Process of producing hydrogen and oxygen from H/sub 2/O in a thermochemical cycle. [steam, SO/sub 2/, and oxide of one of metals Mn, Fe, Co, Ni, Zn, and Cd]

A method is proposed for producing hydrogen and oxygen by splitting water in a thermochemical cycle, according to which in a first method stage a gas mixture of from 1 to 50 parts by volume of steam and 2 parts by volume of sulfur dioxide is reacted at a temperature within the temperature range of from 200 to 400/sup 0/C with an oxide of one of the metals manganese, iron, cobalt, nickel, zinc or cadmium for forming a metal sulfate and for freeing hydrogen gas. Thereupon the hydrogen gas is in a manner known per se separated from the residual gas mixture and in a second method stage after conversion of the metal oxide to a metal sulfate, the metal sulfate for purposes of decomposition or disintegration and for forming a metal oxide, sulfur dioxide gas and oxygen gas, is heated to a temperature within the temperature range of from 700/sup 0/ to 1000/sup 0/C. Thereupon the oxygen gas is separated from the sulfur dioxide gas in a manner known per se.