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