Chapter II (2)

When oxygen gas is presented to azote at the moment of its liberation, nitric acid is formed. As ammonia is the result of animal putrefaction, or is formed in the process, hydrogen must unite also with azote. The azote is furnished by the animal substances. These facts being known, we are enabled to account for the generation of nitric acid, and, consequently, of the earthy and other nitrates, in artificial nitre beds.

In noticing this subject, it is unnecessary to quote the opinion of Stahl, who believed that there was but one acid in nature, the sulphuric; and that nitric acid was the sulphuric acid, combined with phlogiston, which he affirmed was produced by putrefaction; nor is it necessary to mention the opinion of Lemery, who believed that nitre exists ready formed in animals and vegetables by the processes of vegetation and animalization. The experiments of the French philosophers have put these opinions at rest.

Thouvenal discovered, that nothing more was necessary for the production of nitre than a basis of lime, heat, and open air; so that nitre beds, formed of putrefying animal and vegetable substances, with the conditions thus stated, must produce saltpetre; a fact which experience abundantly justifies.

The process for the formation of nitre, is called _nitrification_.

Although animal substances, by putrefaction, furnish azote, and nascent azote unites with facility with the oxygen of the atmosphere, by which nitric acid is generated--(hence the spontaneous decomposition of nitre composts)--yet Vauquelin is of opinion, that the presence of calcareous or alkaline substances is indispensable, and that the production of carbonate of ammonia from the animal matter, is another compound, which results from the same decomposition. Ammonia is produced by the union of azote and hydrogen, and carbonic acid by that of carbon and oxygen. He considers then, that the presence of lime, magnesia, potash, &c. _determines_ the union of the azote with oxygen, and of course, the formation of nitric acid; and as this acid unites with one or other of these substances, according to circumstances, we have either nitrate of lime, or of magnesia, or nitrate of potassa. The idea that water is decomposed in the change which animal and vegetable substances undergo, in the process of nitrification, is contrary to observation; for the presence of air in dry situations, is indispensable to the process.

If a compost, made up of animal, vegetable, and calcareous substances, and put in small beds or heaps, and covered with a shed open at both sides, be frequently turned to admit new surfaces to the air, and occasionally moistened with urine, &c.--nitric acid will be generated as the putrefaction goes on. When this process is suffered to proceed until the decomposition is complete, and the beds then lixiviated, the quantity of nitre will be considerable. In all cases, we are to observe, that, as various earthy nitrates are produced, and mostly nitrate of lime, potash, or wood-ashes which contain this alkali, are to be used.

It was long since shown by Glauber, that a vault plastered over with a mixture of lime, wood-ashes, and cows' dung, soon becomes covered with efflorescent nitre; and that, after some months, the materials yield, on lixiviation, a considerable proportion of this salt. M. de Roder, speaking of nitrous walls, observes, that the efflorescence of nitre on them is in consequence of the stone, lime, and sand employed in the building.

What is denominated the _saltpetre rot_, is an efflorescence observed on the walls of old buildings, and on the ground. Dr. C. F. Gren, professor at Halle, in Saxony, (_Principles of Modern Chemistry_, vol. ii, p. 128), very justly remarks, that, among the matters capable of corruption, those are the most convenient in making nitre, which contain the greatest portion of azote, of which animal substances are the first; among which he enumerates flesh, blood, skins, excrements of animals, old woolen stuffs, and urine. He also mentions marsh plants, green herbs, mud from streets trodden by cattle, and the ground from marshes or bogs. As a compost he adds, that the ground from church-yards, where corpses have successively, and during a long series of years, undergone corruption, would be the best for artificial nitre beds. On the subject of nitre beds, the reader may consult the _Recueil de Mémoires et de Pièces sur la formation et la fabrication du saltpetre, à Paris_, 1786, 4to. These remarks on the generation of nitre, although of more ancient date, are confirmed by James and Herman Boerhaave, (_Chemistry, &c._) Hoffman, (_de Salium Medicorum, et de Præstantissima Nitri Virtute_), Stahl, (_de Usu Nitri Medico_), Neuman, (_chemical works_), and Lewis, (_Materia Medica_)--all of whom have written more or less on the formation of saltpetre; to which we may add the observations of Parr, (_London Medical Dictionary_, vol. ii, p. 24.)

The process for extracting saltpetre from damaged gunpowder is nothing more than putting it into a boiler, and adding water sufficient to cover it. On applying heat, the nitre will be dissolved. If any scum forms, it must be removed. When the solution is effected, pour it on a sufficient number of filters, and collect the fluid which passes through. The residue may be treated with more water, and the whole again filtered. After boiling the solution, set it aside to crystallize. The sulphur may be recovered, by subliming the residue in a temperature not sufficient to inflame it. The charcoal may be used again for the same purpose.

Saltpetre, when properly refined, does not contain any foreign salts, and its purity may be known by a variety of experiments, as follows: make a solution of the salt in distilled water, and filter it through paper. Put a portion of it in a wine glass, and add a solution of carbonate of potassa. To another portion, add a small quantity of muriate, or in preference, nitrate of barytes. To a third portion, add nitrate of silver. If the fluid in the first glass remains clear, without any turbidness, we are to infer the non-existence of earthy salts; if turbid, that it contains lime, or some other earth, either in the form of a nitrate or muriate. The addition of oxalate of potassa to another portion of the solution will show the presence of lime by forming a precipitate, and the addition of carbonate of ammonia, and then of phosphate of soda, will indicate magnesia. If the second glass remains transparent, it shows that neither sulphuric acid, nor any of the sulphates are present. If the fluid in the third glass continues also clear, we infer that none of the muriates exist. These experiments are sufficient to show the purity of saltpetre. It would afford perhaps more satisfaction to institute also the same experiments on other samples of nitre, by which a comparison may be formed of the relative purity of each. To make an analysis of the salt, with the view to determine the proportion of the foreign substances would be altogether unnecessary for common purposes. A regularly defined crystal would, in a great measure, point out its purity. The double refined saltpetre is chemically pure. Artificers determine the purity of nitre by its flame; if white, they call it pure, if yellow, impure.

