Chapter II (9)

Linseed oil unites with great ease with oils, tallow, fat, wax, &c. Some of these compositions are used in fire-works. A preparation of pitch, mutton suet, and linseed oil is used, for instance, in preventing the access of moisture to fuses; and in military fire-works, it is employed in combination with pitch, rosin, mutton suet and turpentine for incendiary works. Wax, and tallow, we may here add, are also used in the preparations of similar works.

_Sec. LI. Of Gum arabic, and Gum Tragacanth._

Gum arabic, which exudes from a tree that grows in Egypt and Arabia (_Mimosa nilotica_) when pure is transparent, and nearly colourless. There are several varieties of this gum; the _gum senegal_, for instance, which is of a reddish colour, and occurs in larger pieces. Other mucilaginous substances, the peach tree gum, the cherry tree gum, &c. which exist only in small quantities, are analogous to the gum of the Mimosa.

Gum arabic is brittle, and for that reason may be easily reduced to powder. It is readily dissolved in water, with which it forms mucilage. In this state, it is employed in fire-works, chiefly as a vehicle for the mixing of pastes, matches, &c.

Gum is a vegetable oxide, composed of carbon, hydrogen, and oxygen. It does not crystallize. It is precipitated by some metallic salts, as acetate of lead. It is insoluble in alcohol, which distinguishes it from resins. Nitric acid decomposes it, and changes it into the saclactic or mucous acid. With sugar, the same acid produces oxalic acid.

Gum tragacanth, or gum dragon, is the produce of a thorny shrub, which grows in Candia, and other islands of the Levant, called _astragalus tragacantha_. The gum obtained from this shrub has many properties in common with gum arabic, and is, therefore, used as a paste. It dissolves readily in boiling water; but is insoluble in alcohol, or ether.

It consists, almost entirely, of a peculiar vegetable principle, which is called _cerasin_ by Dr. John. Cerasin has the adhesive qualities of gum arabic, but in a greater degree. It is said to constitute a part of the gummy matter, that exudes from the _prunus cerasus_, _prunus avies_, _prunus domestica_, &c.

_Sec. LII. Of Cotton._

The soft down, which envelopes the seeds of different species of _gossypium_, or cotton plant, is the cotton of commerce. These plants are natives of warm climates. Cotton when bleached is perfectly white. It is extremely combustible, and burns with a clear lively flame. The ashes left behind contain potash.

Cotton is the substance, usually employed in making match rope, for the communication of fire. It has also other uses in pyrotechny. Cotton match is much used in fire-works for exhibition, not only for single cases, but also for a series of cases of artificial fire, either for fixed or moveable pieces; and serves to communicate fire, either singly, or from one case to another, or to the whole piece at one time. Matches, so used, are called leaders, and are generally confined in paper tubes.

Cotton is one of the best applications to recent burns. Applied to the part, it will, in a surprising manner, abate the violence of the pain, and remove the inflammation.

Cotton is soluble in alkaline ley. For some of the earths, it has a strong affinity, particularly alumina; as also for several metallic oxides, and tannin. The action of mordants, in dying of cotton-goods, depends on these affinities. Nitric acid converts it into oxalic acid.

Cotton wick for lamps, candles, &c. is rendered very inflammable by spirit of turpentine. By dipping the end of the wick in turpentine, the candle will inflame at once, the moment flame is applied. For candle-making, the wick is sometimes dipped in a solution of camphor in spirits, or in a melted mixture of camphor and wax. See _Candle_.

_Sec. LIII. Of Bone and Ivory._

Bone, which is considered to be a combination of phosphate of lime, gelatinous matter, animal oil, &c. is used occasionally in fire-works. By destructive distillation, bones, or osseous matter, afford ammonia, Dippel's animal oil, &c.; and, when consumed by fire, leave a white ash, which is composed principally of phosphate of lime. Bone-ash is the result of the combustion of bone; for, while all the gelatinous substance, oil, &c. are burnt off, that, which composes the basis of bone, and which distinguishes it from _gristle_, remains in the form of ash. Bone-ash furnishes phosphorus by a certain process. See _Phosphorus_. Diluted muriatic acid will take up the phosphate of lime of bone and leave the gelatin. This mode is recommended for the separation of gelatin from bone.

Bones, when carbonized in the same manner as wood, furnish what is called _bone-black_, but commonly known by the name of _ivory-black_. It is nothing more than animal charcoal.

In Pyrotechny, bone, in the form of raspings, is employed to communicate a _lustre_ to the flame of gunpowder; but, for this purpose, the most compact, and that, which contains the least gelatin, is usually employed. Hence _ivory_ is preferred. Ivory, in the form of raspings, communicates to flame a bright silver colour; and, on that account, is preferred to all other kinds of bone. The compositions, into which it enters, will be mentioned in a subsequent part of the work.

