The electrostatic ignitibility of dust clouds and powders

The electrostatic ignitibilities of a number of varied substances in the form of dust clouds or powders have been determined under a variety of conditions; the work is divided into three pans. Results for dust clouds of magnesium, aluminium, ferro-manganese, zinc and silicon are given; under certain circumstances granular aluminium presents an electrostatic hazard of the same magnitude as magnesium. The minimum condenser energies required for the ignition of dust clouds of tetryl, acaroid resin, polymethyl methacrylate. sugar and flowers of sulphur are 0·012, 0·017, 0·5, 0·009 joules respectively; the effect on these ignitibilities of including a resistance in the discharge circuit aid of varying the size of the capacity is discussed. The electrostatic ignitibilities of guncotton and cordite in the dry state are 0·012 and 0·10 joules respectively. The effect of moisture content on the ignitibility of guncotton and the effect of panicle size, nitrogen content, and the size of the discharging capacity on the ignitibilities of nitrocellulose, guncotton and cordite is discussed.