The same reagents may be used in the examination of gunpowder, as we shall notice hereafter. If a portion of powder be mixed with distilled water, the water will dissolve only the saline substances, leaving the charcoal and sulphur. When the whole is thrown on a filter, the fluid, which passes through, will contain the saltpetre, and foreign salts, if any are present. The same experiments may then be performed with the solution, and the quality of the nitre, of which the gunpowder was made, be determined. Some gunpowder absorbs a large portion of water, which is owing to the presence of deliquescent salts. These salts may be detected by proceeding in the way we have pointed out. The art of refining saltpetre is so well known of late in the United States, especially by the Messrs. Dupont of Brandywine, Delaware, that our gunpowder is of a very superior quality. I have examined various specimens of this saltpetre, and gunpowder made with it, and could not detect any of the sulphates or muriates, either alkaline or earthy. For the manufacture of gunpowder, and fire-works generally, the nitre, it may be observed, cannot be too pure.

In pyrotechny, it is necessary to have the nitre in powder. Pulverizing it in a mortar is a tedious method, if a large quantity is required for use. There is an advantage, likewise, in the mode we will describe; because the saltpetre, besides being extremely fine, is made perfectly dry. Put into a copper kettle, whose bottom must be spherical, fourteen pounds of refined saltpetre, with two quarts or five pints of water. Put the kettle on a slow fire, and if any impurities rise and form a scum, remove them; keep constantly stirring with two large spatulas, till the water evaporates, and the nitre is reduced to a powder. This will be perfectly white, and almost impalpable. If it should boil too fast, remove the kettle, and set it on wet sand, which will also prevent the nitre from adhering to the pot. It should be kept in a dry place. This process of powdering saltpetre is performed on a large scale for the manufacture of gunpowder.

_Sec. II. Of Nitrate of Soda._

This salt has been recommended in lieu of nitre, for preparing certain fire-works; but we confess, we can see no particular advantage in using it. It has the property of attracting humidity from the air, and on that account is rendered unfit for the manufacture of gunpowder. This salt is composed of nitric acid and soda. It was formerly called _cubic nitre_. It may be formed, very readily, by saturating nitric acid with soda, and evaporating the solution. It crystallizes in rhomboidal prisms. It may be formed more economically, by mixing together the solutions of nitrate of lime and sulphate of soda, filtering the mixture, and evaporating the filtered liquor. It will be sufficient to observe, that it deliquesces, or absorbs moisture, and in the fire, that its phenomena are the same as those of nitre. It does not melt so readily.

Used in the same proportion as nitre, it will form a gunpowder, which soon, however, spoils by exposure. It will, like nitre, communicate a yellow colour to the flame of alcohol. Experiments were made with this salt, with the view to the fabrication of gunpowder, by MM. Bottée and Riffault. Their conclusions, as we have stated, may be seen in their work on _gunpowder_. Professor Proust says, that five parts of nitrate of soda, with one of charcoal, and one of sulphur, will burn three times as long as common powder, so as to form an economical composition for fire-works.

The _cubic nitre_, and the _nitrum flammans_ were known, and so called, by the older chemists. The former we have seen, is the nitrate of soda, and the latter, is a combination of nitric acid and ammonia. Nitrate of soda, consists of 6.75 acid + 3.95 soda.

Nitrate of ammonia possesses the property of exploding; and, when exposed to a temperature of about six hundred degrees, is decomposed, furnishing the nitrous oxide, called also the protoxide of azote, and exhilarating gas, besides water. Nitrate of ammonia is composed of 6.75 acid + 2.13 ammonia + 1.125 water.

_Sec. III. Of Chlorate of Potassa._

This salt, formerly called hyperoxymuriate of potassa, is used for sundry preparations, and especially for experimental fire-works. It is prepared by dissolving one part of carbonate of potassa in six parts of water, and saturating it with chlorine, formerly called oxymuriatic acid gas. This operation is usually performed in a Woulfe's apparatus. The gas, as it proceeds from the retort or gas bottle, is brought in contact with, and passes through, the fluid. It is formed by pouring liquid muriatic acid on the black oxide of manganese, or by pouring sulphuric acid on a mixture of muriate of soda, and the black oxide. When the saturation is nearly complete, crystals fall down. These being dissolved in boiling water, and the solution allowed to stand, pure chlorate of potassa will be formed.

This salt is composed of 9.5, chloric acid, and 6 potassa; and chloric acid is formed of 28.87, chlorine, and 32.28, oxygen. It is to the oxygen in the salt, that its particular properties in fire-works are to be ascribed.

This salt is decomposed by all combustible bodies, and detonations generally accompany the decomposition. Hence it is used in a variety of experiments, some of which we will give.

Three parts of the salt and one of sulphur detonate when rubbed in a mortar. The same mixture, struck with a hammer on an anvil, produces a loud explosion. Phosphorus detonates with this salt either by trituration or percussion. The quantity of each should not exceed a grain. Treated in the same manner with almost all the metals, the same effect takes place. Cinnabar, antimony, pyrites, &c. produce the same effect. Nitric acid, poured on a mixture of this salt with phosphorus, produces flashes of fire. A mixture of the chlorate and white sugar, when touched with sulphuric acid, immediately inflames. Hence it is used in the preparation of pocket lights; the mixture being put on a common sulphur match, and immersed in sulphuric acid. The same preparation of sugar and chlorate of potassa, put over a tube used for firing artillery, will set fire to the priming fuse, by dropping on it sulphuric acid. Owing to this effect, M. Gassicourt (_Archives des Découvertes_), recommended a similar mixture for discharging cannon by means of this acid. As it contains a large quantity of oxygen, that gas may be obtained from it by distillation. Light decomposes it. It should, therefore, be excluded from the light.

