Calcium Disodium EDTA is a preservative used to prevent catalytic oxidation by metal ions and for iron fortification. It removes metal impurities in food thus preventing rancidity. This safe chemical is used in preventing rancidity in salad dressing, margarine, sandwich spreads, mayonnaise, processed fruits and vegetables, canned shellfish, and soft drinks. Used to treat metal poisoning in people. Found to be harmfull in large doses because it limits mineral metabolism.