Electric arc apparatus

PCT No. PCT/GB78/00054 Sec. 371 Date Aug. 13, 1979 Sec. 102(e) Date Aug. 13, 1979 PCT Filed Dec. 19, 1978 PCT Pub. No. WO79/00413 PCT Pub. Date Jul. 12, 1979.Apparatus for treating a flow of material by an electric arc generates free radicals and/or atoms, and charged species, in ground or excited states. A cathode (13) and an anode (14) are arranged for striking an arc across a preferably annular gap and provide a pathway for flow of material through the gap between the cathode and anode. Each electrode has a region providing a continuous closed path for the anode spot or cathode root respectively to travel around, and means, preferably magnetic means (19), for producing movement of the arc cause the anode spot and cathode root to travel around their paths in the same sense and in substantially the same time. Preferably the paths are circular paths in parallel planes on the anode and cathode respectively, and the length of the arc remains substantially constant during travel of the anode spot and cathode root around the paths. Preferably the cathode (13) comprises a rod having a plane end face with a circumferential edge for striking the arc. Preferably the cathode has a sharp edge for striking the arc and for providing the said continuous closed path for the cathode root.