Electrolytes and their dissociation

By the theory of electrolytic dissociation an acid is a substance that gives only H⁺ as the cation, e.g. HNO₃ → H⁺ + NO₃⁻. Polybasic acids dissociate in steps: H₂SO₄ → H⁺ + HSO₄⁻, then HSO₄⁻ → H⁺ + SO₄²⁻, the second step being much harder than the first. A base (an alkali if soluble) gives only OH⁻ as the anion: NaOH → Na⁺ + OH⁻, Ca(OH)₂ → Ca²⁺ + 2OH⁻. A salt consists of a metal cation (or NH₄⁺) and an acid-residue anion; Al₂(SO₄)₃ → 2Al³⁺ + 3SO₄²⁻. An acid salt (NaHSO₄) first gives Na⁺ and HSO₄⁻, and HSO₄⁻ then gives H⁺ and SO₄²⁻. The general properties of acids (sour taste, colour change of indicators) are due to H⁺ and those of alkalis to OH⁻; salts have no common ion, so they have no common properties.