CHAPTER III.

OF PORTABLE FIRE-WORKS.

_Sec. I. Of exhibitions on Tables._

Fire-works, it is obvious, may be employed in a variety of ways, either large or small, in the open air, or in apartments, according to circumstances. _Fire-tables_ are composed of a great many works, the same as is exhibited upon a large scale; but of a size corresponding with small exhibitions. As _fire-tables_ are used only in apartments, and the works are shown from tables, on which they are arranged, it is necessary that the cases which contain them should be of a small caliber, and their fire less extensive.

The cases or cartridges are made of one-eighth of an inch in diameter, and charged with the best pistol powder, which produces less _smoke_ than cannon powder. These small works are usually exhibited on pasteboard, differently arranged.

Among the works are frequently figures, resembling fruit contained in _gerbes_ and even small _caprices_. _Pinks_, which are also used, are generally modified, or accompanied with other decorations, and furnished with illuminated suns. _Fire-pots_ of one inch in diameter, filled with small _bombs_ and various devices, are employed, when a _surprise_ is intended. The fire-table is arranged, although upon a small scale, in the same manner as other works. Their arrangement, therefore, is the same as for other kinds of fire-works, only proportioning them accordingly.

_Brilliant fire._

Meal powder, 16 oz. Fine filings of steel. 2½ do

_Jessamine._

Meal powder, 16 oz. Saltpetre, ½ -- Sulphur, ½ -- Fine steel filings, 2½ --

_Aurora._

Meal powder, 16 oz. Gold powder, 2 --

_White._

Meal powder, 16 oz. Saltpetre, 6 -- Sulphur, 10 --

_Rays._

Meal powder, 16 oz. Needle filings, (or filings of the best steel,) 1½ --

_Silver rain._

Meal powder, 16 oz. Saltpetre, ½ -- Sulphur, ½ -- Needle filings, (or filings of the best steel,) --

_Chinese silver rain._

Meal powder, 18 oz. Sulphur, 2 -- Saltpetre, 1 -- Powder of cast iron, of the best, 5 --

As to _aquatic fire-works_, some of which are frequently shown in rooms, the reader will find in the article on that subject, a full account of the manner of forming them. He may also consult a treatise on _Artificial fire-works_ by Perrint D'Orval, published in 1745. This work gives ample instructions for performing all kinds of fire-work on water.

In the article alluded to will be found several formulæ for preparing odoriferous fire, which may be used for exhibitions on the table. The succeeding chapter, however, is sufficiently comprehensive on that subject.

_Sec. II. Of Table Rockets._

Table rockets are not calculated for exhibition. They are designed merely to show the truth of driving, and the judgment of a fire-worker. They have no other effect, when fired, than spinning round in the same place where they began, till they are burnt out, and showing a horizontal circle of fire. The method of making these rockets, is the following: Have a cone, turned out of solid wood, 2-1/2 inches in diameter, and of the same height, and, round its base, draw a line. On this line, fix four spokes, two inches long each, so as to stand one opposite the other; then fill four nine-inch one pound cases with any strong composition, within two inches of the top. These cases are made like tourbillons, and must be rammed with the greatest exactness. The rockets being filled, fix their open ends on the short spokes; then, in the side of each case, bore a hole near the clay. All these holes or vents must be so made, that the fire of each case may act the same way; and from these vents carry leaders to the top of the cone, and tie them together. When the rockets are to be fixed, set them on a smooth table, and light the leaders in the middle, and all the cases will fire together, and spin on the point of the cone. These rockets may be made to rise, like tourbillons, by making the cases shorter, and boring four holes in the under side of each, at equal distances. This being done, they are called double tourbillons.

All the vents in the under sides of the cases, must be lighted at once; and the sharp point of the cone cut off, at which place, it is to be made spherical.

_Sect. III. Of the Transparent Illuminated Table Star._

The table star is usually twelve feet in diameter, and, from the nearest extremity to the frame, four feet. This proportion, observed on each side, will make the centre frame four feet square. In this square, a transparent star is fixed. This star may be painted blue, and its rays made like the flaming stars. The wheels for this star may be composed of different coloured fires, with a charge or two of slow fire. The wheels, on the extremities, may be clothed with any number of cases; so that the star-wheel consists of the same. The illuminated fires, which must be placed very near each other on the frames, in order to have a proper effect, ought to burn as long as the wheels, and be lighted at the same time.

