Abstract

Crystals of KIO₃ show the space-group symmetry P 1 at room temperature. The lattice constants being: a = 8.923 Å, b = 8.942 Å, c = 7.709 Å, α = 54.4° β = 125.3°, γ = 90.6°. In this structure, which belongs to the perowskite typ, two types of IO₆-octahedral chains could be distinguished, the straight ones alternating with those which are somewhat twisted. This arrangement gives use to a pseudo-monoclinic symmetry, which becomes true if the crystals are heated to 72.5°C, the space group being Cm. At 212°C they transform to a rhombohedral modification possessing the space group R[unk].