PURPOSE: To obtain the subject mixture by decomposition of a slight peroxide from an inexpensive starting material by mixing specific soda water glass with a compd. of a specific pH value, heating this mixture in an autoclave in the presence of a kenyaite seed crystal and cooling the mixture, then adding H2O2 thereto and isolating the solid.

CONSTITUTION: One Mol soda water glass having a molar ratio of SiO2:Na2O =1:(0.25 to 0.5) is mixed with a 0.1 to 0.9 mol compd. having a pH value smaller than 10.5 in an aq. molar concn. as a neutralizing agent until the ratio of SiO2:Na2O=(4 to 20):1 is attained in the reaction soln. This mixture is then heated for 1 to 10 hours to a temp. of 373 to 523 K, more particularly 453 to 493 K within the autoclave in the presence of the kenyaite seed crystal, and after cooling, 0.15 to 1.5 mol H2O2 per 1 mol used soda water glass is added to the mixture. The solid is isolated as a dry material from the reaction suspension, by which the mixture composed of the synthetic crystalline kenyaite and the salt which splits off oxygen is produced.