Exists as tetrahydrate. Identification: A. Joly, C. R. Hebd. Seances Acad. Sci. 115, 1299 (1893). Prepn and structure: Fletcher et al., J. Chem. Soc. 1961, 2000. M"ossbauer study: Clausen et al., Inorg. Nucl. Chem. Lett. 7, 485 (1971). Alternate structure and composition: Sterling, Am. J. Bot. 57, 172 (1970). Use as microscopic stain: L. Mangin, C. R. Hebd. Seances Acad. Sci. 116, 653 (1893); in electron microscopy: R. Dierichs, Histochemistry 64, 171 (1979). Differential staining: P. R. Blanquet, ibid. 47, 175 (1976); M. G. Gutierrez-Gonzalvez et al., J. Microsc. 145, 333 (1987). Series of articles on chemistry, mechanism of action, specific uses: Anat. Rec. 171, 347-442 (1971). Conversion in situ to ruthenium violet: J. R. Luft, ibid. 347; M. G. Guiterrez-Gonzalvez et al., loc. cit.