Gallium (Ga) is the third element in Group IIIA in the periodic table. It has an atomic number of 31, an atomic weight of 67.72, and valences of 1, 2, and 3. The average abundance of Ga in the earth’s crust is 19 ppm; in soils it is 1.9 to 29 ppm; in streams it is 0.09 μg/L; and in groundwaters it is <0.1 mg/L. Gallium occurs in many zinc ores, and nearly always in bauxite. Gallium compounds are used in semiconducting devices.
The element exists as Ga3+ in natural water, and its solubility is controlled by formation of the hydroxide. It is considered nonessential for plants and animals.
Perform analyses by the electrothermal atomic absorption method (Section 3113 B). The inductively coupled plasma/mass spectrometric method (Section 3125) also may be applied successfully in most cases (with lower detection levels), even though gallium is not specifically listed as an analyte in the method.