_Sect. IV. Of Detonating Works._

We have noticed various fulminating preparations in different parts of our work, such as the ordinary fulminating powder, Higgins's fulminating powder, fulminating oil, and several metallic powders. We have also given some preparations made with fulminating silver, the making of which we have noticed.

Besides the torpedo, &c. prepared with fulminating silver, there are some other preparations made with the same substance, which we purpose to give in this place.

_Waterloo crackers._ Take a slip of cartridge paper, about three-quarters of an inch in width, paste and double it. Let it remain till dry, and cut it into two equal parts in length, (No. 1 and 2), according to the following pattern.

+-----------+-----------+--+----------+----------------+ | No. 1. | Glass. |S.| Glass. | No. 2. | +-----------+-----------+--+----------+----------------+

Take some of the glass composition, and lay it across the paper as in the pattern, and put about a quarter of a grain of fulminating silver in the place marked S.; and, while the glass composition is moist, put the paper, marked No. 2, over the farthest row of glass. Over all, paste, twice over the part that covers the silver, a piece of paper; let it dry. By pulling both ends apart, the friction by the glass, will cause the fulminating silver to explode.

_Detonating Girdle._ Procure a piece of girth, from 12 to 18 inches in length. Double it, and fold it down about 1-1/2 inches, similar to the fold of a letter, and then turn back one end of the girth, and it will form two compartments. Then dissolve some gum arabic in water, and thicken it by adding coarsely powdered glass. Place two upright rows of the glass composition, in the inside of one of the folds, about a quarter of an inch in width, and, when they are dry, sow the first fold together on the edge, and then the second at the opposite end; so that one end may be open. Then in the centre of the two rows, put about a grain of fulminating silver, and paste a piece of cotton or silk over it. Make a hole at each end of the girdle, and hang it to a hook in the door post, and the other hook on the door; observing to place the silk part, so that it may come against the edge of the door upon being opened, which will occasion a report.

_Detonating Tape._ This is made of binding, about 3/8ths of an inch in width. The same directions are to be attended to, as those we have just given for making the girdle. It may be exploded by taking hold of each end, and rolling the ends from each other sharply, or by two persons pulling at opposite ends.

_Detonating Balls._ These are made in several ways, either by enclosing a shot in paper with fulminating silver, which is exploded by throwing it on the ground, or made of small glass globes. For the latter, procure some small glass globes, between the size of a pea and a small marble, in which there must be a small hole; put into it half a grain of fulminating silver, and paste a piece of paper over the hole. When this ball is put on the ground, and trod upon, it will go off with a loud noise. If put under the leg of a chair, and pressed by the weight of the body, the same effect will take place.

_Detonating Cards._ Take a piece of card, about three fourths of an inch in breadth and 12 in length; slit it at one end, and place in the opening a quarter of a grain of fulminating silver, close the end down with a little paste, and when dry light the end in a candle.

Fulminating silver may be used in several other ways, affording a variety in the effect, as the following: Fold a letter in the usual manner, and along with the wafer introduce the fulminating silver mixed with some glass: when the wafer is broken, in the act of opening the letter, a violent explosion will take place.

By placing a quarter of a grain of the powder in the midst of some tobacco in a pipe, or between the leaves of a segar, and closing the end again to prevent the powder from falling out; it need hardly be stated, that on lighting it, an explosion ensues. Such experiments should be made with caution.

One-third of a grain of fulminating silver, folded in a small piece of paper, and wrapped in another piece, then pasted round a pin, which is to be stuck in the wick of a candle, will make a loud report.

As fulminating silver explodes by heat, or friction, it is obvious, that various contrivances may be used for this purpose. If, for instance, half a grain be put on a piece of _glass paper_, (paper covered with a mixture of powdered glass and gum), then inclosed in a piece of tin foil, and put in the bottom or side of a drawer; on opening or shutting it, the powder will immediately explode. The same effect takes place by putting a quarter of a grain into a piece of paper, and placing it in the snuffers. When the candle is snuffed, it will go off.

Two figures, one of which blows out and the other relights a candle, are sometimes exhibited in rooms. This is performed by making two figures of any shape or material, and inserting in the mouth of one, a small tube, at the end of which is a piece of phosphorus, and in the mouth of the other, a tube containing at the end a few grains of gunpowder; observing that each be retained in the tube by a piece of paper. If the second figure be applied to the flame of a taper, it will extinguish it, by reason of the gunpowder, and the first will light it again.

