It is applied in luminol-type chemiluminescent reactions as a fluorescent probe in analytical reagents for detecting metal ions and in organic synthesis for heterocycles.

Its purpose includes generating light in oxidation reactions for bioassays serving as an intermediate in dye and pharmaceutical synthesis and acting as a ligand in coordination chemistry.

Phthalhydrazide (CAS 1445-69-8) also known as 23-dihydrophthalazine-14-dione is a white to off-white crystalline solid with formula CHNO molecular weight 162.15 gmol melting point 300 C soluble in acetone and acetic acid and used as a reagent in chemiluminescence studies