A Manual of Pyrotechny; or, A Familiar System of Recreative Fire-works

by G. W. Mortimer

[SECTION II.]
Materials.

Having in the preceding Section, entered somewhat largely on the nature and properties of Gunpowder, and consequently of the ingredients which compose it, any further observations on them would be unnecessary, providing the ingredients and proportions always remained the same. But as the ingredients used in the manufacture of that article are frequently employed in various other proportions, to form compositions for filling fire-works, it is necessary to give some further directions for the choice and purification of these articles, which, together with the apparatus made use of in the making of fire-works, will form the subject of the present section.

Nitre.

1. Nitre.—Among the various articles made use of in the composition, none are of greater importance than salt-petre, for on the quantity and purity of this depends all the force and much of the brilliancy of the fire. The most common sort is that usually sold by the grocers, and is generally in large lumps formed of an assemblage of small crystals somewhat transparent, and often mixed with earthy matter and many other impurities. In its purest state it is in the form of small six-sided prismatic crystals, not apt to grow moist or powdery on exposure to the air. The pure nitre is now become very expensive, so it is of consequence to know how the common nitre, or nitre of commerce may be purified, for it is found to answer no purpose in Pyrotechny unless such change or purification in it have been effected.

Nitre is found, (like most of other saline bodies) to be much more soluble in boiling water, than in water of the ordinary temperature. If therefore the nitre of commerce be dissolved in a small quantity of boiling water, and the solution be properly strained, the liquor, when cold, will afford crystals that are very pure. The following is the most convenient method of proceeding: dissolve the nitre in boiling water, (which should be soft water,) in the proportion of about a quart to each pound of nitre; and that the solution may be more easily effected, let the nitre be reduced to a powder, previous to its being immersed, and let the vessel containing the nitre and water be kept at the boiling heat till all the salt is dissolved; then strain the liquor, while hot, through thick blotting paper, placed in a clean funnel; and set by the filtered liquor in a shallow vessel, in a cold place, to crystallize. The crystals thus obtained are to be dried, first in blotting-paper, and then before the fire, and kept for use. From the remaining solution, which is sometimes called mother-water, fresh crystals may be procured by boiling it in a clean tin vessel till a filming scum arises to the surface, then filtering it through paper, and setting it aside to crystallize as before.

Very pure nitre may also be obtained from damaged gunpowder, which may be sometimes procured at a cheap rate, at the shops where it is sold for this purpose. The damaged powder must be ground with a small quantity of hot water, in a large wooden or stone mortar, otherwise it may be boiled over a gentle fire, with as much water as will cover it, till as much as possible of the nitre is dissolved; the liquor is then to be strained through a thick flannel bag, afterwards filtered through blotting-paper while hot, the sediment to be boiled down till a film rises on the surface; again filtered and set by to cool and crystallize, as directed in the process for the former method.

As the nitre must always be reduced to fine powder, previous to mixing it with other substances, this is easily done by dissolving it in a little more than its own weight of boiling water, keeping the solution over a gentle fire, and continually stirring it with a flat stick till all the water is evaporated, when the powder is to be taken out and dried before a gentle fire; during which, care must be taken not to let it remain too long, or exposed to too great a heat, otherwise it will be melted into a firm cake. The drying may be completed by suffering it to remain a sufficient time on paper before the fire. For the purification of salt-petre, both these methods may (by attending to the foregoing instructions,) be practised with success; but of the two, we would more strongly recommend the former.

Sulphur.

2. Sulphur.—Sulphur is the next ingredient, in regard to importance, as being the most inflammable material we are acquainted with. It exists in three states, in all of which it is occasionally employed in fire-works; the first is that brought from the neighbourhood of volcanoes, and is called native sulphur, but more commonly sulphur vivum, though (it may be observed,) what is sold in the shops under this name is a drossy powder, the refuse left after purification. The second is that in the roll, called roll sulphur, or stone brimstone. The third is the sublimed sulphur, or as it is commonly called flower of sulphur; this when genuine is the purest, and is found to answer best for all nice and delicate articles, and from its being already in a state of powder it is by far the most convenient, as the others require to be ground or mealed previous to their being used. The first kind is the cheapest, and answers pretty well for all large and coarse articles, but as it is most frequently mixed with earthy matter and other impurities, the use of it we would not very much recommend. The second is found to be the strongest, and which is mostly used, particularly for most of the ordinary articles; but such is the desire of gain, that this article of sulphur is not suffered to pass through the hands of dealers without its quality being reduced by adulteration, which they effect by mixing with it rosin, flour, &c.; when pure it is of a bright yellow colour, dense but not too heavy, easily cracks with the heat of the hand, and the broken parts look bright and crystallized. There is another kind of sulphur (though not generally known among dealers) which does not burn like the others, and what is rather singular, it emits no sulphurous smell, for being put upon the fire it melts just like common wax; this sort is found in great abundance in Iceland near Mount Hecla, and Carniola. This sulphur is commonly of a reddish colour, like that found in the straits of Heildesheim, where it is likewise of several colours, as pale yellow and green, and generally adheres to the surface of stone and rocks, from which it may be easily broken off and collected; that which is perfectly yellow of each kind is the best. That of our first description, or sulphur vivum, is sometimes called quick sulphur from its undergoing no change by fire, since its productions by nature; and in some countries it is called virgin sulphur, because the women and girls in Campania frequently make a kind of paint of it, for no less delicate purpose than that of beautifying the face. Should either kind be met with in an impure state the following method may be applied for the purpose of purification.