PURPOSE: To enable the highly efficient removal of oxygen, by a simple structure constituted of a cylinder formed of an electrically bad conductor, granular pure iron allowed to fill the cylinder and a power source for generating heat in pure iron by current supply.
CONSTITUTION: A column 7 is filled with granular pure iron 14 with a particle size of several mm or less and the gas flowed in from a gas introducing port 9 passes between pure iron granules and exhausted from an exhaust port 10. Because pure iron is granular, contact resistance is high and, when a current is supplied to granular pure iron from a power source 13 through electrodes 11, 12, heat is generated by the resistance thereof and the whole is heated to a temp. (about 200°C) easy to generate reaction. When gas such as N 2 or Ar is introduced into the column, a slight amount of O 2 -gas mixed in the gas, when the gas passes along the surface of granular pure iron, generates chemical reaction with pure iron and a Fe 2 O 3 -compound is precipitated on the surface of granular pure iron.