Ivory is the tusk, or tooth of defence, of the male elephant, and is an intermediate substance between bone and horn, not capable of being softened by fire. The finest and whitest ivory comes from the island of Ceylon. The tooth of the sea-horse is said to approach to ivory, properly so called. It is, however, harder, and, for that reason, preferred by dentists for making artificial teeth. The coal of ivory is remarkably black; but the so called ivory-black, sold in the shops, is nothing else than bone-black.

Bone and ivory may be stained of various colours. One hundred parts of ivory contain,

Gelatin, 24
Phosphate of lime, 64
Carbonate of lime, 0.1

One hundred parts of ox-bone gave

Gelatin, 51
Phosphate of lime, 37.7
Carbonate of lime, 10
Phosphate of magnesia, 1.3

Berzelius, however, detected in bone-fluate of lime, muriate of soda, and uncombined soda. Albumen is most generally present. One hundred parts of bone are reduced by calcination to sixty-three. One hundred parts of human bone afforded Berzelius 81.9 phosphate of lime, 3 fluate of lime, 10 lime, 1.1 phosphate of magnesia, 2 soda, and 2 carbonic acid.

_Sec. LIV. Of Galbanum._

Galbanum is a gum-resin, obtained from the _bubon galbanum_, a plant peculiar to Africa. It is at first a juicy fluid, which exudes when the plant is cut above the root, and hardens by exposure to the air. Alcohol dissolves about three-fifths of it. It contains some volatile oil.

The only instance we know of, in which galbanum has been used in fire-works, is in the composition of rain-fire, employed as an incendiary, before the present _fire-stones_ were invented. The rain-fire, which may be found in the fourth part of this work, it is said, gave rise to the composition of fire-stone. There is no advantage, however, in using galbanum for this purpose; since pitch, tar, turpentine, and many other substances are more inflammable, and, therefore, better adapted for such compositions. We mention it merely because it was one of the ingredients in that once celebrated incendiary preparation, the fire-rain of Siemienowicz.

_Sec. LV. Of Tow and Hemp._

In military fire-works, tow and hemp are much used, and principally for the preparation of incendiary works. Both tow and hemp are employed in forming match. Although old rope, &c. are used for immersion in the tourteaux, carcass, or fire-stone composition, which is readily imbibed, if the rope is untwisted and beaten; yet tow or hemp is a better material, and receives more of the composition. The manner of using it may be seen by referring to the composition for fire-stone. For very nice purposes, the tow or hemp should be well dressed. Flax is, therefore, to be preferred in such cases.

_Sec. LVI. Of Blue Vitriol._

Different preparations of copper are used in fire-works, to communicate colour to the flame; and besides copper filings, brass filings, verdigris, and the oxides of copper, the sulphate of copper, or blue vitriol, has been employed. We may observe here, that there are three sub-species of this salt; the bisulphate, sulphate, and sub-sulphate, the first properly speaking being the blue vitriol of commerce.

The sulphate, although recommended in some of the old formulæ for coloured fire, is not, however, preferable to some other preparations of copper. The use and application of copper, and its preparations, will be seen in the article on coloured fire.

When sulphate of copper is heated, it is converted into a bluish-white powder. If the heat be increased, the acid is expelled, and the black oxide of copper remains. Before it is used, it is exposed to heat to expel the water of crystallization. It ought to be in the state of impalpable powder. It is composed of 33 acid, 32 oxide, and 35 water. It is decomposed by the alkalies and earths, the alkaline carbonates, borates, and phosphates, and several metallic salts.

The oxide may be obtained very readily from this salt, for the purpose of fire-works, by dissolving it in water, and adding a solution of caustic potassa; collecting the precipitate, and drying it in a moderate heat. This will expel the water that may be contained in it; as metallic precipitates, made in this way, are more or less in the state of hydrates.

When metallic copper is required, it may be obtained in fine powder, and very expeditiously, by immersing a plate of iron in a solution of any of the salts of copper, as the sulphate. It will precipitate on the iron, and gradually fall to the bottom of the vessel. This metallic copper will be found to be much more impalpable than the filings, however fine, and, for that reason, may be mixed more accurately with different substances.

Copper burns with a beautiful green flame, and deposites a loose greenish-gray oxide. The ammonia-oxalate of copper, of which there are three sub-species, burns with flame.

