In making gunpowder, the components, the sulphur, nitre, and charcoal should be as pure as possible, and reduced to the finest possible powder; they are sifted and mixed in the proper proportions. The mixture is then made into a cake with water, and ground between calcareous millstones. It is then granulated through sieves in another mill, and again sifted. It is then polished and hardened by revolving rapidly in a cask, and finally dried. The proportions of the constituents vary in different countries; at Waltham Abbey they are seventy-five nitre, fifteen charcoal and ten sulphur. The quantity of gunpowder consumed in this country is enormous; moreover, 4,000,000 lbs. are annually exported, the greater part of which is sent to the western coast of Africa.
The force of the explosion of gunpowder is owing to the sudden disengagement of gaseous products; these consist of nitrogen, carbonic oxide, carbonic acid, and sulphurous acid gases; and their volume has been calculated to amount to 2000 times the bulk of the powder.]
FOOTNOTES
[1190] To this subject belong the following works:—Ars Magna Artilleriæ, Auct. Cas. Siomienowicz. Amst. 1650, fol. p. 61. The author thinks that the nitrum of the ancients is not at present known.
Natural History of Nitre, by W. Clarke. Lond. 1670, 8vo. It is here said that the nitrum of the ancients was impure saltpetre, and that the latter is produced from the former by purification.
G. C. Schelhameri de Nitro, cum veterum, tum nostro commentatio, Amst. 1709, 8vo, contains good philological observations, particularly in regard to the period, but leaves the question undetermined.
Saggi sul ristabilimento dell’ antica arte de’ Greci e Romani pittori, del Sig. Doct. Vin. Requeno. Parma, 1787, 2 tomi in 8vo, ii. pp. 95, 131: a learned but diffuse work. He thinks that the nitrum of the ancients was our saltpetre; and what others consider as proofs of its being mineralized alkali, he understands as indicating alkalized saltpetre. I am not, however, convinced. Before I ascribe to the ancients a knowledge of our saltpetre, I must be shown in their writings properties of their nitrum sufficient to satisfy me that it was the same substance.
Commentat. de nitro Plinii, in J. D. Michaelis commentationes. Bremæ 1784, 4to. The author only illustrates the account of Pliny, and states what, according to his opinion, we are to understand in it in regard to alkali, and what in regard to our saltpetre.
[1191] [Since the discovery of the immense deposits of nitrate of soda in Peru, this salt, from its being much cheaper, has replaced the nitrate of potash in the manufacture of aquafortis, but it is not adapted to the making of gunpowder owing to its deliquescent property.]
[1192] I found the account of the Portuguese saltpetre in Mémoires Instructifs pour un Voyageur. The author of this work was the well-known Theodore king of Corsica.