Abstract: A first partial flow of an H.sub.2 -air-steam mixture is passed through a first channel and recombined by contact with a first channel wall having a catalytic coating. In addition to the first partial flow, a second partial flow of the mixture is passed through a second channel having a second channel wall and is ignited by being fed past preferably metallic ignition elements being heated to the H.sub.2 ignition temperature upon reaching or exceeding an ignition limit. Under these circumstances, heat liberated during the catalytic reaction in the first channel is at least partially transmitted to the second channel for the purpose of preheating it. The novel process functions both at the lower and at the upper ignition limit and recombines even at unignitable H.sub.2 concentrations. A device with which the process can be carried out is also described.

Abstract: Crystals of the Zeolite Analcime (Analcite) Na.sub.2 O.Al.sub.2 O.sub.3.4SiO.sub.2.2H.sub.2 O are provided having a largest dimension greater than 50 micron. A method for preparing such crystals by mixing aqueous solutions of aluminium sulphate and sodium metasilicate, allowing a gel to form then heating, is provided. The presence of an organic water-miscible base encourages an increased crystal size. The crystals retain water strongly and a use for them in long term immobilisation of tritiated waste water is provided.