a chemical seal for isolating the liquid phase of a contained liquid from the vapor phase present in the container headspace comprises a chemically impregnated gel formed by mixing a biopolymer gel , a high molecular weight polymer and chemical impregnants with water to form a gel - forming aqueous solution which is applied to the surface of the contained liquid and allowed to solidify thereby forming a mechanically stable , chemically impregnated gel seal in intimate contact with the contained liquid .