_Candle bombs._ These are usually called candle crackers, and are made of glass. They are blown in small bubbles, having a neck about half an inch long, with very slender bores, by means of which a small quantity of water or spirit of wine is introduced. The orifice is then closed. When they are stuck into a candle, the heat converts the water or alcohol into vapour, which breaks the glass with a loud report, extinguishing the flame at the same time.

_Detonations by Electricity._ The electric fluid, it is known, will inflame combustible bodies, and, for the purpose of experiment, several contrivances have been used. That of placing the substance, gunpowder for instance, on a small insulated stand, and passing the spark through it by means of conductors, will cause its inflammation. The _electrical house_ is also an exemplification of the effect of the electric fluid.

_Detonations by Galvanism._ Substances, placed on a glass plate, and brought in contact with the positive and negative poles of a galvanic battery, are readily inflamed. Hence phosphorus, gunpowder, the metals, &c. may be inflamed in this manner. The deflagrator of professor Hare of the University of Pennsylvania, is a powerful apparatus for the purpose; for the construction of which, and the details of its effects, see the American Journal of Science by professor Silliman, of Yale College.

Among the means of producing heat that of compression is well known. The common condensing syringe, for inflaming spunk or touch paper, is on this principle.

This syringe is now made very portable, not more than six inches in length and about three-eighths of an inch in diameter. The end of the piston, which fits tight in the cylinder, has a small cavity, in which the spunk is put, so that, when the piston is suddenly compressed, the air is condensed, and a temperature produced, sufficient to inflame it. The air, in the cylinder, is condensed in the ratio of about one to forty. The calculations on the degree of compression, which atmospheric air must undergo to produce fire by this kind of percussion, with observations on the subject, may be seen in M. Biot, (_Traité de Physique Experimentale, &c._ tome ii, p. 17), with other remarks concerning the sources of caloric.

To account for certain phenomena in the atmosphere, some of which are accompanied with detonations, Mr. Nicholson (_Chemical Dictionary_, article Air, atmospherical), conceives that the lower atmosphere consists chiefly of oxygen and nitrogen, together with moisture, and the occasional vapours or exhalations of bodies. The upper atmosphere seems to be composed of a large proportion of hydrogen, a fluid of so much less specific gravity than any other, that it must naturally ascend to the highest place; where, being occasionally set on fire by electricity, it appears to be the cause of the aurora borealis and fire-balls. It may easily be understood, that this will only happen on the confines of the respective masses of common atmospherical air, and of the inflammable air; that the combustion will extend progressively, though rapidly, in flashings from the place where it commences; and that, when, by any means, a stream of inflammable air, in its progress towards the upper atmosphere, is set on fire at one end, its ignition may be much more rapid than what happens higher up, where oxygen is wanting; and at the same time more definite in its figure and progression, so as to form the appearance of a fire-ball.

Detonations frequently accompany combustion. There are many interesting experiments on this subject, some of which we will notice in this place, _viz._

_Experiment 1._ If a small portion of fulminating powder be placed on a fire-shovel over a hot fire, it will become brown, then melt, and swell up, and finally explode. See _Fulminating powder_.

_Experiment 2._ Iron filings and sulphur, made into a paste with water, and buried in the ground for a few hours, will unite, decompose the water, and inflame; throwing up the earth with violence and noise. See _Artificial Volcano_.

_Experiment 3._ If nitrate of copper be spread on tin foil and wetted, and the foil immediately wrapped up, scintillations of fire will follow, accompanied with slight detonations.

_Experiment 4._ Five or six grains of sulphuret of antimony, with half its weight of chlorate of potassa, when struck with a hammer will cause a loud detonation.

_Experiment 5._ Two grains of chlorate of potassa, and one grain of flowers of sulphur, when rubbed together, will produce a detonating noise; and the same mixture, struck with a hammer, will give a loud report. See _Chlorate of Potassa_.

_Experiment 6._ One grain of phosphorus and two grains of chlorate of potassa, struck in the same manner, will produce a violent explosion. See _Phosphorus_.

_Experiment 7._ Mix ten grains of chlorate of potassa with one grain of phosphorus, and drop the mixture into sulphuric acid; detonation and flame will be the consequence.

