The structure of hydrohematite

Hydrohematite beside 'weakly bound' water removable at 1602000e, contains about 3-4.5 %of tightly held H20, the complete withdrawal of which requires a very high temperature, of about 10000 C. IR investigations have shown that this kind of water exists in the form of hydroxyl groups. For this reason it has been assumed that OHions occupy anion positions in the close-packed anionic sublattice of hematite together with oxygen anions and that the electrostatic neutrality is preserved by Fe3 + deficiency in the cationic positions. Accurate measurements of X-ray reflection intensities of hydro hematites revealed a decrease in intensity of all reflections due to Fe3 +, and an unchanged intensity of (113)-reflection. The intensity of this reflection is exclusively dependent on anions. The results obtained agree well with the calculated values for the model assumed and fully confirm the defect character of hydro hematite structure. Thus the formula of hydrohematite should be written Fe2-iOH)x03-x'