Magnesium Metatungstate, MgW₄O₁₃

Magnesium Metatungstate, MgW₄O₁₃.8H₂O, is obtained by double decomposition. It yields lustrous monoclinic prisms with

a:b:c = 0.6763:1:0.7792; β = 106° 43'.

Manganous Metatungstate, MnW₄O₁₃.10H₂O, is also obtained by double decomposition. It forms beautiful light yellow quadratic octahedra, a:c = 1:0.9919, permanent in the air. On heating at 100° C. to 110° C. it loses 7H₂O, the remaining 3H₂O only being expelled at a much higher temperature.