Composition of Bengal Lights.
| Saltpetre, | 3 | lbs. | |
| Sulphur, | 13 | oz. | 4 dr. |
| Antimony, | 7 | oz. | 4 dr. |
They are pulverized and mixed in the usual manner, and passed three times through a hair sieve. Any quantity may be made at one time. The composition is usually put in earthen vessels, without decorations. They may be of different sizes, and, in fact, as broad as they are high, sufficiently large, however, to contain the composition. A small quantity of dry meal-powder is scattered over its surface, and a sheet of paper is tied on to secure it. It is primed with port fire match.
The effect of this mixture is evidently that of the combustion of the sulphuret of antimony, as well as of the sulphur. The nitre furnishes the oxygen to both, and, as the combustion is rapid, the metal is oxidized, probably forming the antimonic acid, as the antimony may be oxidized to the maximum. There is another view, in which this combustion may be considered. According to the present theory of the formation of sulphuric acid, by the combustion of sulphur, and nitre in leaden chambers, it appears, that sulphurous acid is first produced, and nitric oxide gas, (deutoxide of azote), is also formed; and that the latter by uniting with the oxygen of the air is changed into nitrous acid, which is then acted upon by the sulphurous acid, and is decomposed. Part of its oxygen combines with the sulphurous acid, changing it into the sulphuric, and deutoxide of azote is reproduced. In all probability, then, in the combustion of the composition of Bengal lights, the nitric oxide itself may affect the combustion of the antimony, which, as it would be enveloped in nitrous acid vapour, arising from the union of nitrous gas and oxygen, may present, in a measure, one of those cases of combustion, in which nitric oxide acts as a supporter, affording on that account a particular phenomenon. Reasoning a posteriori, this may be affected again by the formation of sulphuric acid; for a part of the sulphurous acid may be changed into sulphuric, not by its immediate union with the oxygen of the nitre, according to the old theory, but by the decomposition of the vapour of nitrous acid. This conclusion, however, is sufficient, that the nitre is decomposed, and during its decomposition, the sulphur and antimony are brought into action; that a large quantity of caloric and light is evolved, whether from the oxygen gas of the atmosphere, or the substances themselves we will not stop to inquire; and, that, in the act of combustion, the sulphur and antimony are acidified, forming new products.
It will be seen, by examining the formulæ for the composition of the white and blue-lances, that they both contain antimony, but in different proportions: thus, in the white lance, the proportion of antimony is as one to eight of sulphur, as one to sixteen of saltpetre, and as one to four of meal-powder; and in the blue-lance, as it is composed only of saltpetre and antimony, the proportion of the latter to the former is as eight to sixteen. In the composition of Italian roses, or fixed stars, the proportion of antimony is still smaller, and is as one to ten of sulphur, one to sixteen of saltpetre, and one to twelve of meal-powder. Now, by comparing these proportions with those which constitute the Bengal light composition, they will be found to differ from those compositions, into which the same substances enter; for, in the Bengal lights, the proportion of the antimony to the sulphur is as five to nine, and to the saltpetre, as five to thirty-two, or thereabout.
The inference we draw, therefore, is, that the white lance composition differs from the blue, in containing meal-powder and sulphur, and the latter from the former, in containing no sulphur, but eight times as much antimony; that the white-lance composition varies from the Bengal light, by containing one-half less of saltpetre, one-fifth less of antimony, and one-ninth less of sulphur; and that the Bengal composition differs from the blue lance composition, in having double the quantity of saltpetre, nine parts of sulphur, (the blue-light having none,) and nearly one-third less of antimony. If we attend to these proportions of the antimony, with the other ingredients, in the respective preparations, we will find, that the difference, in the proportions of the antimony, produces, with the presence or absence of the meal-powder and sulphur, and the difference also in the quantity of the latter, the phenomena or effects which characterise them. It is thus, therefore, with this, as with other preparations; only vary the proportions, and institute new equivalents, as it were, in any particular preparation, and adopt some and reject other substances, and the effects are varied agreeably thereto; and, if improvements are to be made in any composition, they can only be effected by experiment, and the investigation of the effects of new proportions, a comparison of which, with the effect of any particular composition, prepared according to a given formula, can alone determine the relative value of any new formula.
Roman candles are formed on a roller seven-twelfths of an inch in diameter, and are generally fifteen inches in length. They are choaked at one end, and tied in the usual manner. According to the nature of the charge, which we shall mention, their effect is to throw out brilliant stars, to the height of one hundred and more feet, and when arranged with marrons, they finish with a report.
After the cases are formed, and ready to be filled, the operation is performed with expedition, by tying a number of them together, and charging them in that manner. The cases are charged with the rocket composition, heretofore described, in the following way: A ladleful of composition is put in, and rammed, using seven or eight blows with the mallet; a small spoonful of powder is then added, and afterwards a moulded star. This star should fit the caliber of the case. More of the composition is then added, then meal-powder, and afterwards a star, and these are repeated in the same order, till the case is completely charged. Care must be taken in observing this order, otherwise the effect would be destroyed. In striking with the mallet, attention must also be paid, that the blows are not too violent, or the star might be destroyed. When the cases, or candles, are charged, we untie them, and roll some coarse paper round each end of them, at the extremity, and round the choak.
We may remark, that in the charging of Roman candles, as their effect depends greatly on the appearance of the stars, which issue out in succession, too much care cannot be used in preserving the star composition entire. To do this, much art is required in putting in, and ramming, the rocket composition, so as not to injure or break it. The quantity of gunpowder to each star must be small, otherwise it might burst the case. Roman candles may be fired singly or several at a time, according to the effect required. To fire one in a chandelier, for instance, it is only necessary to prime it with priming paste; but, if we wish to form batteries in an artificial fire-work, in order to produce a variety, or to mount them on fixed or moveable pieces, we may, if necessary, terminate their effect with marrons, which may be effected by uniting them in such a way as to make the fire of the one, at a given time, communicate to the other. This communication is usually made through the choak, by attaching a match, which is carried to the mouth of the marron; so that, when the candle has burnt out, the last portion of the fire may pass to the marron, the effect of which is instantaneous. If necessary, priming paste may be used to facilitate the communication of the fire. The marron may be fixed directly under the bottom of the candle, by making the whole solid by a paper cylinder, which fits over the ends of both.