Gallium, the eka-aluminium of Mendeleeff, is a hard, brittle, grey metal having a greenish-blue reflex. It melts at the remarkably low temperature of 30.15° C. to a silver-white liquid which is only slightly volatile even at a red heat. In the absence of the solid phase, liquid gallium possesses to an extraordinary degree the property of remaining in a super- fused state. The metal crystallises with great readiness in the tetragonal (or possibly the monoclinic) system, the crystals possessing an octahedral habit and usually possessing slightly convex faces. The density of the solid is 5.96 at 24.5°; that of the liquid is 6.07 at 24.7°. Gallium, therefore, like water, expands on freezing. The mean specific heat, of the solid metal is 0.079 between 12° and 23°; that of the liquid is 0.0802 between 106° and 119°. The latent heat of fusion is 19.03 calories per gram of metal. The specific resistance exceeds that of the alkali metals. Liquid gallium is electronegative to the solid element. The atomic refraction of gallium in its compounds is 14.8 (for the Hα line; Gladstone and Dale's formula). Gallium is diamagnetic.
The spark spectrum of gallium is characterised by two violet lines, λ4172.2 and λ4033.2, the former being the more intense. |