The acid leaching technique has been reported to produce gallium in which no impurities are detectable spectroscopically. Zone-refining, however, appears very effective in removing trace metallic impurities, but comparatively ineffective in removing the surface oxide film.
The low melting point and relatively high thermal conductivity of gallium introduce some difficulty in maintaining frozen and molten zones in zone-refining.
The only impurity found was lead, the following elements being reported also as checked but not found in the pure material: Al, Sb, As, Ba, Be, Bi, B, Cd, Ca, Cr, Co, Cb, Cu, Ge, Au, Fe, Mg, Mn, Mo, Ni, Pt, Si, Ag, Na, Sr, Sn, Te, Ti, W, V, Zn, and Zr.
