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D-(+)-Gluconic acid δ-lactone (GDL) is soluble in water and hydrolyzes into gluconic acid spontaneously and homogeneously lowers the pH.
G 4440 (OTTO) D-(+)-Gluconic acid δ-lactone, ≥99% Cas 90-80-2 - used in the preparation of cold set gels, and hydrogels.