Adipic acid dihydrazide (ADH) is a chemical used for cross-linking water-based emulsions. It can also be used as a hardener for certain epoxy resins.[2] ADH is a symmetrical molecule with a C4 backbone, and the reactive group is C=ONHNH2. Dihydrazides are made by the reaction of an organic acid with hydrazine. Other dihydrazides with different backbones are also common, including isophthalic dihydrazide (IDH) and sebacic dihydrazide (SDH).