This metal occurs in minute proportions in some samples of zinc - blende. To separate it, the blende is dissolved in sulphuric or hydrochloric acid, or in aqua - regia, and the solution is decomposed by adding metallic zinc. The precipitate contains most of the foreign metals accompanying the zinc It is treated with hydrochloric acid, and again with zinc in the cold; as soon as the evolution of hydrogen becomes feeble, the solution is decanted, and saturated with sulphuretted hydrogen; the resulting precipitate is filtered off; the remaining solution is warmed, to drive off excess of sulphuretted hydrogen, and fractionally precipitated by sodium carbonate in the cold till the precipitate no longer give3 the gallium line in the spectroscope; the new precipitate is dissolved in sulphuric acid, slowly evaporated till the excess of acid is almost removed, and treated for some time with cold water; this solution is diluted, and heated to boiling, when basic gallium sulphate separates out; this is filtered off while hot, and dissolved in a little sulphuric acid; slightly acid solu tion of ammonium acetate is added, and sulphuretted hydrogen is passed through to saturation; the solution is filtered, diluted, and heated to boiling; the new precipitate is washed with boiling water, and dissolved in a little sulphuric acid; a slight excess of alkali is added, and the alkaline solution is electrolysed, when metallic gallium is deposited on the platinum pole.

To render it perfectly pure, it is treated with warm dilute nitric acid, free from chlorine. The metal possesses some curious properties. It fuses at 86° F. (30° C.) and then remains liquid for many weeks even at 32°F. (0° C), unless touched by a fragment of solid gallium, when it immediately crystallizes. The molten metal covers glass surfaces with a mirror - like coating, and oxidizes on exposure to the air. The solid metal has a sp. gr. of 5 . 9, and a blue - white colour; it is tough, and may be cut with a knife. It dissolves readily in caustic potash and dilute hydrochloric acid, and slowly in warm dilute nitric acid; but it is scarcely affected by cold dilute nitric acid, and is not volatile at a red heat.