_Sec. LVII. Of Nitrate of Copper._

This preparation of copper is used in some fire-works. It communicates a green colour to flame. When combined with carbonaceous substances, the combustion is vivid. This is owing to the decomposition of the nitric acid, (in the same manner as the acid of nitrate of potassa and other nitrates is decomposed), during which carbonic acid and deutoxide of azote are produced. Nitrate of copper has been more particularly recommended for the preparation of match stick, similar to that of M. Cadet, and of match rope. It is used in the same manner as the nitrate of lead. M. Proust used it in lieu of nitrate of lead when repeating some experiments of M. Born. It is more expensive than the acetate, or even the nitrate of lead. Its effect, however, is the same.

Nitrate of copper attracts the moisture of the atmosphere, and deliquesces. Acetate of lead, on the contrary, by exposure to the air gradually effloresces, and in time is decomposed. The preparations of lead, for that reason, are preferable to the nitrate of copper.

Nitrate of copper is formed by dissolving copper in nitric acid; and, when the acid is saturated, the requisite quantity of water may be added. The salt may be obtained in a dry state by evaporation; and, after being dissolved in water, the wood or rope may be soaked in it.

Dry nitrate of copper, wrapped up in tin-foil, will produce no action; but, if water be added, sufficient to moisten it, and then the foil closed tightly, combustion will take place. The water promotes chemical action by dissolving the nitrate of copper, which is then decomposed by the tin, and the quantity of caloric, put in a distributable state, is sufficient to inflame the tin. The details of the rationale will be given hereafter.

The ammonia-nitrate of copper is fulminating copper. The chlorate of copper is a deflagrating salt. Ammonia added to nitrate of copper, first separates an oxide, and then dissolves it. It is more than probable, that nitrate of ammonia causes the ammonia-nitrate to explode.

_Sec. LVIII. Of Strontia._

The earth called strontia or strontian, is found abundantly in different parts of the world, in combination with carbonic and sulphuric acids. The carbonate of strontia or strontianite, effervesces with acids, and burns with a purple flame. It contains about 60 or 70 per cent. of earth. The sulphate of strontia, or celestine, contains about 57 of strontia.

When carbonate of strontia is mixed with charcoal powder, and exposed to a heat of 140° of Wedgwood's pyrometer, the carbonic acid will be expelled, and pure strontia remain. The earth may be obtained in a pure state, by dissolving the carbonate in nitric acid, and evaporating the solution until it crystallizes, and exposing the crystals, in a crucible, to a red heat, until the nitric acid is driven off. If the carbonate cannot be had, the sulphate may be employed. For this purpose, it is to be pulverized and mixed with an equal weight of carbonate of potassa, and boiled in water. The carbonate of strontia, thus obtained, which exists in the form of a powder, is to be treated with nitric acid as already described.

Strontia, like the other earths, is a compound body, having a metallic basis, called _strontium_, which, united with oxygen, forms the earth.

The specific gravity of strontia approaches that of barytes. Like pure barytes, it is soluble in water, forming strontia water. It requires rather more than 160 parts of water at 60° to dissolve it; but much less of boiling water.

The solution of strontia in water, when evaporated, will crystallize in thin, transparent, quadrangular plates, generally parallelograms, seldom exceeding a quarter of an inch in length. These crystals contain about 68 per cent. of water; and are soluble in little more than twice their weight of boiling water, and in 54.4 times their weight of water at 60°. When dissolved in alcohol, they give a blood-red colour to its flame. The solution of strontia changes vegetable blues to green. Strontia differs from barytes in being infusible, much less soluble, of a different form, weaker in its affinities, and not poisonous.

The metallic base of strontia, which was discovered by Sir H. Davy, in 1808, when exposed to the air, or when thrown into water, rapidly absorbs oxygen, and is converted into strontia.

As strontia communicates a red colour to flame, it has been used in certain compositions of artificial fire. The brilliant red fire, sometimes used in theatres, owes its colour to this earth. See _Theatrical fire-works_. Muriate and nitrate of strontia will give a red or purple colour to the flame of alcohol. See _coloured flame of alcohol_.

If a piece of cloth be dipped in a solution of muriate, nitrate, or acetate of strontia, or in strontia water, and then immersed in alcohol, it will burn with a red flame.

M. Fourcroy, (_Système des Connaissances Chimiques, &c._ tome iii,) mentions the use of nitrate and muriate of strontia, in artificial fire-works, for the purpose of communicating a red colour to the flame of combustible bodies. Since that time, the nitrate, in particular, has been recommended and used.

One of the characters of the salts of strontia, is, that they give a red flame to burning bodies; whereas the salts of barytes or of lime, used in the same manner, communicate a yellow flame.

The saline combinations of strontia were examined with particular attention by Dr. Hope. See _Edinburg Philosoph. Transactions_ for 1790.

