Praseodymium(III) sulfate is a praseodymium compound with formula Pr2(SO4)3. It is an odourless whitish-green crystalline salt. The anhydrous substance readily absorbs water forming pentahydrate and octahydrate.[1]
Properties
Praseodymium sulfate is stable under standard conditions. At elevated temperatures, it gradually loses water and becomes more whitish. Like all rare earth sulfates, its solubility decreases with temperature, a property once used to separate it from other, non-rare earth compounds.
Pentahydrate and octahydrate have monoclinic crystal structures with densities of 3.713 and 2.813 g/cm3, respectively. The octahydrate crystals are optically biaxial, with refractive index components of nα = 1.5399, nβ = 1.5494 and nγ = 1.5607.[1] They belong to the space group C12/c1 (No. 15) and have lattice constants a = 1370.0(2) pm, b = 686.1(1) pm, c = 1845.3(2) pm, β = 102.80(1)° and Z = 4.[3]
Synthesis
Crystals of octahydrate can be grown from solution obtained by dissolving wet Pr2O3 powder with sulfuric acid. This procedure can be optimised by adding a few evaporation/dissolution steps involving organic chemicals.[3]