Abstract: A solidifying agent comprising slag dust from the refining of metals, silicates, water-soluble, high molecular weight compounds, metal salts of an organic acid and calcium carbonate. The solidifying agent is useful for solidifying liquid organic halogenides into solid composites containing organic halogenides. The organic halogenides are disposed of by a burning method which comprises converting the organic halogenides to vapors and disposing the organic halogenides by burning the vapors.