_Experiment 8._ Make a mixture of arsenic and chlorate of potassa. On presenting a lighted match, combustion, accompanied with a detonation, will ensue; and, if a train of gunpowder be laid, and both inflamed at the same time, the arsenical mixture will burn with the rapidity of lightning, while the other burns with comparative slowness.

_Experiment 9._ If one grain of dry nitrate of bismuth be mixed with one grain of phosphorus, and rubbed together in a metallic mortar, a loud detonation will be produced.

_Experiment 10._ If a globule of potassium be thrown upon water, an instantaneous explosion will be produced.

_Experiment 11._ A grain of fulminating gold, struck gently with a hammer, will produce a loud explosion.

_Experiment 12._ A few grains of fulminating mercury, struck in the same manner, will produce a loud detonation.

_Experiment 13._ When a grain or two of potassium are mixed with the same quantity of sodium, no effect will take place; but if the mixture be brought in contact with a globule of mercury, and agitated, combustion, with a slight detonation, will follow, showing the vivid combustion of three metals, when brought in contact with each other.

_Experiment 14._ If to six grains of chlorate of potassa, we add three grains of pulverized charcoal, and rub the two in a mortar, no effect will ensue; but if we add to this mixture two grains of sulphur, and continue the rubbing, inflammation, accompanied with a report, will take place. See _Gunpowder of chlorate of potassa_.

_Experiment 15._ Chlorate of potassa and sulphur, rubbed in a mortar, will produce a crackling noise, similar to that of a whip. These reports will follow in succession as the pestle is pressed on the mixture.

_Experiment 16._ Combustion, with a slight detonation, takes place during the melting of coin in a nut-shell. For this purpose, make a mixture of three parts of nitre, one part of sulphur, and one of very fine dry saw dust; press a small portion of this powder into a walnut shell, and put on it a small silver or copper coin, rolled up, and fill the shell with the mixture. If the mixture be now inflamed, it will melt the coin in a mass, while the shell will be only blackened.

_Experiment 17._ Introduce, into an inflammable air pistol, a mixture of hydrogen gas with oxygen gas, or, in the place of the latter, atmospheric air, and apply a lighted taper: a violent detonation will be produced. See _Inflammable air works_.

_Experiment 18._ Mix some fine musket powder with pulverized glass, and strike the mixture with a hammer on an anvil; the gunpowder will explode. See _Gunpowder_.

_Experiment 19._ Take a small portion of fulminating platinum, and place it on the end of a spatula, or on the blade of a knife, and hold it over the flame of a candle; a sharp explosion will take place. See _Fulminating platinum_.

_Experiment 20._ If soap bubbles be formed of a mixture of hydrogen gas and atmospheric air, and touched with a lighted taper, they will detonate in the air.

_Experiment 21._ If a portion of detonating oil, (_Chloride of azote_) be heated to 212°, a violent explosion will ensue; or,

_Experiment 22._ If a portion of the same oil, of the size of a pin-head, be brought in contact with olive oil, the effect will be still more violent. See _Detonating oil_.

_Experiment 23._ Take ten or fifteen grains of _Higgins's_ fulminating powder, and expose it to heat on a shovel: detonation will follow. See _Higgins's Fulminating powder_.

_Experiment 24._ If oxalate of mercury, to the amount of three or four grains, be struck with a hammer, a detonation will ensue, in the same manner as with the nitrous etherized oxalate of mercury, or Howard's fulminating mercury. See _Mercury_.

_Experiment 25._ Take some of the detonating powder, prepared from indigo, and wrap it up in paper, and strike the paper with a hammer: an explosion will ensue. See _Detonating powder from indigo_.

_Experiment 26._ If some gunpowder be placed on the stand of an electrical discharger, and the electric spark passed through it, combustion, with a detonation, will be produced.

_Experiment 27._ If some gunpowder be wrapped in tin foil, and placed on a glass plate, and the two wires of a galvanic battery brought in contact with the foil; the foil will inflame and explode the powder.

_Experiment 28._ Mix in a mortar one part of sulphuret of potassa with two parts of nitrate of potassa, and expose the mixture to the action of heat in the same manner as fulminating powder: a violent detonation will take place. The sulphuret of potassa is recommended, in lieu of potassa and sulphur in a separate state; and although called Bergman's fulminating powder, this compound is in fact, according to the theory of its explosion, the same as the ordinary fulminating powder.

