Second method.
Second method.—There is another method of preserving filings so as to keep two or three months in winter, which is done by rubbing them between strong brown paper, which has been previously moistened with linseed oil. In heating the brimstone the caution given in Article 3, must be observed in the event of its catching fire.
We must observe in fine on this article, that it will be well to anticipate a little trouble in the preparation of this granulated Iron-sand, for cast-iron being of so hard a nature as not to be cut by a file, we are obliged to pulverize it, or reduce it to grains by the method we have described, which is rather difficult to perform; but when we consider what beautiful sparks this iron yields, no pains should be spared to granulate such an essential material.
We must further observe, that when these plates of iron cannot be procured, an old cast-iron pot may be employed; but especial care must be taken that its surface be perfectly free from rust and other impurities previous to its being pulverized, otherwise it will entirely destroy the effect it is intended to produce.
It is to the Chinese we are indebted for this method of rendering fire so brilliant and variegated in its colours, who discovered it long before Father d’Incarville made it known to the European countries. This sand, when it inflames, emits a light exceedingly vivid; and it is surprising to see fragments of this matter not larger than a poppy seed, form all of a sudden luminous flowers of stars, twelve and fifteen lines in diameter. These flowers are also of different forms, according to that of the inflamed grain, and even of different colours, according to the matters with which the grains are mixed. But rockets, into which this composition enters, cannot be long preserved, unless prepared as described in the early part of this article.
There are many other substances occasionally employed in the composition of fire-works, but as they can be procured at all Chemists and Druggists ready for the purpose, we consider it unnecessary to give any detail respecting them, further than enumeration. They are chiefly the following, viz. Camphor, which is used to improve the appearance of the fire; Antimony, or Sulphuret of Antimony, Sal-ammoniac, Verdigrease, and Pitch, for giving to the fire different and particular shades of colour; Flowers of Benjamin, or Benzoic-acid, for imparting to it an agreeable odour; and Spirits of Wine, or Camphorated Spirits, for mixing up the ingredients into a paste. These liquids are found to answer much better than common water, or gum-water, which is sometimes used, as they do not dissolve the salt-petre, and are therefore not so liable to produce a separation of the materials employed. Lamp-black is sometimes used instead of charcoal, and is supposed to have the effect of diminishing the heat of the fire, while it does not materially lessen its brilliancy. Thence it is a considerable ingredient in what is called cold-fire, the seeming paradox of which we shall hereafter reconcile. For the same purpose, that of diminishing the force of the composition, powdered glass and saw-dust have been frequently employed; but probably these effects might be better, and with more certainty answered, by lessening the proportion of nitre.