A new tungsten trioxide hydrate, WO3 · 13H2O: Preparation,characterization, and crystallographic study

A new hydrate of tungsten trioxide, $\text{WO}{}_3\text{·}\text{1}\text{3}\text{H}{}_2\text{O}$ has been obtained by hydrothermal treatment at 120°C of an aqueous suspension of either tungstic acid gel or crystallized dihydrate. This hydrate has been characterized by different methods. A crystallographic study was carried out from X-ray powder diffraction. The hydrate crystallizes in the orthorhombic system: a = 7.359(3) Å, b = 12.513(6) Å, c = 7.704(5) Å, Z = 12. The existence of structural relationships between the hydrate, $\text{WO}{}_3\text{·}\text{1}\text{3}\text{H}{}_2\text{O}$, and the product of dehydration, hexagonal WO₃, has permitted us to propose a structural model in agreement with the experimental data. $\text{WO}{}_3\text{·}\text{1}\text{3}\text{H}{}_2\text{O}$ must be regarded as an interesting compound because its dehydration leads to a new anhydrous tungsten trioxide, hexagonal WO₃.