_Experiment 29._ If, says Morey, (_Silliman's Journal_ ii, 21), a given quantity of strongly compressed boiling water, be suddenly discharged into about an equal quantity of oil or rosin, at or near the boiling point, it will explode, to every appearance, as quickly and violently as gunpowder.

_Experiment 30._ If zinc or iron filings, or pulverized antimony, be mixed with chlorate of potassa, and struck with a hammer, violent detonations will ensue. If sulphuret of iron be used, the same effect will ensue. See MM. Fourcroy and Vauquelin's communication to the _Société Philomatique_, in their _Transactions_.

_Experiment 31._ If oxide of mercury, obtained from its solution in nitric acid by means of caustic potassa, be dried, and mixed with flowers of sulphur, and struck with a hammer, a detonation will be produced. (See _Journal de Physique_, 1779.)

_Experiment 32._ If alcohol or ether be mixed with chlorate of potassa, into a thick paste, and the mixture struck with a hammer, an explosion will be the consequence: or,

_Experiment 33._ If, instead of alcohol or ether, we make use of fixed or volatile oils, and proceed in the same manner, the same effect will ensue.

_Experiment 34._ If a small portion of chloride of azote (_Detonating oil_) be dropped into a solution of phosphorus in ether or alcohol, a violent explosion will take place: or,

_Experiment 35._ If in the place of phosphorized ether, other oils, as camphorated oil, palm oil, whale oil, linseed oil, sulphuretted oil, oil of turpentine, naphtha, &c. be brought in contact, the same effect will ensue.

_Experiment 36._ Chloride of azote will also detonate with sundry gaseous and solid substances, as supersulphuretted hydrogen, sulphuretted hydrogen, phosphuretted hydrogen, nitrous gas, aqueous ammonia, phosphuret of lime, ambergris, fused potassa, and sundry metallic soaps. Messrs. Porret, Wilson, and Kirk, brought one hundred and twenty-five substances in contact with it, and twenty-eight of the number produced detonations. (_Nicholson's Journal_, vol. 34.)

_Experiment 37._ If a small quantity of ammoniacal nitrate of copper be wrapped in paper, or in a piece of tin foil, and struck with a hammer, a detonation will ensue.

_Experiment 38._ If a small portion of arsenic and chlorate of potassa be mixed, and smartly struck, a flame will be produced, accompanied with an explosion; or,

_Experiment 39._ If the same mixture be touched with a lighted match, it will burn with considerable rapidity; or,

_Experiment 40._ If it be thrown into concentrated sulphuric acid, at the instant of contact, a flame will rise into the air like a flash of lightning.

_Experiment 41._ Heat a portion of deutoxide of chlorine: when the temperature arrives at 212°, an explosion will take place, and chlorine and oxygen be evolved.

_Experiment 42._ If prussine gas, otherwise called cyanogen, or carburet of azote, be mixed with atmospheric air, in the proportion of about one to four in volume, and the electric spark made to pass through the mixture; a violent detonation will result, leaving a mixture of carbonic acid gas and azotic gas.

_Experiment 43._ If a mixture of equal parts of nitrate of potassa, and titanium, be thrown into a red-hot crucible, detonation will follow.

_Experiment 44._ Melt some nitrate of potassa in a crucible, and bring it to the state of ignition: now throw in a small quantity of pulverized zinc, and a very violent detonation will take place.

_Experiment 45._ If one part of zinc filings and two parts of dry arsenic acid be distilled in a retort, or exposed to heat in a crucible, the moment it becomes red, a detonation will be produced.

_Experiment 46._ If a few drops of deutoxide of hydrogen, or the oxygenized water of Thenard, be let fall on dry oxide of silver, a violent action will follow, accompanied with an explosion. Several other oxides have the same effect.

_Experiment 47._ If a portion of black wadd, an ore of manganese found in Derbyshire, England, be brought in contact with linseed oil; the oil will take fire, producing sometimes slight detonations.

_Experiment 48._ Take a portion of the brown oxide of tungsten, formed by transmitting hydrogen gas over tungstic acid, in an ignited glass tube; mix it with chlorate of potassa, and strike the mixture with a hammer: a loud detonation will ensue; or,

_Experiment 49._ Heat some of the brown oxide in the air. It will take fire, and burn like tinder, passing to the state of the yellow oxide, or tungstic acid.

