UPSC NDA I 2015 General Ability Solved Paper

Commercial black powder looks black because the little lumps of the stuff are coated with graphite. In the manufacturing process, the powder's mixed with water or some other liquid binder, pressed into cakes and dried, then crushed and screened into powders of various particle size, larger particles producing a slower burn. The graphite serves no chemical purpose, but it lubricates the particles, and also makes the bulk powder electrically conductive enough that it is unlikely to initiate proceedings unexpectedly because of a static electricity spark.