Maricite and sodium iron hydroxyphosphate (SIHP) are recently discovered iron(II) and iron(III) compounds that play a major role in phosphate "hideout" and corrosion in highpressure boilers. This paper reports a novel method for synthesizing maricite by thermally decomposing the complex of aqueous iron(III) nitrilotriacetic acid at 200 °C and methods for the hydrothermal synthesis of SIHP from Fe 3 O 4 or FePO 4 . The crystal structure of maricite is identical to the impure natural mineral (Le Page Y.; Donnay G. Can. Mineral. 1977, 15, 518-521). The X-ray diffraction pattern of SIHP is consistent with an orthorhombic unit cell containing 8 units of formula Na 3 Fe(PO 4 ) 2 ‚(Na 2(1-x) H 2x O), with x ) 0.226 ( 0.025. This is similar, but not identical, to the formula Na 4 Fe(OH)(PO 4 ) 2 ‚ 1 / 3 NaOH proposed by Ziemniak and Opalka (Proc.

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