Crystal data for α‐, β‐ and γ‐Ag2WO4 were collected from Cu Kα1 powder diagrams, α‐Ag2WO4 is orthorhombic (Pn2n) with a = 10.820(2), b = 12.018(2) and c = 5.900(1) Å. β‐Ag2WO4 is hexagonal (P63 or P63/m) with a = 11.0925(3) and c = 7.5424(4) Å. γ‐Ag2WO4 is cubic (Fd3m, spinel type) with a = 9.352(1) Å.

Mr=106.17, monoclinic, P21/n, a=5.806(2), b=

Some of the high-temperature phases of K2MoO4, K2WO4 and Rb2WO4 are shown to have modulated structures. The modulation wave vector k is rationally independent of the basic vectors of the unit cell. The diffraction patterns have symmetry 6/mmm. The k vector points in the direction of the a* axis; k= tea*. For K2MoO4 the value of x changes continuously from 0.297 at 360°C to 0.290 at 430°C. The values for K2WO4 and Rb2WO4 are 0-250 at 395 °C and 0.363 at 435°C respectively. A model for the modulation is proposed. In this model the modulation is assumed to be a periodic change in the orientations of the anion tetrahedra.

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