid or aeriform state. On hydrogen, carbon, and charcoal, it has little or no action, but on phosphorus it acts, a portion of which it dissolves. With sulphur, it may be made to unite, as also with the alkalies, but not with the earths, except strontian and barytes. It is decomposed by sulphuric and nitric acids, with both of which it forms ether. It dissolves some salts, and has scarcely any effect upon others. Lastly, it dissolves resins and essential oils; but it neither acts upon gums, properly so called, nor on fixed oils. It is a compound of hydrogen, carbon, and a small proportion of oxygen, and may be decomposed, by passing its vapour through an ignited porcelain tube.

Alcohol, by its combustion, as it is used in spirit-lamps for chemical and other purposes, produces no smoke, in consequence of the carbon it contains being totally converted, during that process, into carbonic acid; and its hydrogen, uniting with another portion of the oxygen of the atmospheric air, passes off in the form of aqueous vapour. Alcohol, used in this way, is preferable to oil; for the latter produces a large quantity of smoke, unless it is burnt in the Argand lamp. Alcohol is inflamed, when it is brought in contact with an ignited body. The combustion is rapid without any residue, and the flame white.

As to the strength of alcohol, the best means of determining it, is with the hydrometer; but usually its proof is ascertained by means of gunpowder. A portion of powder, put into a cup, and alcohol poured on it and inflamed, will, if the latter be strong, be set on fire; if, however, the powder should not take fire, but the flame of the alcohol be extinguished, we infer the existence of water, and that the alcohol is not of the proper strength. This experiment is founded on this circumstance, that, if the alcohol contains water, after the alcoholic portion is all consumed, the water will not only extinguish the flame, but also prevent the inflammation of the powder. The hydrometer, however, is the best experiment, as it determines at once the fact of the strength of the liquor.

Alcohol is used in the preparation of certain fulminating substances, as fulminating mercury and silver in particular; the preparation of which, we will give in the two next sections.

It may not be improper to mention another application of alcohol, that of forming the aphlogistic lamp, or lamp that burns without flame. The following description of it, is given by Accum, in his Chemical Amusements, Am. Ed. p. 355. "In a common lamp, with a wick of about half a dozen common threads of cotton wick, used for lamps, put some good spirit of wine. Dispose the threads of wick, not intertwined, but straight and parallel to each other. Take platina wire of the thickness of ¹/₁₀₀th part of an inch; coil it round the wick, about nine coils below, and six coils standing above the top of the wick; the diameter or width of the coils should not be more than ³/₂₀th, or ¹/₇th of an inch wide. Light the wick; and, when the coil of platina above the wick is red-hot, blow out the flame. There will then be a current of pure alcohol, gradually rising from the reservoir below, through the wick, sufficient to keep the upper coil of platina red-hot, until the whole of the alcohol is consumed. This lamp has kept constantly lighted during sixty hours. By means of it, a match, a bit of spunk, or candle may be lighted when wanted. The quantity of alcohol consumed is not much: about an ounce, or an ounce and a half during the night, from bed-time until morning will suffice." This article was added to Accum by Dr. Cooper. A figure of the lamp is in Brande's Chemistry. Dr. Comstock has a paper on the aphlogistic or flameless lamp, in Vol. IV. p. 328, of Silliman's Journal of Science and Arts, which contains some judicious and useful remarks. Sir H. Davy (Journal of the Royal Institution) has discovered, that the vapour of camphor answers the same purpose as alcohol. If a platinum wire be heated and laid upon camphor, it will continue to glow as long as any remains, and the wire will frequently light it up into flame. Davy found, that, in the slow combustion of alcohol, &c. an acid was generated, to which he gave the name of Lampic acid. Faraday and Daniel (Journal of Science and the Arts) have confirmed his conclusions.

Dr. Marcet has proposed a method of producing an intense heat, by causing a current of oxygen gas to pass through the flame of alcohol. The construction of the lamp and gas-holder may be found in the Archives des Découvertes, Vol. vii, p. 61.

Sect. XXV. Of Fulminating Mercury.

Howard's fulminating mercury is less dangerous than either fulminating silver, or fulminating gold. The extreme force of detonation which it possesses is remarkable. The temperature required for its explosion is 360 degrees. Friction, percussion, electricity, and the flint and steel will produce this effect. It gives rise to a stunning disagreeable report, and its force is sufficient to indent both the hammer and the anvil. Four or six grains are sufficient for an experiment. It is rather singular, as Mr. Cruikshank first observed, that this powder will not inflame gunpowder; as may be shown by spreading some of the former on paper, and shaking gunpowder over it, and then firing the mercurial powder. The grains of the gunpowder may be collected entire after the explosion.

