ABSTRACT
The highest oxidation state of gallium (Ga), indium (In), and thallium (Tl) is +3. These elements may also exist in lower oxidation states, but gallium and indium are less stable in these states than in the +3 state, whereas thallium is considerably more stable in the +1 state. Furthermore, the chemical properties of Tl(III) are not similar to those of aluminium(III) (Al(III)), whereas those of Ga(III) and In(III) are very close to Al(III) in many respects. Hydroxides of Ga(III) and In(III) as well as Al(OH)3 are amphotheric; their salts are partly hydrolyzed. Gallium, indium, and thallium differ from Al in lower enthalpies of formation of their oxides and in the ease of their reduction to the metallic state. In basic solutions gallium may exist in the +1 state due to the low rate of its oxidation to Ga(III). Gallium dichloride is formed by treating a concentrated aqueous solution of GaCl3 with the metal. Upon dilution this solution evolves hydrogen.
