Yttrium sulphate, Y₂(SO₄)₃

The specific heat of the anhydrous Yttrium sulphate, Y₂(SO₄)₃, between 0° and 100° is 0.1319.

The system Y2(SO4)3 - Na2SO4 - H2O at 25° C. Solubility diagram.

The monoclinic octahydrate, Y₂(SO₄)₃.8H₂O, is the only hydrate known. At 25° the saturated solution contains 5.38 grams of anhydrous sulphate per 100 grams of water. Its solubility diminishes with rise of temperature.

The following double sulphates are known (Cleve): - Y₂(SO₄)₃.Na₂SO₄.2H₂O; Y₂(SO₄)₃.(NH₄)₂SO₄.9H₂O; 2Y₂(SO₄)₃.3K₂SO₄; Y₂(SO₄)₃.4K₂SO₄.

The addition of sodium sulphate increases the solubility of yttrium sulphate at first, and then causes the solubility to diminish rapidly. With diminution in solubility is associated a change in solid phase, from hydrated yttrium sulphate to double salt. Solutions supersaturated with respect to the double salt may remain in the metastable state for several months. The solubility curve for a temperature of 25° is shown in fig.