Single crystals of the hydrated potassium orthovanadate phases K₃(VO₄)·0.56H₂O, tripotassium orthovanadate 0.56-hydrate, and K₃(VO₄)·4H₂O, tripotassium orthovanadate tetrahydrate, were isolated during the processing of products obtained under hydroflux conditions. The asymmetric unit of K₃(VO₄)(H₂O)₀.₅₆ (space group P1, Z = 12) comprises six formula units of K₃(VO₄) and five water molecules of crystallization. The complex crystal structure is made up of isolated [VO4]³⁻ tetrahedra connected via K+ cations exhibiting coordination numbers between 6 and 8. The structure is consolidated by the formation of a finite hydrogen-bonded network between the water molecules and [VO4]³⁻ tetrahedra. Two of the K+ cations are positionally disordered, and three of the water molecules of crystallization are occupationally and/or positionally disordered. The asymmetric unit of K₃(VO₄)(H₂O)₄ (space group Pmn21, Z = 2) comprises two K+ cations, one VV atom, three O atoms and two water molecules. The crystal structure is also made up from isolated [VO₄]³⁻ tetrahedra interlinked by K+ cations (coordination numbers 7 and 8). In comparison with the less-hydrated phase, the higher water content of this compound results in an infinite network of O—H⋯O hydrogen bonds between the water molecules and [VO₄]³⁻ tetrahedra.
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