_Experiment 50._ If one measure of oxygen gas, and two measures of hydrogen gas be mixed in the explosive eudiometer, and the electric spark passed through them, a detonation will ensue, and a complete condensation take place.

_Experiment 51._ When equal volumes of protoxide of azote, or gaseous oxide of azote, (called also nitrous oxide), and hydrogen gas, are treated in the same manner, the mixture will explode, leaving a residuum, consisting of azotic gas.

_Experiment 52._ If two measures of carbonic oxide or gaseous oxide of carbon, and one measure of oxygen, be submitted to the action of the electric spark, a detonation will ensue, and the carbonic oxide will be changed into carbonic acid.

_Experiment 53._ If one measure of carburetted hydrogen gas, either the heavy or light carburetted hydrogen, called also the hydroguret and bi-hydroguret of carbon, (the former being sometimes called olefiant gas), be mixed with two or three measures of oxygen gas, and the electric spark transmitted through them; a detonation will ensue, forming water and carbonic acid.

_Experiment 54._ If one measure of cyanogen, (carburet of azote), be mixed with two and a half measures of oxygen gas, and treated with the electric spark, the mixed gases will explode very loudly. The cyanogen burns, in this case, with a blue flame; although it is usually of a purple colour. The products of combustion are carbonic acid and azote. (See Experiment 42.)

_Experiment 55._ If one measure of arsenuretted hydrogen gas, (obtained from an alloy of three parts of tin and one of arsenic, by treating it with muriatic acid), and two measures of oxygen gas are mixed together, and the electric spark is passed through the mixture; a detonation will ensue, and water and arsenious acid be formed.

_Experiment 56._ If potassium be made to act upon a compound of chlorine and sulphur, called chloride of sulphur, an explosion will immediately ensue; but,

_Experiment 57._ If potassium be dropped into chlorine gas, inflammation only will take place, accompanied with a vivid light, forming chloride of potassium, (dry muriate of potassa.)

_Experiment 58._ If sulphuret of potassium be heated in the air, it will burn with great brilliancy, forming sulphate of potassa; but, if mixed with chlorate of potassa, and struck with a hammer, a violent detonation will be produced.

_Experiment 59._ If potassium be heated in sulphuretted hydrogen gas, it takes fire, and burns with a vivid flame, and pure hydrogen is set free; thus proving that sulphuretted hydrogen gas, although inflammable itself in oxygen gas, is a supporter of combustion for potassium.

_Experiment 60._ If phosphuret of potassium be exposed to the air, it will inflame spontaneously, forming phosphate of potassa; but if it be dropped into water, it will produce a violent explosion, in consequence of the immediate disengagement of phosphuretted hydrogen gas.

_Experiment 61._ If potassium be moderately heated in the air, it inflames, burns with a red light, and emits alkaline fumes.

_Experiment 62._ If potassium be thrown upon water, it acts with great violence, burning with a beautiful light, of a red colour, mixed with purple, the water becoming a solution of potassa.

_Experiment 63._ When sodium is heated strongly in oxygen or chlorine, it burns with great brilliancy; but it does not inflame, when thrown into water. It is converted, however, into soda. If it be heated in oxygen gas in excess, it burns, and is converted into the peroxide of sodium, which, when mixed with combustible bodies, and exposed to the action of heat, deflagrates with violence, giving off its excess of oxygen, and becoming changed into soda, or protoxide of sodium.

_Experiment 64._ When sulphuret of sodium is mixed with chlorate of potassa, and struck with a hammer, a detonation will ensue; and when sodium is heated nearly to fusion, in contact with sulphuretted hydrogen gas, it will unite with the sulphur; flame will be produced, and hydrogen gas set at liberty. A sulphuret of sodium is thus formed, which is usually combined with some sulphuretted hydrogen.

_Experiment 65._ When a mixture of ammoniacal gas, in a dry state, and oxygen gas, is submitted to the influence of the electric spark, in the explosive eudiometer, explosion will take place, and water and azotic gas result.

_Experiment 66._ If potassium or sodium be heated in fluoric gas, a rapid combustion takes place, in all respects as brilliant as in oxygen gas.

_Experiment 67._ If gallic acid be placed on a red-hot iron, it burns with flame, and emits an aromatic smell, similar to that of benzoic acid; but, if mixed with chlorate of potassa and struck with a _hot_ hammer, a detonation will ensue. Various vegetable acids, as the benzoic, which is highly inflammable, produce similar effects.