It is primarily used as a colorimetric reagent for detecting calcium and magnesium ions in analytical chemistry forming purple-red complexes and historically in purpuric acid tests for qualitative analysis.

Its main purpose is to provide sensitive selective complexation with alkaline earth metals (especially Ca) in ammoniacal solution producing measurable color changes for titration endpoints or spot tests.

Murexide (C8H8N6O6) also known as ammonium purpurate is a purple-red crystalline solid with a green metallic luster derived from alloxan and ammonia featuring two barbituric acid units linked by an imine bond with molecular weight 284.19 gmol and absorption maximum at 520 nm.