As this salt, when mixed with inflammable substances, detonates when struck with a hammer, it has been used for the purpose of inflaming gunpowder without the use of the flint and steel. There are several formulæ given for the purpose. We remarked, when treating of the general theory of fire-works, that the Rev. Alexander Forsyth discovered a new kind of gunpowder, which inflames merely by percussion; that the gun-lock, which he contrived, was calculated for firing cannon, as well as musquetry; that it was so contrived as to hold forty primings of such powder; and that the act of raising the cock primes the piece. In his composition, each charge of priming contains no more than one-eighth of a grain of chlorate of potassa. Since that period, it appears, that the lock, as well as the powder, has been improved, although neither of them is in general use. Thenard, (_Traité de Chimie_, tome ii, p. 559, troisième édition), has given a formula for preparing a priming powder of this salt, adapted to the new lock, which is made by mixing it with 0.55 of nitrate of potassa, 0.33 of sulphur, 0.17 of the raspings of peach-wood passed through a fine sieve, and 0.17 of lycopodium, or puffball. (See _Inflammable Powder_.)

This salt also produces powerful effects with charcoal and sulphur. Three parts of it, with half a part of sulphur, and half a part of charcoal powder, produce most violent explosions. Two persons, in 1788, lost their lives by it. If this mixture be thrown into concentrated sulphuric acid, a brilliant flame is produced. Such mixtures, we are informed, will explode spontaneously. It should not, for that reason, be kept prepared. Chlorate of potassa has been used in the place of nitre, for the manufacture of gunpowder, in consequence of its decomposition by charcoal. From its explosive effects, M. Berthollet was induced to propose it as a substitute for nitre. The proportions used by Chaptal, (_Chimie Appliqué aux Arts_, tome iv, p. 198), are six parts of chlorate of potassa, one of sulphur, and one of charcoal. They are to be mixed in a marble mortar with a wooden pestle. The first experiment was made at Essone, in France, in 1788. No sooner, however, had the workmen begun to triturate the mixture, than it exploded with violence, and killed two persons.

The force of this gunpowder is greater than that of the common sort; but the danger of preparing it, and even of using it, is so great, that these circumstances will always prevent its introduction. A salt, containing so much oxygen, and so loosely combined, that even the slightest friction, in contact with inflammable bodies, will separate it, must, of necessity, prevent its use in that way.

The experiments, which were made at the arsenal at Paris, on the 27th of April, 1793, comparing the effects of muriated powder, and the superfine common powder, have given us the following results:

1st. By the eprouvette of Darcy, consisting of a cannon, which, being suspended to the extremity of a bar of iron, described by its recoil an arc, of which the degrees can be measured.

_Recoil._

2 drachms muriatic powder, 15 deg. 2/20
2 ---- do do moistened, 14 -- 1/20
2 ---- common powder, 10 -- 7/20
2 drachms common powder, 10 -- 1/20
3 ---- muriatic powder, 20 -- 9/20
3 ---- common powder, 16 -- 6/20

From these results, it appears, that, by the eprouvette of Darcy, the muriated powder, or that prepared with chlorate of potassa, gave a superiority of force of about one-fourth.

2nd. By the eprouvette of Regnier, which is repelled by the explosion, to a distance greater or less, measured by the degrees of the arc which it describes:

Muriated powder, 42
Idem, 51¾
Idem, moistened, 52
Common powder, superfine, 23
Idem, 22½

From which it results, that by the eprouvette of Regnier, the force of the powder of the oxymuriate is double that of the nitrate, or common powder.

M. Ruggieri is of opinion, that chlorate, or hyperoxymuriate of potassa may be employed with advantage in the composition of rockets, but we have not heard that it has been used. It is more powerful in its effects, and probably for this reason he recommended it. This salt, mixed with other substances, will produce the _green fire_ of the palm-tree, in imitation of the Russian fire.

Chloric acid may be obtained in a separate state, by boiling the compound solution formed by passing chlorine gas through a solution of barytic earth, with phosphate of silver, which separates the muriatic acid. By evaporation, the chlorate of barytes will crystallize in fine rhomboidal prisms. When these crystals are dissolved in water, and diluted sulphuric acid added by degrees, an acid liquid will be obtained, which, if the sulphuric acid be added cautiously, will be found entirely free from the latter acid and barytes, and not affected by nitrate of silver. This is the chloric acid dissolved in water. Chloric acid unites with sundry bases. Combined with ammonia, it forms a fulminating salt, formerly described by M. Chenevix. This salt is formed, by mixing together carbonate of ammonia, and chlorate of lime. The carbonate of lime is then separated by the filter, and the clear liquid, holding the chlorate of ammonia in solution, is evaporated. Chlorate of ammonia is very soluble in water and alcohol, and decomposed by a moderate heat.

Chlorates, as the chlorate of potassa, are formed more readily in the manner already stated: _viz._ by saturating the base with chlorine, but in this case two salts are produced, the chlorate and hydrochlorate. Chloric acid has also been obtained in a separate state, from chlorate of potassa, by a process recommended by Mr. Wheeler.

Perchloric acid, composed of seven primes of oxygen and one of chlorine, is obtained from chlorate of potassa, treated in a particular manner. Three parts of sulphuric acid and one of chlorate of potassa, when heated, will give a saline mass, consisting of bisulphate of potassa, and perchlorate of potassa. Deutoxide of chlorine will be evolved. The perchlorate detonates feebly when triturated with sulphur.

