Praseodymium sulfate is a Pr compound with formula Pr₂(SO₄)₃. It is an odourless whitish-green crystalline compound. The anhydrous substance readily absorbs water forming pentahydrate and octahydrate.

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 n_α = 1.5399, n_β = 1.5494 and n_γ = 1.5607. They belong to the space group

Space group

In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...

 C12/c1 (No. 15) and have lattice constants a = 13.700(2) Å, b = 6.861(1) Å, c = 18.453(2) Å, β = 102.80(1)° and Z = 4.

Synthesis

Crystals of octahydrate can be grown from solution obtained by dissolving wet Pr₂O₃ powder with sulfuric acid

Sulfuric acid

Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

. This procedure can be optimised by adding a few evaporation/dissolution steps involving organic chemicals.