1087.    FRICKE, R., AND ACKERMANN, P.  [Heat Content and Lattice Structure of Active Ferric Oxide.]  Ztschr. Elektrochem., vol. 40, 1934, pp. 630-640; Chem. Abs., vol. 29, 1935, p. 33.

        The lower the temperature of dehydration of synthetic microcrystalline a-FeOOH, the greater is the energy content of the resulting a-Fe₂O₃; the energy differences as shown by heats of solution may reach 5 kcal. per mol. Fe₂O₃.  Quantitative photometric measurements of x-ray powder photographs show imperfect lattice formation of the low-temperature Fe₂O₃, rather than differences in particle size or in lattice dimensions relative to the high-temperature Fe₂O₃.  Tempering at 220° increases the lattice perfection of low-temperature Fe₂O₃ and restores its energy content to normal.