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Yttrium(III) sulfate octahydrate, with the chemical formula Y2(SO4)3-8H2O, consists of infinite layers parallel to (10\overline 1), with [Y(H2O)4(SO4)3/2] being the only repeating unit. The layers are connected to each other using only moderately strong hydrogen bonds. The trivalent yttrium cation is coordinated by eight O-atoms from four sulfate groups and four water molecules in a distorted square antitetrahedron [YO8]. It is of the same structural type as the rare earth sulfate octahydrate^[1].

Figure 1. View perpendicular to the (10 1) layer of the title compound, with [Y(H 2 O) 4/1 (SO 4 (1)) 3/3 (SO 4 (2)) 1/2 ] as the repeat unit. Key: [SO 4 ] tetrahedra (yellow), [YO 8 ] antiprisms (red), oxygen (blue) and hydrogen (light grey) atoms.

Small, reddish-white, monosymmetric crystals. D 2.558, loses 8H2O at 120C, decomposes 700C. Soluble in concentrated sulfuric acid; sparingly soluble in water; insoluble in alkalies.

Red monoclinic crystals; density 2.59 g/cm³; loses all its water molecules at 120°C; decomposes at 700°C; sparingly soluble in water, less soluble in hot water; dissolves in concentrated sulfuric acid forming Y(HSO4)3; insoluble in alkalis; forms double salts with alkali sulfates.

Yttrium sulfate is produced as an intermediate in recovering yttrium from monazite or xenotime (see Yttrium, Recovery). Rare earth sulfates are separated on a cation exchange resin bed. Yttrium fraction is purified by fractional crystallization. Alternatively, yttrium sulfate may be prepared by reacting yttrium oxide with sulfuric acid.

[1] PETER HELD; Ma-thias W. Yttrium(III) sulfate octahydrate[J]. Acta crystallographica. Section E, Structure reports online, 2004. DOI:10.1107/S1600536803012182.