Gadolinium(III) Oxide (archaically Gadolinia) is an inorganic compound with the formula Gd2O3, which is the most available form of the pure gadolinium and the oxide form of one of the rare earth metal gadolinium. Gadolinium oxide is also known as gadolinium sesquioxide, gadolinium trioxide and Gadolinia. The color of the gadolinium oxide is white. Gadolinium oxide is odorless, not soluble in water, but soluble in acids.