(1E,2E)-1,2-Ethanedione 1,2-dioxime, also known as diacetyl dioxime or dimethylglyoxime. Structurally, it consists of a central ethane backbone bearing two oxime groups (=C=NOH) at each carbon of the diketone moiety, with both oxime bonds in the E (trans) configuration. It typically appears as a pale yellow crystalline solid that is sparingly soluble in water but soluble in alcohols and organic solvents. It is best known for its ability to selectively form bright red chelate complexes with nickel(II) ions, making it a widely used analytical reagent in gravimetric and qualitative analysis of nickel. Its chelating properties stem from the two oxime nitrogen atoms, which coordinate tightly to metal centers.