_Sec. IV. Sulphur._

Sulphur, or brimstone, is a principal ingredient in almost all the compositions of fire-works. It should, therefore, be pure. The flowers may be considered the purest kind of sulphur.

Sulphur is found native, either alone, or accompanying certain minerals, such as gypsum, rock-salt, marl, and clay, as in Switzerland, Poland, and Sicily. In the neighbourhood of salt-springs, it is also found; and frequently in water, in combination with hydrogen, forming the natural hepatic waters. It is also found on the surface of the earth, as in Siberia. Volcanic sulphur, or that which occurs in the fissures and cavities of lava, near the craters of volcanoes, is very common.

Solfatere, Sicily, the Roman states, Guadaloupe, and Quito, in the Cordilleras, are most celebrated for native sulphur. It has been found in the United States, but in no quantity. We have a number of mineral springs, which deposite sulphur. The Clifton Springs of Ontario are of this kind. It occurs abundantly, in combination with hydrogen, as sulphuretted hydrogen gas, in various parts of the United States.

Native sulphur is abundant in the island of Java. It is obtained from the now almost extinct volcano, about sixty miles from the town of Batavia. At the bottom of the crater, there is said to lie many hundred tons of native sulphur. Silliman (_Journal_, vol. i, p. 58) observes, that it is in the crater of this volcano, that the celebrated lake of sulphuric acid exists, "and from which it flows down the mountain, and through the country below, a river of the same acid."

Sulphur, however, is usually obtained from pyrites or metallic sulphurets, by fusion and sublimation. It is usually denominated by the name of the place whence it comes. Hence we have the Italian and Sicilian sulphur; the crude, roche, or stone brimstone of Marseilles, &c.

The quantity of sulphur, which may be obtained from the galena, or sulphuret of lead, by sublimation, is considerable. Twenty-five per cent is the loss sustained in the reduction of the lead ore, which occurs so abundantly in the neighbourhood of St. Louis. When general, the then lieut. Pike, (_Expeditions, &c. Appendix_) interrogated Mr. Dubuque in 1805, respecting the quantity of lead obtained from those mines, a detailed account of which is given by Schoolcraft, he replied that the mineral would yield seventy-five per cent. of lead, and hence the twenty-five per cent. loss must be the sulphur, together with any foreign matter it may contain.

The experiments of M. Vauquelin, (_Annales de Chimie_, 1811) to determine the quantity of sulphur contained in some metallic sulphurets, show, at once, the proportion which may be obtained from those combinations. Thus he found, that sulphuret of copper contains 21.31 per cent of sulphur; sulphuret of tin, 14.1; sulphuret of lead, 13.77; sulphuret of silver, 12.73; sulphuret of iron, 22; sulphuret of antimony, 25; sulphuret of bismuth, 31.75; sulphuret of manganese, 74.5; and sulphuret of arsenic, 43.

Of native or prismatic sulphur, there are two species, the common and volcanic. The former is of two kinds, the compact and earthy.

Sulphur, says Hanway, (_Travels, &c._) is dug at Baku on the western side of the Caspian sea. It is found in the neighbourhood of the celebrated naphtha springs, some of which form a mouth of 8 or 10 feet diameter.

Von Humboldt (_Annales de Museum National_) communicated to the French national institute, that he discovered, in the province of Quito, a bed composed of sulphur and quartz, in a mountain of mica slate, and also sulphur in primitive porphyry. Kirwan (_Geological Essays_, p. 143) observes, that sulphur promotes decomposition, by absorbing oxygen, while it is thus converted into vitriolic acid; but moisture is also requisite. He attributes, in the same manner, the decomposition of stones that contain pyrites.

As the sulphur, which occurs in commerce, is chiefly obtained from its native combinations, it may be proper to make some brief remarks on this head. Sulphur in the state of combination is abundantly met with, and in all countries. It is found in the state of sulphuric acid, in various salts, as gypsum, epsom salt, native alum, &c.; and united with metals, forming natural sulphurets, as in sulphuret of iron, or iron pyrites, sulphuret of copper, or copper pyrites, sulphuret of lead, or potter's lead ore, called also galena, sulphuret of antimony, or crude antimony, sulphuret of zinc, or blende, sulphuret of mercury, or cinnabar, sulphuret of arsenic, or orpiment, &c. In fact, it appears to be a general mineralizer. It is found also in some plants, and in animal substances.

Without detailing minutely the processes employed for extracting sulphur from its combinations, which may be seen in Thenard, (_Traité de Chimie_, tome i, p. 184) it will be sufficient to observe, that, in general, pyrites, both of iron and copper, are arranged in alternate layers in the form of a pyramid, and the _roasting_ is continued for several months. Part of the sulphur is consumed, and part is sublimed, and is condensed and collected in hollows, in the upper part of the pyramid, whence it is removed several times a day. It is also obtained from pyrites, by a kind of distillation. They are reduced to coarse powder, and put into hollow iron cylinders, or retorts, where the sulphur is disengaged and melted, and thence runs into vessels of water. This process is employed in Saxony, where nine hundred pounds of pyrites will yield one hundred to one hundred and fifty pounds of sulphur, which is afterwards purified.

When melted and cast into wooden moulds, it forms the roll brimstone; and, by sublimation, conducted in large chambers, as we shall afterwards mention, it is converted into the flowers of sulphur. The residue of the sublimation is _sulphur vivum_, which is also used in fire-works. The roll brimstone is frequently adulterated.

In the island of Anglesea, it is obtained by the sublimation of the yellow copper ore. The operation is conducted in kilns, and the sulphur is conveyed by means of long horizontal flues, and collected in large chambers. As the United States furnish an abundance of martial pyrites, and also galena, sulphur might be manufactured in this country, and advantageously, especially from galena, which is very abundant in the neighbourhood of St. Louis. In the roasting of the ore, all the sulphur is now lost, tons of which might be collected.

