Lanthanum sesquioxide, LaO₃

Lanthanum sesquioxide, or lanthana, La₂O₃, is obtained as a white powder by the ignition of the hydroxide, carbonate, nitrate, oxalate, etc. The strongly ignited oxide has a density of 6.53 at 17° (Cleve), 5.94 (Hermann). It is slightly diamagnetic; the specific heat between 0° and 100° is 0.0749. The powder rapidly absorbs water, with the evolution of heat, and it also combines readily with carbon dioxide. The oxide crystallises in the form of hexagonal bipyramids of density 5.30 when dissolved in borax at a white heat and slowly cooled; the crystals are not affected by water.

Lanthana, even after intense ignition, is readily soluble in acids.