The following substances are in requisition by the Pyrotechnist:—
Zinc. This metal is employed in the form of fine powder, which is obtained as follows:—The metal, scarcely melted, is poured into a hot mortar, where it is reduced to powder, being kept during the operation at a temperature of 401° F. It is then sifted to remove any particles which may have escaped contact with the pestle.
Copper. This metal may be obtained in a state of minute division by precipitating it from a solution of sulphate of copper by means of iron, the precaution being taken of using a large quantity of iron. The precipitate, after being well washed, is dried between folds of blotting paper, and kept in well stoppered bottles.
Iron-sand. A quantity of sulphur is melted in a crucible over a slow fire, and when it is quite fluid, iron filings are thrown in while the whole is being stirred. The crucible is removed from the fire, and the contents are rapidly stirred until cold. The material is then rolled on a board till it is broken up as
fine as corned powder, after which the sulphur is sifted out.
Soda Powder. This powder is prepared with the same precaution as ordinary gunpowder, the proportions which answer best being:
| Nitrate of soda | 630 | parts. |
| Sulphur | 125 | ” |
| Charcoal | 125 | ” |
| —— | ||
| 880 | parts. |
As the nitrate of soda is hygrometric, this powder must be preserved in closed vessels from the moisture of the air.
Lead Powder. This mixture is also prepared like gunpowder, and the constituents are used in the following proportions:
| Nitrate of lead | 12 | parts. |
| Nitrate of potash | 2 | ” |
| Charcoal | 3 | ” |
| — | ||
| 17 | parts. |