Ethylene oxide is extracted by circulation with distilled water in a closed circuit at 37 degrees . The circulation time, volume and flow of the water are previously determined as a function of the apparatus characteristics. The extract is analysed either by gas-liquid chromatography (direct injection with propylene oxide as internal standard) or by spectrophotometry. The latter method consists in the periodate oxidation of ethylene glycol in two samples of the same extract, with and without acid hydrolysis, followed by determination of formaldehyde with chromotropic acid. The difference between the absorbances of the two samples gives the quantity of ethylene oxide in the extract. A reasonable correlation of the two sets of results is observed, and the choice between these two simple methods depends on the number of samples to be analysed and on the equipment available. The spectrophotometric method is the longer of the two.