The intimate mixture, therefore, and the determinate proportions of saltpetre, charcoal, and sulphur, form gunpowder; the different qualities of which, depend, as well upon the proportions which are used, as on the purity of the materials, and the accuracy with which they are mixed.
Gunpowder is reckoned to explode at about 600° Fahr; but, if heated to a degree just below that of faint redness, the sulphur will mostly burn off, leaving the nitre and charcoal unaltered.
The saltpetre should be perfectly refined, and entirely free from deliquescent salts; the sulphur as pure as possible, and, for that reason, a preference should be given, to that which is sublimed, or distilled; and the charcoal should be prepared in iron cylinders, as described under that head, from woods, which are light and tender, as the linden, willow, hazle, dogwood, etc.
There is a considerable difference in the proportions used by different nations; but, from the many accurate and conclusive experiments of the French chemists, their formula is certainly the most perfect. In English powder, three-quarters of the composition are nitre, and the other quarter is made up of equal parts of charcoal and sulphur; but sometimes, to seventy-five parts of nitre, fifteen of charcoal is used, adding ten of sulphur. Their government powder is the same for cannon, as for small-arms.
According to a number of experiments, made at Grenille, it was found, that the proportion of saltpetre in gunpowder, must be in a given ratio with the charcoal, so that the latter might effectually decompose it in the act of combustion; and hence the ratio is as 12 of the latter to 75 of the former, and these, with 12 of sulphur, are the proportions generally employed. Ruggeri (Pyrotechnie Militaire, p. 91,) gives, as the proportions, 12 parts of saltpetre of the third boiling, 2 parts of charcoal, and 1 part of sulphur. The proportions, used in Sweden, are 75 saltpetre, 9 sulphur, and 16 charcoal; in Poland, 80 saltpetre, 8 sulphur, and 12 charcoal; in Italy, 76 saltpetre, 12 sulphur, and 12 charcoal; in Russia, 70 saltpetre, 11 sulphur, and 181/2 charcoal; in Denmark, 80 saltpetre, 10 sulphur, and 10 charcoal; in Holland, 76 saltpetre, 12 sulphur, and 12 charcoal; in Prussia and Austria, 78 saltpetre, 11 sulphur, and 11 charcoal; and in Spain, 77 saltpetre, 111/2 sulphur, and 111/2 charcoal.
According to Klaproth and Wolff, (Dictionnaire de Chimie, translated into French by MM. Lagrange and Vogel), Berlin powder is composed of three-quarters nitre; one-eighth sulphur, and one-eighth charcoal; Chinese powder, of 16 parts nitre, 6 charcoal, and 4 sulphur; Swedish powder, of 75 parts nitre, 16 sulphur, and 9 charcoal; the powder of Lissa, of 80 nitre, 12 sulphur, and 8 charcoal; and English powder, on the authority of Beckman, as follows: Powder for war, 100 parts of nitre, 25 charcoal, and 25 sulphur; musket powder, 100 nitre, 18 sulphur, and 20 charcoal; pistol powder, 100 nitre, 23 sulphur, and 15 charcoal; strong cannon powder, 100 nitre, 20 sulphur, and 24 charcoal; strong musket powder, 100 nitre, 15 sulphur, and 18 charcoal; and strong pistol powder, 100 nitre, 10 sulphur, and 18 charcoal. German powder, for war, is composed, generally, of 0.70 saltpetre, 0.16 charcoal, and 0.14 sulphur. A small portion of gum is sometimes added, to make the grain firmer; but such additions retard the combustion, and the effect.
The addition of gum arabic, however small, must injure the quality of gunpowder, although it has the effect of making the grain firmer, and less liable to fall into meal powder. The grain is also made heavier, and less liable to absorb moisture. M. Proust, in his second memoir on gunpowder, mentions the use of icthyocolla, a fish glue, for the same purpose; and, nevertheless, speaks of some advantages that the gunpowder, prepared with it, possesses.
It is observed by Mr. Coleman, of the Royal Powder Mills of Waltham abbey, that it is not exactly ascertained, whether there is any one proportion, which ought always to be adhered to, and for every purpose. We have no hesitation in believing, for our own part, that the French formula is the most correct, from the numerous experiments made at the royal manufactory at Essone, near Paris.
A very considerable variation is found in the proportions of the ingredients of the powder of different nations and different manufactories. The powder made in England, is the same for cannon as for small arms, the difference being only in the size of the grains; but in France, it appears, that there were formerly six different sorts manufactured; namely, the strong and the weak cannon powder, the strong and the weak musquet powder, and the strong and the weak pistol powder. The following are the proportions in each, though the reason of this nicety of distinction is not very obvious. For the strong cannon powder, the nitre, sulphur, and charcoal were in the proportions of 100 of the first, 25 of the second, and 25 of the third: for the weak cannon powder, 100, 20, and 24: for the strong musket powder, 100, 18, and 20; for the weak, 100, 15, and 18: for the strong pistol powder, 100, 12, and 15; for the weak, 100, 10, and 18.
The Chinese powder appears, by the analysis of Mr. Napier, to be nearly in the proportions of 100 of nitre, 18 of charcoal, and 11 of sulphur. This powder, which was procured from Canton, was large-grained, not very strong, but hard, well coloured, and in very good preservation.