Crystal data for ferric molybdate: Fe₂(MoO₄)₃

Indexed powder patterns of the monoclinic phase, stable at room temperature, and of the orthorhombic phase, stable for T > 786 K, are given. The cell dimensions are: a = 15.737 (8), b = 9.231 (5), c = 18.224 (9) Å, β = 125.46 (2)° at 295 K; a = 9.330 (3), b = 12.868 (5), c = 9.242 (3) Å at 818.6 K. Linear equations describing the thermal expansion of the two phases of ferric molybdate are reported. To verify if ferric molybdate can incorporate excess MoO₃, measurements on non-stoichiometric samples were also made: no evidence of the presence of excess MoO₃ was found.