Nitrate of strontia may be formed by dissolving carbonate of strontia, or the sulphuret obtained by decomposing the sulphate by charcoal, in nitric acid, filtering the solution, evaporating it, and suffering it to crystallize.

Nitrate of strontia deflagrates on ignited coals. Dr. Hope pointed out, that if nitrate of strontia be exposed to a red heat, and a combustible substance be, at this time, brought in contact with it, a deflagration, with a very vivid red flame, will be produced. When a crystal of this salt is put into the wick of a candle, it communicates a beautiful purple flame. It does not deliquesce in the air, and, therefore, the compositions, into which it enters, cannot spoil on that account. Nicholson (_Chemical Dictionary_,) observes, that nitrate of strontia may be used in the art of pyrotechny. For this purpose, however, it is mixed with sulphur, chlorate of potassa, and sulphuret of antimony; and sometimes with the addition of sulphuret of arsenic and charcoal, as in the _red fire_ for theatrical uses.

The muriate of strontia has similar properties. Davy first observed, that when strontia was heated in chlorine gas, it gave out oxygen gas, and a chloride of strontium was formed.

Muriate of strontia is formed very readily, by dissolving the carbonate or sulphuret of strontia in muriatic acid, and evaporating the solution in order to obtain crystals. These crystals are very soluble in water. They are soluble, also, in twenty-four times their weight of pure alcohol, at the temperature of 60°. This alcoholic solution, we remarked, burns with a fine purple colour. These crystals suffer no change when exposed to the air, except they be very moist; in which case, they deliquesce. When heated, they first undergo the watery fusion, and are then reduced to a white powder. Fourcroy recommends the muriate of strontia for fire-works.

Carbonate of strontia, when thrown in powder on burning coals, produces red sparks.

Acetate of strontia, another salt used in fire-works, is formed by dissolving strontia, or its carbonate, in acetic acid. It will crystallize. The crystals are not affected by exposure to the air. When heated, its acid is decomposed, as happens to all the other acetates.

_Sec. LIX. Of Boracic Acid._

Borate of soda, or borax, is a salt, which has long been known, and is used chiefly in the arts as a flux for the fusion of bodies, and for soldering. Boracic acid is a compound body, consisting of a newly discovered substance, called boron, and oxygen. Homberg obtained the acid from borax in 1702, by distilling a mixture of borax, and sulphate of iron. He supposed that it was a product of the latter; and hence it was called the _volatile narcotic salt of vitriol_, or _sedative salt_.

Boracic acid forms two salts with soda; the borate, properly so called, and borax. It is supposed to be our borax, that Pliny mentions under the name _crysocolla_, so called by the ancients. Others, however, assert, that their crysocolla was nothing more than the rust of copper, triturated with urine. The impure borax in the East Indies, is called _tincal_. When borax is melted, and exposed for some time to heat, it loses its water, and is changed into what is known by the name of _calcined borax_.

The easiest process for obtaining boracic acid is to make a concentrated solution of borax in hot water, and add by degrees, sulphuric acid, which will unite with the soda; and, as the fluid cools, the boracic acid will separate in shining laminated crystals. No more acid should be added than is sufficient to make the solution slightly sour. The crystals are to be washed with cold water, and drained upon brown paper.

One of the principal characters of boracic acid is, that it is very soluble in alcohol, to the flame of which it communicates a green colour. Paper dipped in this solution, burns in the same manner.

In consequence of this property of imparting a green colour to flame, I made some experiments with it, for the purpose of preparing _green fire_; and found, that, by employing it in the proportion of one-eighth, the flame was always green, provided that the flame of the combustible used, was not tinged of any other colour. Nitre, charcoal, and boracic acid will give a green; also nitre, lamp oil, and boracic acid; nitre, alcohol, and boracic acid, along with charcoal; and chlorate of potassa, charcoal, and boracic acid, with or without the addition of alcohol. But, although boracic acid communicates a lively green, its expense will prevent its use in that way, especially as many other preparations, as those of copper, will have the same effect, and are more economical on account of their price. See the _Coloured Flame of Alcohol, and Coloured Fire_.

Oils, when assisted by heat, will dissolve boracic acid. In naphtha, it is very soluble. With oils, it yields fluid and solid products, which give a green colour to the flame of alcohol. It is not a combustible acid, but only imparts colour to the flame of combustible bodies.

Boron will unite with fluorine, the radical of fluoric acid. When one part of vitrified boracic acid, two of fluate of lime or fluor spar, and twelve of sulphuric acid are distilled, an acid gas will be obtained, called fluo-boric gas. For the properties of boron, consult Thenard's _Traité de Chimie_.