From the experiments of Howard, it appears, that this powder is composed of oxalate of mercury, and nitrous etherised gas. Fourcroy, however, has shown, that it varies in its nature, according to the mode of its preparation.

There is also a preparation of mercury, which is likewise explosive, discovered by Fourcroy. This compound may be formed by digesting the red oxide of mercury in liquid ammonia for the space of eight or ten days. The oxide assumes a white colour, and at last appears in crystalline scales. Upon ignited coals, it detonates loudly like fulminating gold, which see below. In a few days, however, it loses its fulminating property, and undergoes spontaneous decomposition. Exposed to a low heat, the ammonia is disengaged, and an oxide of mercury remains.

As ammonia forms several detonating compounds with metallic oxides, the theory of their explosive effects is the same; viz. that, while the hydrogen of the ammonia unites with the oxygen of the oxide, forming water, the azote is disengaged in the state of gas.

The process for preparing Howard's fulminating mercury is the following, dissolve one hundred grains of mercury in an ounce and a half (by measure) of common nitric acid, assisting the solution by heat. When cold, pour the solution upon two ounces (by measure) of strong alcohol, and apply a moderate heat, until the mixture begins to effervesce. A white fume then begins to undulate on the surface of the liquor, and a white powder precipitates, which is the fulminating mercury. This powder is to be immediately washed with cold water, and dried at a heat, not much exceeding that of boiling water. One hundred grains of mercury, will give, on an average, one hundred and twenty-five grains of the powder.

The products of its combustion are carbonic acid gas, azotic gas, water, and mercury. Besides by percussion, it is inflammable when brought in contact with sulphuric acid. It is supposed, that fulminating mercury sometimes contains ammonia, and that the products of combustion, according to the mode of preparation, are therefore different. The reader may consult some interesting observations on this powder in the Journal de l'Ecole Polytechnique.

M. Bayen, an apothecary, in 1779, (Journal de Physique), announced a process for preparing fulminating mercury. His process, however, is different from that described. A solution of mercury is made in nitric acid, and precipitated by caustic alkali. The precipitate (oxide of mercury) is then caught on a filter, washed, and dried. Thirty grains of this powder, mixed with four or five grains of sulphur, and struck with a heavy hammer, or heated on an iron, will explode with violence. The oxide of mercury, obtained from its solution by lime-water, has the same effect, when treated in the same manner. Another process recommended is, to precipitate a solution of the perchloride of mercury (corrosive sublimate) by lime-water, and treat the precipitate with sulphur, as above described.

Sect. XXVI. Of Fulminating Silver.

This compound, which is more powerful than fulminating mercury, is prepared also with alcohol. Descostils (Annales de Chimie, LXII. p. 198,) Cruikshank, and Brugnatelli, have all written upon it.

Fulminating silver explodes without much heat. By the slightest friction it is inflamed, and detonation follows. Hence it is used in the form of toys, in fulminating balls, bombs, crackers, &c. which explode by falling on the ground. Torpedoes, pulling crackers, &c. are formed of this powder. The fulminating balls are made of glass, and contain a grain or two of fulminating silver, mixed with sand. The same mixture, put on the ends of two strips of paper, and the ends pasted, forms the pulling crackers; for the moment they are pulled asunder, the friction produced sets the fulminating silver on fire, and causes a detonation.

The same preparation placed on a wafer, and the wafer put between paper, as in the sealing of a letter, will explode, when the paper or the wafer is broken. Fulminating bombs are balls of the size of a hazle nut, containing about three grains of the fulminating silver. Their explosive effects are said to be violent. See Detonating Works.

This powder, in consequence of its powerful action, is dangerous; and, as it explodes so readily, it should never be put into a phial, nor should it be touched or handled in any way that can produce friction. Even when made to approach the flame of a candle, it will explode with extreme violence.

The preparation of Brugnatelli's fulminating silver consists in reducing 100 grains of nitrate of silver (lunar caustic) to powder; and, when put into a basin, pouring over it one ounce of alcohol, and the same quantity of nitric acid. The mixture will become hot, effervescence will ensue, while the whole will assume an opaque or milky appearance.

When the gray powder of the nitrate has become white, and the mixture acquires consistency, distilled water is to be added, to suspend the action. The white precipitate is then to be washed by repeated affusions of cold water, and dried in the open air, but in a dark place, so as to seclude it from the light.

In fact, this process is similar to that for preparing fulminating mercury; for it is nothing more than treating silver with nitric acid and alcohol. Cruikshank employs forty parts of silver, sixty parts of nitric acid, and sixty parts of alcohol, from which sixty parts of the powder are obtained.

