The equilibrium relation among D-glucosaccharic acid and its lactones (nemely 1, 4-and 6, 3-monolactones and 1, 4 : 6, 3-dilactone) in aqueous solution was investigated. It was found that the dilactone was detectable only at elevated temperature, and that the amount of the 1, 4-lactone in equilibrium was almost indifferent to temperature.
