Physical characteristics: white hygroscopic crystal or piece. It is white or grey flake,particle or massive crystallization.Apt to
cake after moisture absorption when laid in air for a long time.A little green because of Fe2+ ,yellow when Fe2+ is oxided
toFe3+.Soluble in water easily,and water solution is acid.
Usage: Treatment for the drinking water and water for industrial use. Also used in papermaking, printing and dye, tanning
leather,fire-fighting equipment, drug and wood preservation, etc.