- a white or yellow, toxic, crystalline or powdery compound, C9H4O3⋅H2O, that reddens when heated above 100°C, a monohydrate, soluble in water or alcohol: used primarily as a reagent to detect the presence of various amino acids.
- a chemical reagent used for the detection and analysis of primary amines, esp amino acids, with which it forms a derivative with an intense purple colour
