Note 356 — Chapter X · ALUMINIUM; AMPHOTERIC HYDROXIDES; HYDROLYSIS OF SALTS. THE ALUMINIUM AND ZINC GROUPS

The displacement of hydrogen by a metal, like sodium, is the result of the displacement of the hydrogen-ion (see Chapters XIV and XV). The hydrogen-ion in fused sodium hydroxide is probably formed chiefly by the secondary ionization of the hydroxide-ion (HO− ⇄ H+ + O2−) (see Chap. XIII). We cannot have positive ions, Na+, with negative ions, O2−, without having some ions NaO−. (O2− + Na+ ⥂ NaO−), NaOH, undoubtedly, is much too weak an acid to form salts with bases in the presence of water. Such salts would be decomposed by water (see below, p. 180), as sodium oxide, indeed, is decomposed; we have Na─O─Na + HOH ⇄ 2 NaOH (see Chapter XIII for a detailed discussion of this action). These relations sufficiently account for the fact that salts of sodium hydroxide, in which it has the functions of an acid, are not commonly formed. (Cf. Abegg, Anorganische Chemie, II, (1) p. 247.)