Highly oxidizing compound; decomposes to produce nitroxyl (HNO). Prepn: A. Angeli, Gazz. Chim. Ital. 26, 17 (1896); and uv spectrum: C. C. Addison et al., J. Chem. Soc. 1952, 338. Crystal structure of monohydrate: H. Hope, M. R. Sequeira, Inorg. Chem. 12, 286 (1973). Reactivity studies: P. A. S. Smith, G. E. Hein, J. Am. Chem. Soc. 82, 5731 (1960); L. Torun et al., Tetrahedron Lett. 40, 5279 (1999). Decomposition studies: F. T. Bonner, B. Ravid, Inorg. Chem. 14, 558 (1975); C. M. Maragos et al., J. Med. Chem. 34, 3242 (1991). pH-dependent cytotoxicity: D. A. Stoyanovsky et al., ibid. 47, 210 (2004).