For the purpose of gunpowder, the purer the sulphur, the better will be the powder; hence attention is always paid to this circumstance. M. Michel, one of the principal refiners of sulphur at Marseilles, has improved the process for purifying sulphur for the purpose of gunpowder. M. Libaw, connected likewise with the French national powder establishment, has furnished a very useful and important memoir on the same subject.

Two methods are proposed for the refining of sulphur, which we will briefly state, namely, fusion, and sublimation. The first is conducted in iron pots fixed in a furnace; and the sulphur, before it is thrown in, is beaten into small pieces with a mallet. This facilitates the fusion, and renders it more uniform. Small portions at a time are thrown into the boiler, and stirred frequently with a wooden spatula. This manipulation ought to be continued till the boiler is filled. The heat must be regulated so as not to inflame, or sublime the sulphur.

The sulphur of commerce is commonly of three different colours, viz: citron-yellow, deep yellow, and brownish-yellow. These colours depend on the different degrees of heat to which the sulphur was exposed, in its extraction. The operation of refining consists in conducting the fire in such a manner, as that the colour of the sulphur will assume a brilliant yellow, bordering on a green. We must, therefore, to produce this effect, operate on the sulphur according to its colour. For the green sulphur, as little heat has been used for its extraction, the fire may be left under the boiler until there is no more left to melt than the top. The sulphur of the yellow colour may be kept longer on the fire, which may be removed when the mass is melted three-fourths. The sulphur of a brown colour, being already much burnt, may be removed when the mass is melted one-half. If it is required to operate on all the varieties at the same time, in order to produce sulphur of a uniform colour, in that case we must fill the boiler one-half with the green sulphur, one-fourth with the yellow, and the remainder with the brown, and removing the fire when the yellow is almost wholly melted. The boiler is then covered with a lid. The fusion is completed by the heat of the mass. The light bodies then raise themselves to the surface, forming a black scum, which is removed, and the heavy bodies fall to the bottom. The boiler remains for four or five hours, uncovering it from time to time to take off the scum. The fluid part is removed, and is suffered to congeal, taking care not to disturb the deposite.

The second process of refining is by sublimation. This operation consists in subliming it in a close apparatus, which in sulphur refineries are boilers placed in brick work, and furnished with heads. These heads communicate by a pipe with a vaulted chamber, placed at some distance from the furnace. The chamber serves to collect the sulphur. There is usually a stone slab fixed between the chamber and the head. The chamber is furnished with one or two iron-plate valves. There is an opening in the head of each boiler, in order to renew the sulphur: it is closed very tight by a plate of iron. There is an opening also in the chamber, to admit a person, which is closed likewise by an iron plate. The heads are luted before the process is commenced.

By this process the sulphur is refined; for the pure part is sublimed, and the foreign substances remain in the pots. The product thus obtained is the ordinary flowers of sulphur. If the heat be moderate, the sublimation is more perfect. It is necessary at the same time that the temperature of the chamber should be low, otherwise the sulphur will melt, which frequently takes place. Coarse particles are separated from the flour, should they occur, by a sieve.

During the first part of the process, there is formed some sulphurous acid gas, which is not produced after the vapour of sulphur forms the atmosphere in the head. This is known to exist, by the acid taste of the sulphur, and its black colour.

Detonation very frequently takes place, and sulphurous acid gas is produced. In the sublimation of brimstone, about ten to eleven per cent. is the usual total loss, of which six or seven per cent. is residue. The acid may be separated from the sulphur by washing it in water, and afterwards drying it. It is then called the washed flowers of sulphur. (See _Traité de l'Art de Fabriquer la Poudre à Canon_, p. 153.) by MM. Bottée and Riffault, for a minute description of this process.

Sulphur undergoes no change by exposure to the air. It is insoluble in water. It breaks in the hand with a crackling noise. At 170 degrees it begins to evaporate, and when collected it is called sublimed, or flowers of sulphur. It melts at 218 degrees. When melted and poured into water, it forms the _sulphurs_ for taking the impression of coin, &c. If melted, and cooled slowly, it will crystallize in the form of needles. It is soluble in different degrees in alcohol, ether, and oils. When sulphur is burnt very slowly in the open air, it unites with oxygen and forms sulphurous acid. This acid is used in bleaching. When mixed with nitre, and burnt in leaden chambers, it forms sulphuric acid, or oil of vitriol, by which process it combines with a larger quantity of oxygen. There is another compound called hyposulphurous acid, all the salts of which are inflammable and burn with a blue flame. Sulphur unites with the alkalies, earths, and metals. If the alkaline sulphurets be dissolved in water, and an acid added, the sulphur will precipitate of a white colour, known by the name of milk of sulphur. It is considered by some a hydrate of sulphur. The same preparation is made by subliming sulphur in a vessel containing the vapour of water. Sulphur unites with chlorine and iodine, forming chlorides, and iodides. With hydrogen, it forms the sulphuretted hydrogen, or hepatic gas, called also the hydrothionic and hydrosulphuric acid; with carbon, the sulphuret of carbon; and with nitre and charcoal, in the state of mixture, it constitutes gunpowder.

The motionless _ignes fatui_ of Italy, which are seen nightly on the same spot, are attributed to the slow combustion of sulphur, emitted through clefts and apertures in the soil of that volcanic country; but the _Will-with-the-Wisp_, which moves in undulations, near the surface of the ground, in swampy situations, and where the putrefactive process is going on, originates in all probability from decaying vegetable and other matters, and the extrication of phosphorus. It is known that the acid of phosphorus is found in plants, and especially those that grow in marshy places, in turf, and several species of the white woods.

