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.
The following proportions are now used in France, for the manufacture of gunpowder for war, for hunting, and for mining.
| For war. | For the chase. | For mining. | |
| Saltpetre, | 75.0 | 78 | 65. |
| Charcoal, | 12.5 | 12 | 15. |
| Sulphur, | 12.5 | 10 | 20. |
After having made choice of the materials, the nitre being pulverized, is passed through a brass sieve; the sulphur is pulverized by means of a muller, or other contrivance, and also sifted in a bolter; the quantities are then weighed, as well as the charcoal.
The mixing of these substances is performed in a series of mortars, hollowed out of a strong piece of oak wood; and by the aid of pestles or stampers, which are set in motion by machinery and water power, the mixture is thoroughly made. The end of the stampers is usually covered with, and sometimes made of, brass, and the mortars are also, in some powder mills, lined with brass. The mill has generally two rows of mortars and stampers, of ten each. The nitre, sulphur, and charcoal, in proper proportions, are put into each mortar. The charcoal is first introduced into the mortar, being sometimes previously pulverized; then wetted with water, and the pounding is continued for thirty minutes. The nitre and the sulphur are then added, and the whole is stirred with the hand. More water is then added; it is again stirred, and the operation of pounding is continued. The object of adding the water is to prevent the so called volatilization of the ingredients, and to give the mixture the consistency of paste, and at the same time to prevent the explosion of the powder; a circumstance, which must be always guarded against.
After the operation is continued for half an hour, the pounders are stopt, and the powder is then re-exchanged by means of copper or brass ladles; that is to say, the powder of the first mortar is removed, and put into a box, and the contents of the second mortar are put into the first, that of the third is put into the second, that of the fourth into the third, &c. in succession, and in the last, the contents of the first mortar.
We make, in this manner, twelve exchanges, allowing one hour between two, and adding water from time to time, to the mixture, and especially during the summer months. After this, the pounders are again set in motion, for the space of two hours, and the operation is finished. Fourteen hours are generally required to complete the mixture, which is then in the form of paste. It is then granulated. After being partially dried, the graining is performed by passing it through sieves, which are more generally formed of parchment. These sieves are made to work horizontally, and the powder is caught in vessels placed beneath. The size of the grain depends on the sieve; hence, fine grain, or coarse grain powder is thus obtained. In the sieve is usually placed a contrivance to break the masses, and to cause the powder to pass through in grains. After this, the powder is again passed through a second sieve, commonly called a grainer, the holes of which are of the same diameter as the powder we wish to obtain. It is then put into another sieve, which permits only the dust to pass, whilst the grain-powder remains. As the powder, however, contains some grains too large, as well as others too small, we may separate the former by a fourth sieve, of a suitable size. The dust and fine grain are carried to the mill, and worked over. The powder for war, and for mining, is dried immediately after the graining.
Formerly, the powder was dried in the open air, by spreading it on tables lined with cloth, or in oblong boxes; but serious inconveniences resulted from it, and, particularly, the powdermakers were obliged to watch the temperature, as well as the state of the atmosphere. When the latter was moist, the drying was suspended.
M. Champy, however, has obviated these inconveniences by a very advantageous process, which consists in raising the temperature of the air to 50 or 60 degrees, and causing it to pass from the chamber in which it is heated, through cloths, on which is spread a bed of powder, of a certain thickness. By this means, large quantities of powder may be dried, in all seasons of the year, in a short time, and at little expense. In whatever manner the drying is performed, there is always more or less dust formed, which, to make the grain of one uniform appearance, must be separated by a hair sieve. This operation is called the dusting.
Whether we adopt the plan recommended by M. Champy, or heat the rooms for the drying of powder to a certain temperature, by means of steam pipes, a plan which presents every advantage, or use the old mode, the effect is the same.
The musket, or hunting powder, undergoes an operation more than the powder for war, namely, that of glazing, which is performed before it is dried. With the exception of this process, it is made in the same manner, using, however, a finer sieve in granulating it. The glazing has for its object the smoothing, or removing the asperities of the grain, and to prevent its falling into dust, and soiling the hands.
The powder intended for glazing is first exposed an hour to the sun on one cloth, in winter, and between two cloths in summer, in order to dry it more perfectly, which is very necessary before the operation of glazing. For this purpose, it is put into a vessel like a barrel, which is turned horizontally upon its axis, by machinery. This barrel is furnished with bars that go across, intended to augment the friction, or rubbing of the grain, and expedite the process. The barrels are made to turn slowly, to avoid breaking the grain, and at the expiration of eight or twelve hours, the glazing is finished, the powder having acquired a sufficient hardness and polish. After removing the powder, the dust is separated in the usual manner.
Gunpowder-mills are mills, in which powder is prepared, by pounding and beating together the ingredients of which it is composed. They are always worked by water-power, and as there are generally many of them belonging to the same manufactory, one dam of water will furnish a sufficient supply. In the construction of powder-mills, the frame of the house is made very stout, and the roof put on lightly, so that in case of explosion, it may be carried off easily, and thus give vent to the powder, without much injury to the works. The lights, to enable the work to be carried on at night, are placed on the outside of the building, beyond the reach of the powder, and by means of glass windows, the light passes into the mill. It is lamentable, indeed, that so many accidents occur in the operation of making powder. This may take place, as it has to our knowledge, by the friction of the pounders. Their weight, the rapid succession of the blows, and the dryness of the powder, are the principal causes of such accidents, and sometimes by the inattention of the workmen, suffering nails, and the like, to get among the materials. I once witnessed the effect of an explosion of the kind, in the neighbourhood of Frankford, in the vicinity of Philadelphia, at the old and well-known powder mills, at that place. It was produced, in consequence of the friction, by the neglect of the men not adding water at a proper time, to keep the materials moist. The mill in which the explosion took place was not much injured; but the roof, together with the men, were sent a considerable distance. Some of the latter fell into the mill-race, and were much injured. The effect, however, did not stop here; for the fire communicated, strange as it may appear, to some of the other mills, although at some distance, and blew them up. Several explosions have happened at the same mills.
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