J. Bodington of London, invented a machine to try the force of gunpowder. M. the chevalier d'Arcys made an eprouvette on the principle of Mr. Robins. M. Le Roy proposed to employ the different elastic forces of inflammable air, but his method has never been used. M. Tresnel also proposed an eprouvette, which was announced in the French journal, entitled Nouvelles de la République des Lettres et des Arts, par M. de la Blancherie, for 1782, p. 190.
It is hardly necessary to observe, that the eprouvette has undergone some improvements: thus, the eprouvette of Darcy consists of a cannon suspended at the extremity of a bar of iron, and the graduated arc measures the recoil; the eprouvette of Regnier is nearly the same, and the arc determines the force of the powder.
A description of mortar-eprouvettes generally, may be seen in the work of MM. Bottée et Riffault, (Traité sur l'art de Fabriquer la poudre à canon,) and in the Memoirs of Proust (Journal de Physique, tome lxx, et suiv.), &c.
I saw a model of an improved eprouvette, which appeared to possess every advantage, at the Ordnance Arsenal near Albany; an index hand moved in an arc.
Quicklime is said to increase the force of powder. Dr. Baine says, that three ounces of pulverized quicklime being added to one pound of gunpowder, its force will be augmented one-third; shake the whole together, till the white colour of the lime disappears.
The preservation of gunpowder in properly constructed magazines, of which we will have occasion to speak hereafter, is a subject that should claim our attention. The greatest difficulty, if any, exists at sea, and on this head we have a variety of opinions.
Mr. James (Military Dictionary, p. 348) says, that it has been recommended to preserve gunpowder at sea by means of boxes lined with sheet-lead. M. D. Gentien, a naval officer, tried the experiment by lodging a quantity of gunpowder and parchment cartridges in a quarter of the ship which was sheathed in this manner. After they had been stowed for a considerable time, the gunpowder and cartridges were found to have suffered little from the moisture; whilst the same quantity, when lodged in wooden cases, became nearly half destroyed.
It has been recommended to line powder magazines with lead, as a mean for preserving the powder from dampness. The lead, it seems, so far attracts moisture, as to condense it. In the last volume of the Transactions of the American Philosophical Society, is a memoir on leaden cartridges, by Wm. Jones, Esq. the late secretary of the navy, which, besides preserving the powder, has advantages over either paper or flannel. See [Magazine.]
What is termed the analysis of gunpowder, is nothing more than the separation of its component parts, and determining the relative proportions of its respective ingredients. We may indeed examine the quality of the nitrate of potassa, by dissolving a portion of powder in distilled water, and employing the reagents mentioned under the head of nitre; but for the purpose of separating, as well as determining the proportion of saline matter, charcoal and sulphur, it may be readily accomplished in the following manner: Take a given quantity of gunpowder and affuse it in distilled water sufficient to dissolve the salt; after suffering it to remain for some time, applying heat to assist the solution, decant the whole upon a filter of unsized paper. The saltpetre and other saline matter will pass through, and the sulphur and charcoal remain on the filter. By evaporating the solution to dryness, and weighing it, the quantity of saltpetre will be found; or, after drying the mass on the filter, and weighing it, by subtracting its weight from that of the original, it will give the loss sustained, which of course is the saltpetre. By exposing the mass to a heat sufficient to evaporate the sulphur, it will be expelled; the loss sustained will indicate its quantity, and the weight of the residue the proportion of charcoal. The sulphur may be even separated by subjecting gunpowder itself to the action of a well regulated heat; it will sublime, and leave the nitre and charcoal. It takes a much higher temperature to inflame gunpowder than is required to volatilize sulphur. The method of extracting the nitre from damaged powder, we have already noticed. See [nitre.] This process also depends on the solubility of the nitre, and the insolubility of the charcoal and sulphur. Bishop Watson, in his Chemical Essays, proposed the examination of gunpowder by solution and sublimation; a process sufficiently accurate. If it should be our object to ascertain the presence and quantity of foreign substances, in the saltpetre, this may be accomplished by following the process already given, viz: by collecting the precipitates, &c. determining their weights, and making the necessary allowance, for the new compounds, as the carbonates of lime, sulphate of barytes, muriate of silver, and the like.
Baumé proposed the analysis of powder by sublimation, in order to separate the sulphur, using however a graduated heat. Another mode consists in distilling the powder in a retort with water, and collecting the sulphur and sulphuretted hydrogen gas, and then separating the charcoal, &c. A third process was recommended by Pelletier, after the separation of the nitre, by subliming a mixture of the residue with mercury, which, however, presents no advantages. The use of nitric acid has also been recommended, in order to acidify the sulphur. For this purpose nitric acid is poured on the residue, and the whole is digested for some time, renewing the acid as it is decomposed. By this means the carbon, as well as the sulphur, is acidified, and carbonic acid gas with deutoxide of azote are disengaged, leaving the sulphuric acid formed by the union of oxygen with the sulphur, in the remaining fluid, from which it is separated by nitrate of barytes, and its quantity ascertained by the sulphate of barytes produced. The proportion of sulphur, in the sulphuric acid, is then calculated.