_Mealing of Brimstone._ What is termed the mealing of sulphur by fire-workers, is no other than reducing it, if it be the roll, to powder. Large mortars and pestles made of ebony, and other hard wood, and horizontal mills with brass wheels are used. The _mealing table_ is used by artificers. It is generally made of elm, with a rim around its edge four or five inches high. One end is narrow, and furnished with a slider that runs in a groove, and forms part of the rim. After using as much of the powdered brimstone as is required, copper shovels being employed, the rest may be swept out at the slider. This table is also used for the mealing of gunpowder and saltpetre. The muller is generally made of ebony. After reducing it to powder, it is then passed through a lawn sieve, furnished with a cover.

As brimstone is frequently adulterated with different substances, it may be of importance to discover the fraud. We may remark, that, if it is pure, it will be taken up entirely by chlorine gas, or by using a solution of caustic potassa. The latter, however, cannot be depended on in all cases. But the best mode, is that of melting some of it in a ladle; if any residue remains, after the fumes have ceased, the presence of foreign substances may be inferred, for pure sulphur will sublime without leaving any residue. It is not unfrequently adulterated with common flour. There is another mode of determining the quality of sulphur, It should, if pure, be completely soluble in boiling oil of turpentine. If any residue remain, we may infer the presence of foreign substances, either vegetable, earthy, or metallic.

It is obvious, that if the brimstone is impure, the effect of it in fire-works will be imperfect. Flowers of sulphur, however, may be almost always depended on. In all artificial fire, in which sulphur forms a part, the _flame_ is more clear, as the sulphur is pure.

Several modes are recommended for the separation of sulphur from charcoal, in gunpowder, which may be seen by referring to the analysis, or chemical examination of gunpowder.

Sulphur constitutes one of the ingredients, generally speaking, of incendiary compositions, used for military purposes, and, in such cases, is usually mixed with pitch, tar, saltpetre, and sometimes gunpowder. It is said to be one of the substances, which entered into the composition of the ancient and celebrated Greek fire; but the principal character of which, that of burning in water, was owing to the presence of camphor. This substance, associated with sulphur, pitch, and nitre, forms one of the most effective incendiaries of all military fire-works. For such purposes, it is hardly necessary to add, that the common roll brimstone is sufficiently pure.

As to the mode of preparing these works, the custom is to melt the resinous substances first, then to add the sulphur, and finally the saltpetre; and after the whole are melted and thoroughly mixed, to remove the pot from the fire, and add gradually the gunpowder. If a carcass is to be made, tow or hemp, or untwisted rope, is immersed in the composition while hot, and taken out and formed into a ball of the size required. Rope, treated in the same manner, with the same composition, will make a more active tourteaux than the common kind. (See _Carcass and Tourteaux_.)

All oils, whether expressed or essential, can dissolve sulphur. To make this solution, the oil must be poured on the sulphur, and sufficient heat applied to melt the substance. While the oil dissolves the sulphur, it acquires a reddish or brown colour, an acrid, disagreeable taste, and a strong fetid smell, somewhat hepatic, resembling that of oil with sulphuric acid.

_Sec. V. Of Phosphorus._

We mention this substance, because it is used in some experiments, although not in extensive fire-works. It is a very inflammable substance, inflaming either by friction, or an increase of temperature. It produces a most brilliant fire, and when mixed with some substances, exhibits very pleasing phenomena. It usually comes to us in sticks, which must be constantly kept in water to prevent its inflammation. Phosphoric matches, phosphoric fire-bottles, &c. are made of it. These are made in various ways. Phosphorus and sulphur melted together in a small phial, forms the fire-bottle, or some add a portion of lime. A sulphur-match dipped in this mixture and gently rubbed, immediately inflames. They do not last any time, in consequence of the acidification of the phosphorus. Phosphoric tapers are usually made with a glass tube, on the breaking of which, it inflames. When rubbed upon a wall in a dark room, it appears very luminous. Dissolved in ether, and poured upon boiling water in the dark, the vapour as it ascends appears remarkably luminous, and has a pleasing effect. Dissolved in oil, as olive-oil, it forms the phosphorized oil, which may be rubbed on the face and hands without injury. This oil has the same appearance in the dark. The time of night may be known by the light it produces. When mixed with nitrate of silver, sulphuret of antimony, sulphur, chlorate of potassa, &c. and struck with a hammer, it produces an explosion more or less loud. A variety of explosive compounds may be made with it, but they must be used with great care.

When combined with hydrogen, it inflames spontaneously when brought in contact with atmospheric air. It inflames also in chlorine gas. It is supposed to be the cause of the _ignes fatui_, or _Will-with-the-Wisp_. The formation of phosphoretted hydrogen gas may be shown in a variety of ways, as the following: throw some pieces of phosphuret of lime into water, and bubbles of gas will rise, which will take fire on coming to the air; or, put into a flask some phosphorus, iron or zinc filings, water, and sulphuric acid, and the gas will be generated; or, introduce into a small retort, a solution of potassa, and a piece or two of phosphorus, and apply heat, immersing the beak of the retort in a basin of water, the gas will pass over, and inflame as it comes to the surface of the water. In all these experiments, the water is decomposed; its oxygen goes to a part of the phosphorus in the first experiment, and the hydrogen of the water then unites with another portion of phosphorus, which is then evolved; in the second experiment, the oxygen oxidizes the metal, and the hydrogen dissolves a part of the phosphorus; and in the third experiment, the phosphorus unites with the potassa, forming a phosphuret, which decomposes the water, the hydrogen of which passes off in combination with some of the phosphorus, forming the phosphuretted hydrogen gas.

