The potassium μ-Oxo-bis(oxodiperoxovanadate)(4-) hydrate K4[O{VO(O2)2}2]*H2O was prepared, and its X-ray powder diffraction patterns have been recorded at room temperature. The unit cell parameters were refined to a=6.7097(1) Å, b=9.9574(1) Å, c=15.8250(3) Å, β=93.69(6)°, space group P21/c (14). The sample of K4V2O11*H2O was characterized by IR spectroscopy and analytical investigation. Results of crystal structure refinement by Rietveld method are presented; final RF and Rwp are 13 and 16%, respectively.
