Bones, and other hard parts of animals, when subjected to distillation, furnish several products, as impure ammonia, animal oil, and the like. Wood also, we remarked, when treating of its carbonization for the formation of coal, produces, besides gaseous and other volatile products, the result of its decomposition, a quantity of acid liquor, formerly called the pyroligneous, but now the pyroacetic acid. By separating the empyreumatic flavour, which at first constitutes a part of the acid, the acetic acid is obtained in a state of purity. The pyro-tartaric acid is also the result of the action of heat; and we know, when animal substances are calcined with potash, they produce cyanogen, the basis of the hydrocyanic and ferrocyanic acids, the latter of which when united with the peroxide of iron, forms the perferrocyanate of iron, commonly called Prussian blue. Caromel also, that peculiar substance which is disengaged from sugar and various saccharine substances, when submitted to the action of heat, is a product, resulting from the decomposition of the sugar. The empyreumatic, or burnt flavour of certain distilled liquors, which is corrected by redistillation with charcoal, or passing the liquor through a filter of charcoal, is owing to the same cause. The changes, that bodies undergo by partial roasting, are familiar to every one; as, for instance, the torrefaction of barley, after germination, in the preparation of malt, the degree of which determines the colour and taste of the beer; the roasting of rye and coffee, before they can be employed to form a beverage; and the torrefaction of the cocoa, before it can be made into chocolate, the sweet taste and brown colour of which are acquired in the process, are all examples of the effect of heat on bodies. The action of heat, according to its temperature, produces, therefore, effects of a particular kind; and, as we regulate the heat in such cases, we form products of different kinds. Destructive distillation, however, would again change the character of these products. Of this kind, we may consider the effect of the heat, produced in the combustion of inflammable substances. In a word, the action of heat may be so graduated, in the same manner as the tempering of steel, as to produce only partial changes, which must ensue at certain temperatures; or, by an increment of heat, in which a total decomposition takes place, the effect is regulated, by the force of affinities, exerting their influence under modified circumstances. Hence we perceive, by reasoning a priori, that as substances are altered by the action of heat, so they produce new compounds, according to the circumstances of the action, and with or without the agency of foreign bodies. These facts are so far applicable to the subject under consideration, as to enable us to explain, or account for the effects that result on the mixture, or combustion, of bodies, a knowledge of which is undoubtedly necessary to form a theory of fire-works in general.
[CHAPTER V.]
OF MATCHES, LEADERS, AND TOUCH PAPER.
We purpose, in the fourth part of our work, to go into the detail of the manufacture of various kinds of matches, which belong more particularly to military pyrotechny, adding, at this time, that fire matches are differently formed, and are called the quick and slow match. The former is commonly made of three cotton strands, drawn into lengths, and put into a kettle, and just covered with vinegar, (usually white wine vinegar), a quantity of saltpetre and meal powder being added, and the whole boiled together. Some put only saltpetre into water, and, after soaking the cotton, place it, while hot, in a trough with some meal powder, moistened with some spirits of wine, or brandy, which are thoroughly worked into the cotton, by rolling it backwards, and forwards with the hands. When this is done, they are taken out separately, and, after being drawn through meal powder, dried upon a line. Another mode is to steep the cotton first in vinegar, and then rub into it the following composition:
Composition for quick-match.
| Vinegar in which matches are soaked, | 2 | quarts. |
| Brandy, | 1 | do. |
| Saltpetre, | ½ | lb. |
| Priming powder, | 1 | do. |
| As much cotton as will take up all the above, which will be about, | 1 | do. |
To the proportions of one pound and three-quarters of cotton, one pound of saltpetre, two quarts of spirits of wine, one pound of meal powder, and three quarts of water, some recommend the addition of four ounces of isinglass, dissolved in three pints of water.
Another method is to steep the matches in brandy, and then rub them well with priming powder.