The cause of the spontaneous combustion is, that the oxygen of the atmosphere unites with the hydrogen and the phosphorus, and forms water and phosphoric acid; the latter producing a beautiful corona as it rises in the air. The heat and light given out proceeds as well from the oxygen gas, as from the phosphuretted hydrogen gas. When saturated with oxygen, it is no longer inflammable.

There are some other experiments which can be made with this singular substance.

It was formerly obtained from urine, as that fluid contains some phosphoric salts. It is now prepared from bones. These are burnt to an ash, and diluted sulphuric acid is poured on it; the phosphoric acid it contains is then disengaged, and remains in the fluid. The sulphate of lime is then separated, the fluid boiled to dryness, and the dry mass is mixed with charcoal, and distilled in the open fire.

The phosphoric pencil, for writing on a wall, paper, &c. to be luminous in the dark, is nothing more than a bit of phosphorus put into a quill. It must be kept in water, and when used, frequently dipped in water, to prevent its taking fire.

The _phosphoric_ stone of M. Bucholz, described in the _Archives des Découvertes_, ii, p. 109, is a phosphuret of magnesia, prepared by melting thirty grains of phosphorus in a small flask, and adding twenty or thirty grains of calcined magnesia. Although this process is given by Bucholz, yet, as it is difficult to prevent the inflammation of the phosphorus, the best mode would be to bring the vapour of phosphorus in contact with magnesia, in the same manner as in preparing phosphuret of lime.

The pyrophorus of Wurzer is nothing than a phosphuret of lime. It is prepared by taking two parts of pulverized quicklime, and one part of phosphorus; introducing them into a bottle, and covering it with three parts of quicklime, leaving one-third of the bottle empty; then putting the bottle into a crucible surrounded with sand, previously stopping the mouth with clay, and applying heat. Remove the phial when the phosphorus appears to sublime of a red colour. When the bottle is opened it becomes luminous, and brought out it inflames.

Phosphorus in the state of acidification, and united with lime, is found in abundance. Whole mountains in the province of Estremadura in Spain, are said to be composed of this combination. According to Mr. Bowles, this stone is whitish and tasteless, and affords a blue flame without smell when thrown upon burning coals. Mr. Proust observes, that it is a dense stone, not hard enough to strike fire with steel, and is found in strata, which always lie horizontally upon quartz, and which are intersected with veins of quartz. He adds, that it does not decrepitate on burning coals, but burns with a beautiful green light. This stone is the common phosphorite. It contains, according to Klaproth, 32.25 per cent. of phosphoric acid.

Several substances are known under the name of phosphorus, although they do not contain it, such as Baldwin's phosphorus, or ignited muriate of lime, Canton's phosphorus, or oyster-shells calcined with lime, and Bologna phosphorus, or calcined sulphate of barytes.

_Sec. VI. Of Charcoal._

Charcoal performs an important part in all the various kinds of fire-works. The facility with which it decomposes nitric acid, when it is combined with salifiable bases, as with potassa in saltpetre, and its action in all cases wherein nitre is concerned, are sufficient examples of its effect.

Pure carbon is the diamond. It affords by combustion in oxygen gas, the same gas as common charcoal, when charcoal is burnt in oxygen, or in atmospheric air. This gas is carbonic acid, or fixed air. Charcoal has been considered a long time an oxide of carbon, and according to some, as Berthollet, a compound of carbon, hydrogen, and oxygen.

Charcoal is insoluble in water. It is not affected by the most violent heat, if confined in close vessels. It is an excellent conductor of electricity, but a bad conductor of heat. It is very indestructible; and, therefore, when wood is charred, it will remain a long time under ground without rotting. As an antiseptic, it is powerful. It will therefore prevent the putrefaction of bodies, and even recover tainted meat. As a preservative of water, for sea-voyages, it has been long known. The charring of water casks is designed for the same purpose. The quality of wine is said to be improved by having the casks previously charred. It possesses the property of absorbing gases, and to this property is ascribed its use as an antiseptic, and its disinfecting quality. To the distiller it is useful, as it destroys effectually the burnt or empyreumatic smell of liquor. When heated to eight hundred degrees in the open air, it burns. In oxygen gas the combustion is brilliant, forming in both instances carbonic acid gas, called also aerial acid, fixed air, mephitic air, and calcareous acid. This acid is formed in a variety of processes, and is carbon saturated with oxygen.

Carbon exists in various states of combination, and many of the compounds into which it enters are inflammable; hence carbonic acid is generated in the combustion of coal, oils, fat, &c. In the form of an acid, it is abundant in various stones, such as the calcareous carbonates, as chalk, marble, limestone, and calcareous spar, barolite, &c. all which effervesce with acids, the carbonic acid being liberated. When limestone is burnt, to obtain quicklime, the carbonic acid is disengaged, for the presence of this acid distinguishes limestone from pure lime. Carbonic acid is generated in various processes of nature as well as art. Hence it is produced in the respiration of animals, and is found in a gaseous state in wells, cellars, caverns, &c. It neither supports animal life, nor combustion. In mines it is called choke damp; and the Grotto del Cani, in the kingdom of Naples, has been long celebrated, on account of it. This cave is in the side of a mountain, near the lake Agnano, measuring not more than eighteen feet from its entrance to the inner extremity; where if a dog or other animal that holds down its head be thrust, it is killed by the gas. Some experiments were made in this cave with gunpowder, which see. Carbonic acid, during the formation of alcohol, in the vinous fermentation, is generated, and its production appears to be designed by nature to carry off the excess of carbon, which gives rise to that phenomenon called fermentation. When combined with water, it forms aerated water, and with alkalies and water, the aerated alkaline waters. Its union with bases forms salts called carbonates. Plants have the property of decomposing it, and in this respect nature has employed a mean of regenerating the atmosphere, on the purity of which depends, in an eminent degree, the very existence of animal life. The prime equivalent of carbonic acid is 2.75, and carbonic acid is composed of carbon 0.75 + 2.0 oxygen.

