Chemical properties of Gallium

Gallium is only superficially oxidised when heated, even to redness, in air or oxygen. It does not decompose water at 100°, and under air-free water it remains bright and unaffected for a long time. It dissolves slowly in mineral acids. Solid gallium dissolves much faster in hydrochloric acid than does the liquid metal. Warm nitric acid dissolves it slowly, and the best acid solvent is aqua regia. Gallium dissolves in potassium hydroxide, with the liberation of hydrogen. It unites directly with chlorine, bromine, and iodine, in decreasing order of activity.

Gallium forms two classes of compounds, of the types GaX₃ and GaX₂ (X denoting a univalent acid radicle). The latter closely resemble the compounds of aluminium. Concerning the former, which instantly reduce potassium permanganate in dilute acid solution, very little is known.