Abstract: A gas sensor wherein a first electrode whose surface is covered with an oxidizing catalyst, and a second electrode which is made of the same material as that of the first electrode and whose surface is exposed and can come into direct contact with a gas to-be-detected are disposed on a solid electrolyte which exhibits an oxygen ion conductivity.Since the gas sensor of this invention has the electrodes formed of the identical material, it has over a prior-art gas sensor the merits that secular changes are very little and that the operation is possible even at low temperatures. It can readily detect a combustible gas on the order of several tens p.p.m.

Abstract: A catalyst comprising carbonaceous materials such as activated carbon, etc. impregnated with bromine, iodine, chlorine or their compounds, is impregnated with a promoter containing a specific metal, and brought in contact with a flue gas in the presence of ammonia, whereby nitrogen oxides and sulfur oxides contained in the flue gas are removed with a very high percent removal. The removal can be carried out at a temperature much lower than that of the conventional process.

Abstract: Carbonaceous materials are impregnated with bromine, chlorine, iodine or their compounds, and brought in contact with a flue gas in the presence of ammonia, whereby nitrogen oxides and sulfur oxides contained in the flue gas are trapped by the carbonaceous materials and can be removed from the flue gas with a very high percent removal.

Abstract: A magnetic recording medium or composition which comprises a ferromagnetic chromium dioxide product containing a proper quantity of tungsten alone or admixed with a member selected from the group consisting of copper and zinc, which has an excellent ferromagnetic characteristic of high coercive force.