text: Frémy's salt, being a long-lived free radical, is used as a standard in electron paramagnetic resonance (EPR) spectroscopy, e.g. for quantitation of radicals.  Its intense EPR spectrum is dominated by three lines of equal intensity with a spacing of about 13 G (1.3 mT).
  The inorganic aminoxyl group is a persistent radical, akin to TEMPO.
  It has been used in some oxidation reactions, such as for oxidation of some anilines and phenols allowing  polymerization and cross-linking of peptides and peptide-based hydrogels.
  It can also be used as a model for peroxyl radicals in studies that examine the antioxidant mechanism of action in a wide range of natural products.