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Ammonium purpurate, 99% - is the ammonium salt of purpuric acid.
A 2285 (OTTO) Ammonium purpurate, 99% Cas 3051-09-0 - used in analytical chemistry as a complexometric indicator for complexometric titrations, most often of calcium ions, but also for Cu, Ni, Co, Th and rare-earth metals.