Berthollet considers this powder to be composed of ammonia, and oxide of silver, and the theory of its detonation to be the same as that of fulminating gold. In its explosion, the oxygen of the oxide of silver unites with the hydrogen of the ammonia, and the nitrogen is disengaged.

Berthollet's fulminating silver, which he discovered in 1788, is another preparation, which fulminates powerfully. It is prepared by precipitating nitrate of silver by lime-water. The precipitate is placed on filtering paper, which absorbs the water, and the nitrate of lime. Pure caustic ammonia is then added, which produces an effect somewhat similar to that attending the slaking of lime. The ammonia dissolves only a part of this precipitate. It is left at rest for ten or twelve hours, and at the expiration of this time, there is formed, on the surface, a shining pellicle, which is re-dissolved with a new portion of ammonia, but which does not appear, if a sufficient quantity of ammonia has been added at the first. The liquid is then separated, and the black precipitate, found at the bottom, is put, in small quantities, on separate papers. This powder explodes even when moist, if struck with a hard body. When dry, the slightest friction will explode it. Its detonation is owing to the same cause as that producing the explosion of the other preparation of this metal, as it is also composed of oxide of silver and ammonia.

The fulminating silver of Chenevix explodes only by a slight friction in contact with combustible substances. It is nothing more than chlorate of silver. It is formed by passing chlorine gas through alumina, diffused in water, and afterwards digesting, in the liquor, some phosphate of silver. The whole is to be evaporated slowly. A single grain of this powder, with three grains of sulphur, will explode by the slightest friction.

For the preparation of fulminating silver, the formula given by professor Silliman of Yale College, appears to possess some advantages. To an ounce of alcohol and as much nitric acid, he adds 100 grains of pulverized lunar caustic. A gentle heat is applied to excite the action between them, which must be removed, the moment they begin to act. When a thick white precipitate appears, cold water must be added to check the action. The precipitate is then to be collected, washed, and carefully dried. A grain or two will explode over a candle.

Sect. XXVII. Of Fulminating Gold.

The preparation, called by some aurate of ammonia, is formed by dissolving gold in nitromuriatic acid, diluting the solution with water, and adding gradually liquid ammonia, until the precipitation ceases. The precipitate is then to be caught on a filter, well washed with water, and dried in the air. The fulminating gold, thus produced, exceeds the weight of the original gold employed by thirty-three per cent.

Three or four grains of this powder, heated on a knife, will explode with a loud report. The temperature required for its explosion is between 230° and 300°. Ten or twelve grains will penetrate a copper-plate, of the thickness of a playing card. The facility with which this powder explodes, is increased by drying. If it be heated until it becomes black, the slightest touch will cause a detonation. This powder is composed of oxide of gold, ammonia, and a portion of chlorine; and, during its detonation, water, nitrogen and chlorine are evolved, the gold being revived.

The presence of ammonia is necessary to give to gold the property of fulminating. Fulminating gold accordingly loses this property, the moment the ammonia is separated. Concentrated sulphuric acid, melted sulphur, fat oils, and ether have this effect.

The discoverer of fulminating gold was a German Benedictine Monk, who lived about the year 1413. Basil Valentine has described the preparation of it very accurately. He recommends, however, mixing sal ammoniac with aqua fortis, the old mode of making aqua regia, and distilling the mixture; then putting in the gold in leaf. After the acid is saturated, he adds oleum tartari, or sal tartari (carbonate of potassa) dissolved in water; and the precipitated calx, thus obtained, when collected, washed, and dried in the open air, will fulminate. In this process, it is evident, that the aqua regia, prepared with sal ammoniac, contains ammonia, and, when the gold is dissolved, and the potash added, the oxide of gold separates, and, from the composition of the powder, must combine with a portion of ammonia, and hence produce fulminating gold. He remarks, that distilled vinegar digested on fulminating gold, destroys its fulminating properties, and observes also, that care must be taken to prevent its explosion. He also knew that sulphur would have the same effect.

Bergman (Treatise on Pulvis Fulminans) describes the process employed by Valentine; and Beckman (History of Inventions, v. iii. p. 132,) observes, that, after the time of Valentine, Crollius, who lived in the last half of the 16th century, was well acquainted with fulminating gold, and made its preparation more generally known. In the Oswaldi Crollii Basilica Chymica, 4to, p. 211, published at Frankfort, in 1609, the process is also to be found. He calls it aurum volatile, and speaks of its being useful in medicine. Beguin, however, appears to have given it the appellation of aurum fulminans, if we judge from his Tyrocinium Chymicum, 12mo, printed in 1608.

Sect. XXVIII. Of Fulminating Platinum.