Carbonic acid may be decomposed when combined with a base, as lime, by phosphorus and heat, for charcoal and a phosphate of lime will be produced. But carbonic acid in the state of gas may be decomposed by potassium. Five grains of potassium will decompose three cubic inches of gas, and be converted into potassa, producing at the same time three-eighths of a grain of charcoal. If passed over a coil of fine iron wire heated to redness, in a porcelain tube, and the operation repeated, the iron will be oxidized, and the carbonic acid changed into carbonic oxide gas.

Charcoal will not burn in dry chlorine. It unites with a less proportion of oxygen, and forms carbonic oxide gas, which burns with a deep blue flame. This combination is formed by distilling in a red heat, a mixture of equal parts of iron filings and chalk. This gas mixed with chlorine gas, and exposed to the sun's rays, will unite with it, and form chlorocarbonic acid gas. Carbon unites with azote, and forms cyanogen, the base of Prussic acid. It unites likewise with hydrogen in two proportions, forming the hydroguret and the bihydroguret of carbon, both of which are carburetted hydrogen gases. The former is obtained by distilling a mixture of four parts of sulphuric acid, and one of alcohol. The gas is very inflammable, and burns with great splendour; and on that account may be used for exhibition, in an apparatus similar to that of Cartwright. (See _Fire-works with Inflammable air_.) It was called by the German chemists olefiant gas. The other species, called also the light carburetted hydrogen gas, may be obtained by agitating the mud at the bottom of stagnant pools; and by the distillation of moist charcoal, wood, pitcoal, pitch, or almost any animal or vegetable substance. The gas, used for _gas-lights_, is the same. It is usually obtained from pit coal. We may merely observe, that the gas used for that purpose, _i. e._ for illuminating streets, theatres, manufactures, &c. as obtained in the common method, is not altogether the bihydroguret of carbon; but, according to the experiments of Dr. Henry, a mixture of that gas with the hydroguret, and occasionally carbonic oxide.

Carbon enters into other combinations. It exists as a component part of gums, resins, sugar-starch, and other vegetable products, as the vegetable acids, its union with iron forms steel, a substance greatly used in the preparation of some fire-works, especially in some of the _rains_ and _stars_, and in the composition of _brilliant fire_. (See _Iron_.)

As charcoal enters into the composition of gunpowder, and the effective force of powder depends considerably on the quality, as well as the proportion of charcoal, it is obvious for this purpose, it should be as pure as possible.

Carbon is always obtained from some of its combinations, as from pitch, tar, rosin, wood, and oil. Various processes are employed for this purpose. Thus, by the combustion of rosin and oil, as well as pitch, tar, turpentine, &c. a soot is formed that collects, called lampblack, which is nothing more than the carbon or charcoal. When pit-coal is _charred_ in an oven, called a coke oven, all the bitumen and sulphur contained in it are disengaged, and a charcoal remains, called, however, _coke_. Wood, when charred is decomposed; all the volatile parts are disengaged with carburetted hydrogen gas, and the woody fibre is converted into coal. This coal is more or less dense according to the compactness of the wood. Hard woods furnish the most solid coal, and light woods on the contrary.

When the solid parts of animals, as bone, are charred, the volatile products, principally ammonia or volatile alkali, are dissipated, and there remains a substance called bone-black, improperly called, _ivory black_.

The carbonization of wood in the common way is well known: after it is cut to the lengths required, it is piled on the ground in a pyramidal form, and covered with sod and clay, leaving a place for the current of air, and the smoke. The wood is then set on fire, and when the whole is burnt to a coal the vents, &c. are closed with sod and clay.

Nicholson (_Chemical Dictionary_) observes, that in the forest of Benon, near Rochelle, great attention is paid to the manufacture, so that the charcoal made there fetches twenty-five or thirty per cent. more than any other. The wood is that of the black oak. It is taken from ten to fifteen years old, the trunk as well as the branches, cut into billets about four feet long, and not split. The largest pieces, however, seldom exceed six or seven inches in diameter. The end that rests on the ground is cut a little sloping, so as to touch it merely with an edge, and they are piled nearly upright, but never in more than one story. The wood is covered all over about four inches thick with dry grass or fern, before it is enclosed in the usual manner with clay; and when the wood is charred, half a barrel of water is thrown over the pile, and earth to the thickness of five or six inches is thrown on, after which it is left four-and-twenty hours to cool. The wood is always used in the year in which it is cut.

Turf or peat has been charred lately in France, it is said, by a peculiar process, and, according to the account given in Sonnini's Journal, is superior to wood for this purpose. Charcoal of turf kindles slower than that of wood, but emits more flame, and burns longer. It boiled a given quantity of water four times, while an equal weight of wood charcoal boiled the same quantity but once. In a goldsmith's furnace, it fused eleven ounces of gold in eight minutes, while wood charcoal required sixteen. The malleability of the gold, too, was preserved in the former instance, but not in the latter. Iron heated red-hot by it, in a forge, was rendered more malleable.

In charring wood it has been conjectured, that a portion of it is sometimes converted into a pyrophorus, and that the explosions that happen in powder-mills are sometimes owing to this.

Bartholdi supposes, that such explosions are owing to the formation of phosphoretted hydrogen gas, while others attribute them to the absorption of oxygen, by the hydrogen contained in the coal, and the consequent evolution of free caloric. Percussion, which necessarily takes place in mixing the materials of gunpowder by stampers, no doubt accelerates the combustion. The addition of water, and having the charcoal previously pulverized, will prevent such accidents. (See _Gunpowder_.)