Potash alum, the ratio of \( \text{K}^+ \) and \( \text{SO}_4^{2-} \) ions is

Potash alum has the formula \( \text{K}_2\text{SO}_4\cdot\text{Al}_2(\text{SO}_4)_3\cdot24\text{H}_2\text{O} \). It furnishes 2 \( \text{K}^+ \) ions and 4 \( \text{SO}_4^{2-} \) ions per formula unit, giving a ratio of 2:4 which simplifies to 1:2.