Preservatives can be volatile, unstable, or stable. Volatile preservatives such as ethylene oxide and propylene oxide are used in the sterilization of spices. Unstable preservatives such as diethylpyrocar- bonate and hexamine are only used in a few foods and are not per mitted in most countries. Diethylpyrocarbonate readily hydrolyzes to yield ethanol and carbon dioxide, as follows It has been suggested for use in beverages at a concentration of 30 to 200 ppm immediately before bottling and closing. Hydrolysis is com plete in aqueous systems at pH 2.8 and 20 C. Questions about safety of diethylpyrocarbonate have arisen because of possible reactions with amino acids that result in the toxicologically suspect compound urethane or in carbamic acid ethy