GUNPOWDER is a mixture of saltpetre, sulphur and char coal in such proportions that, when a part is heated to a certain temperature, combustion takes place with great rapidity through the bulk in contact and an explosive effect is produced. It may be more correct to speak of the introduction than of the invention of gunpowder, for Friar Roger Bacon chanced upon it as the result of obtaining nearly pure nitre. (See EXPLOSIVES.) The honour has, however, also been associated with the name of Ber thold Schwartz, a German monk, of whom O. Guttmann writes (Monuments pulveris pyrii, P. 6, 1904) : "Berthold Schwartz was generally considered to be the inventor of gunpowder, and only in England has Roger Bacon's claim been upheld, though there are English writers who have pleaded in favour of Schwartz. Most writers are agreed that Schwartz invented the first firearms, and as nothing was known of an inventor of gunpowder it was per haps considered justifiable to give Schwartz the credit thereof. There is some ambiguity as to when Schwartz lived. The year is sometimes mentioned as the date of his invention of powder, and this is also to be inferred from an inscription on the monument to him in Freiburg. But considering there can be no doubt as to the manufacture in England of gunpowder and cannon in 1344, that we have authentic information of guns in France in 1338 and in Florence in 1326, and that the Oxford ms. De officiis regum of 1325 gives an illustration of a gun, Berthold Schwartz must have lived long before 1354 to have been the inventor of gunpowder or guns." In Germany also there were powder-works at Augsburg in 134o, in Spandau in 1344, and Lieg nitz in 1348. An indenture first published by Sir N. H. Nicolas (History of the Royal Navy, 1846) and later by Col. Bracken bury (Proc. R. A. Inst., 1865), stated to be of 1338, contains references to small cannon as in the stores of the Tower, in London, and also mentions "a small barrel of gunpowder." In the Record Office, in London, also are trustworthy accounts of the purchase of ingredients of powder (starting with the year and of the shipping of cannon to France, and in 1346 Edward III. ap pears to have ordered all the available sulphur and saltpetre to be bought up for him. The manufacture of gunpowder seems to have been carried on as a Crown monopoly about the time of Elizabeth, and regulations respecting gunpowder and nitre were made about 1623 (James I.) . Powder-mills were probably in existence at Waltham Abbey, England, about the middle or towards the end of the i 6th century.
Roger Bacon, in his anagram, gives the first real recipe for gunpowder (see Hime, Gunpowder and Ammunition, 1924), viz., saltpetre 41.2, charcoal 29.4, sulphur 29.4%. Dr. John Arderne of Newark, who began to practise about 13 5o and was later surgeon to Henry IV., gives a recipe (Sloane mss. 66.6, charcoal, 22.2, sulphur 11.1 %, "which are to be thoroughly mixed on a marble slab and then sifted through a cloth." This powder is nominally of the same composition as one given in a ms. of Marcus Graecus, but the saltpetre of his formula was un doubtedly answerable for the difference in behaviour of the two compositions. Roger Bacon had not only refined and obtained pure nitre, but had appreciated the importance of mixing thor oughly the components of the powder. Most if not all the early powder was a "loose" mixture of the three ingredients, and the most important step in connection with the development of gun powder was undoubtedly the introduction of wet mixing or "in corporating." Whenever this was done the improvement in the product must have been immediately evident. In the damp or wetted state pressure could be applied with comparative safety during the mixing. The loose powder mixture came to be called "serpentine"; after wet mixing it was more or less granulated or corned and was known as "corned" powder. Corned powder seems to have been gradually introduced; it is mentioned in the Fire Book of Conrad von Schongau (1429). It would seem that corned powder was used for hand-guns or small arms in the 15th century, but cannon were not made strong enough to withstand its explosion for quite another century (Hime). According to the same writer, in the period 1250-145o, when serpentine only was used, one powder could differ from another in the proportion of the ingredients; in the modern period, say 1700-1886, the powders in use (in each state) differed only as a general rule in the size of the grain, whilst during the transition period, 1450-1700, they generally differed both in composition and size of grain. Corned or grained powder was adopted in France in 1525, and in 154o the French utilized an observation that large-grained powder was the best for cannon and restricted the manufacture to three sizes of grain or corn, possibly of the same composition. Early in the i8th century two or three sizes of grain and powder of one compo sition appear to have become common. The composition of gun powders used in different countries at different times is illustrated in the following tables: The last column in the preceding table represents brown or coco-powder for large charges in guns. The charcoal involved is not burnt black but is roasted until brown, and is made, not from wood, but from some variety of straw. When reasonably pure, none of the ingredients of gunpowder absorbs any material quan tity of moisture from the atmosphere, and only the nitre is a soluble substance. The three substances were often mixed dry, just before being required ; since saltpetre is considerably heavier than sulphur or charcoal, it would tend to separate out towards the bottom of the containing vessel and hence, with dry mixing, the proportions of the three ingredients would alter on carriage. Salt petre and sulphur are chemical individuals and therefore, if pure, are always of the same composition, but this is not the case with charcoal—its composition, rate of burning, etc., depend not only on the nature of the woody material from which it is made, but quite as much on the temperature and time of heating employed in the making (see CHARCOAL). The woods from which it is made contain carbon, hydrogen and oxygen, and the last two are never thoroughly expelled in charcoal-burning. If they were, the resulting substance would be of no use for gun-powder: 1-3% of hydrogen and 8-15% of oxygen generally remain in charcoals suitable for gunpowder. A good deal of the fieriness and violence of explosion of a gunpowder depends on the mode of burning of the charcoal, as well as on the wood from which it is made.
Sicilian sulphur, which is most generally employed for gun powder, is purified by distillation, melting and moulding. It is afterwards ground into a fine powder and sifted as in the case of charcoal.
The grains are freed from dust by being revolved in slightly tilted frames covered with 20-mesh gauze. They are then polished in order to diminish the tendency to absorb moisture—the process also increases the density. This is effected by rotation for 5–I o hours in large drums, the friction producing a brilliant glaze without the use of graphite in this type of powder. Other powders are run for shorter periods with about I oz. of graphite per 1 oo lb. of powder. The powders are placed in open-work shelves in a drying room heated by steam to about 40° C, the moist air being carried off by efficient ventilators. Even and sloe% drying is best, for rapid drying tends to crack the grains ; the tim€ required is from I to 6 hours, depending on the size of grain and the moisture content. In this process the powder is rotated in long, horizontal, cylindrical wooden frames covered with canvas, whereby it is freed from the dust produced in drying and given a final glaze. At several stages in the manufacture, the various batches are mixed or "blended" in order to produce as uniform a product as possible.
The following data are approximate values for average powders and do not apply to powders of special composition for particular purposes, such as mining powders. According to Noble and Abel, I gr. of dry powder produces 720-800 gram-calories of heat on explosion, attaining a temperature of about 2,100° C, and giving 200-300 cu-cm. of permanent gases (i.e., gases which do not con dense to liquids on cooling to the ordinary temperature). The composition of these permanent gases (percentage by volume) is roughly: Carbon dioxide . . . 5o Sulphuretted hydrogen . 3 Carbon monoxide . . Io Hydrogen . . . 2 Nitrogen . . . . 35 Methane and oxygen . traces The composition of the dry solid residue (percentage by weight) is approximately : Potassium carbonate . . 56 Potassium thiocyanate . Potassium sulphate . . 16 Potassium nitrate . . 0•2 Potassium sulphides . . 25 Charcoal and (mono- and poly-) ammonium carbonate traces Variations in conditions of burning may alter the foregoing pro portions very appreciably.