An outline of the crystal-structure of Bi\u3csub\u3e2\u3c/sub\u3eMo\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e9\u3c/sub\u3e

\u3cp\u3eAn outline of the structure of the catalyser component Bi\u3csub\u3e2\u3c/sub\u3eMo\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e9\u3c/sub\u3e has been determined from X-ray powder diffractometer diagrams. The space group is P\u3csup\u3e2\u3c/sup\u3e l n (= P\u3csup\u3e2\u3c/sup\u3e l c) with cell constants: a = 11.946 (2) A ̊, b = 10.795 (2) A ̊, c = 11.876 (2) A ̊ and β = 90.15 (2)°. There are eight formula units per cell. The positions of the metal-ions could directly be derived from the intensities of the strongest reflexions. With difference terms calculated from 19 strong reflexions a Δ F-synthesis was calculated, which revealed the approximate positions of the O\u3csup\u3e2-\u3c/sup\u3e-ions. From packing considerations it was apparent that of 9 0\u3csup\u3e2-\u3c/sup\u3e-ions one is only coordinated by Bi\u3csup\u3e3+\u3c/sup\u3e and that Mo\u3csup\u3e6+\u3c/sup\u3e must be tetrahedrally surrounded by 0\u3csup\u3e2-\u3c/sup\u3e. These tetrahedra may be strongly distorted. The structure is not related to the scheelite-structure as has been assumed by some authors.\u3c/p\u3