A chemically active composition containing divalent iron ions, wherein an iron (II) compound, ascorbic acid and or citric acid and alum are contained and the ratio between the divalent iron ions in the iron (II) compound and ascorbic acid or citric acid is between 1:0.02 and 0.30 (in the case of ascorbic acid) or 1:0.01 and 0.80 (in the case of citric acid) by weight ratio. The composition is applied in the form of an aqueous solution or solid matter as a deodorant, freshness-preserving agent for foods, growth promoting agent for plants and flame retardant for burnable materials. Not only uni-functional materials can be obtained but also multi-functional materials.