While noticing explosive compounds, it may not be improper to mention that of platinum, lately discovered by Mr. E. Davy. It explodes, when heated to 400 degrees, with a sharp report, similar to that produced by fulminating gold; but neither friction nor percussion will decompose it. It is formed by making a solution of platinum in nitromuriatic acid, and passing through it, sulphuretted hydrogen gas, until no further precipitation ensues. This precipitate, when collected, and digested in nitric acid, is converted into sulphate of platinum. This is dissolved in water, and liquid ammonia then added. The precipitate, now formed, is washed, and boiled in a solution of potassa, and, after having freed it from the adhering potassa, is suffered to dry. All fulminating ammoniacal compounds are analogous; and fulminating platinum, being composed of oxide of platinum, ammonia, and water, is decomposed in the same manner as these compounds.

Fulminating platinum is composed as follows:

Sect. XXIX. Of Detonating Powder from Indigo.

Iodine is a particular substance, which has the property not only of combining with oxygen and hydrogen, forming iodic and hydriodic acid, but also with various bases constituting a class of bodies, called iodides. Its union with azote produces a singular substance, which detonates with great violence, when slightly touched or heated. It may be formed, by putting a quantity of iodine into the water of ammonia. It will be gradually converted into a brownish-black matter, which is the iodide of azote. It is formed in this process by the iodine, in the first instance, decomposing a part of the ammonia; the hydrogen of which combines with a portion of the iodine, and produces hydriodic acid, which then unites with the undecomposed part of the ammonia, and forms the hydriodate of ammonia; whilst the azote the other constituent of the ammonia, unites with another portion of the iodine, and forms the compound in question.

When exposed to the air, iodide of azote gradually flies off in vapour, without leaving any residue. The products of its detonation are iodine and azotic gas.

The iodide of azote was discovered by M. Courtois, and subsequently examined by M. Colin. Iodine, brought in contact with ammoniacal gas, a combination taking place, produces a viscid shining liquid of a brownish-black colour, which, as the saturation goes on, loses its lustre.

This liquid does not detonate, and is considered to be an iodide of ammonia; but, when it is added to water, it is decomposed, as well as the water, and we obtain two new compounds, as before observed, the hydriodate of ammonia, and iodide of azote. This iodide detonates. Hence it is evident, that hydrogen united with azote, in ammonia, prevents explosion; for the moment it is taken away, by the formation of hydriodic acid, and the azote itself combines with the iodine, a fulminating compound is formed. The elements of this powder are feebly united.

It is found, that hydriodate of ammonia has the property of dissolving a large quantity of iodine, and, if suffered to remain with the iodide of azote, of decomposing it also, and setting the azote at liberty. Water is said to have the same effect, although feebly.

Iodate of potassa, a salt composed of iodic acid and potassa, when mixed with sulphur, and struck with a hammer, will detonate, in consequence of the decomposition of the iodic acid. The iodate of potassa may be formed very readily by agitating iodine with a solution of caustic potassa. The water is decomposed, and the hydriodate of potassa is also formed, which, being very soluble, remains in solution, whilst the iodate separates, on concentrating the liquor, and suffering it to stand.

Chlorate, as well as nitrate of silver, form with sulphur fulminating powders.

Iodic acid, called also oxy-iodine, (prepared by exposing iodine to the action of euchlorine,) when heated in contact with inflammable substances, and the more combustible metals, will produce detonations.

It appears, however, that sulphur has a stronger affinity for oxygen than iodine has, and iodine a stronger affinity than chlorine for the same element. Hence chloric acid is more readily decomposed by inflammable bodies than iodic acid, and iodic acid, sooner than sulphuric acid.

The acids, which chlorine, iodine, and sulphur form respectively with oxygen, Gay-Lussac remarks, have their elements more strongly condensed, than the same substances united with hydrogen.

Sect. XXXI. Of Detonating Oil, or Chloride of Azote.

In vacuo, it expands into vapour, which still possesses the power of exploding by heat. In water, it gradually disappears, the water becoming acid, and azote being evolved. Mercury decomposes it, and a white powder (calomel) is formed, while the azote is set at liberty.

Dr. Ure (Chemical Dictionary, Art. Nitrogen,) observes, that the mechanical force of this compound, seems superior to that of any other known substance, not even excepting the ammoniacal fulminating silver. The velocity of its action appears to be likewise greater.

The Doctor touched a minute globule of it, in a platina spoon, resting on a table, with a fragment of phosphorus at the point of a pen-knife, and the blade was instantly shivered into fragments by the explosion.

Messrs. Porret, Wilson, and Kirk (Nicholson's Journal, Vol. XXXIV,) employed 125 different substances, by bringing them in contact; and out of that number the following caused it to explode: