GUNPOWDER

an explosive obtained _by mixing ealipetre, charcoal, and sulphur together, Its discovery is attributed ‘by some to Schwartz, a Ger. monk, an d by others to Roger Bacon. It was own as an explosive, and used as a ‘scientific amusement long before its propelling powers were known. It was ‘probably first employed as a propel lan ‘by Edward III., since he po e ed cannon. The chief combustible is charcoal, which is made from dogwood, willow, or alder. The charcoal must be free from grit and burn easily, leaving ‘little ash. When made, the charcoal ds ground, sifted, and. Sod tag & stored. ‘The sulphur, after purification by distil Nation and melting, is cast in moulds and then ground and sifted. Pota ium ‘nitrate forms a very suitable source of oxygen as it does not become deliquescent. Each constituent is weighed carefully and pa ed through a sieve of known mesh, After moistening, the materials are incorporated or moved, twisted, and turned in every direction a iron rollers working on a circular bed. The whole apparatus can be douched with water if friction causes ignition. The product is ‘mill-cake.’ The mill-cake fg pre ed and becomes pre -cake. The higher the.density..the slower is the initial rate of burning. Exce of moisture reduces the explosivene . | Tho pre -cake is broken up and granulated, the grains being afterwards separated and sorted by sieving, Final proce es give different shapes (number | of faces) to the grains to suit various requirements. The products of combustion should be nitrogen and carbon diouide as gases, and pota ium sulphate and carbonate as solids,