Abstract
The paper deals with the condition of preparation of a condensed phosphate pigment, Mineral Violet, and it's chemical composition including the state of phosphate and valence of Mn ion by several analytical methods.
The Mineral Violet was obtained by heating the mixtures of manganese (IV) oxide and am monium dihydrogenphosphate in a mole ratio of 1/8-10 for 1.5 hours at 260°C. The hue of the pigment showed vivid reddish purple (complementary wavelength λc ; 554.4nm, lightness Y;10.6%, excitation purity Pe; 48.7%). From paper chromatographic analysis, di-and orthophosphate groups were recognized to coexist together and the ratio was considerably affected by the preparation temperature. Also the complex ion MnP2O7-formed by bonding the both of manganese ion and diphosphate group. In addition, the valence number of manganese was confirmed to be trivalent from fluorescent X-ray and infrared spectra data. The decomposition of Mineral Violet started at about 362°C and then converted to Mn3 (P3O9) 2 at about 550°C.
