Influence of the pH-Value on the Metastable Zone Width of Potassium Sulphate

Aqueous solution of the potassium sulphate with addition of sulphuric acid or potassium hydroxide has been chosen for the metastable zone width measurements in order to check how the solution structure affects the nucleation. Hydration analysis of corresponding sub-systems indicated involved structure changes. The solubility of K₂SO₄ increases with addition of H₂SO₄ and decreases with addition of KOH. The hydration analysis has shown that low acid concentrations have an inexpressive effect on the structure of solution. Much distinct effect exhibit low concentrations of the hydroxide. The metastable zone width decreases with increasing the value of pH. This decrease is less perceptible in the acidic region but more distinct in the alkaline region. The same holds for the critical nucleus size L* and the specific surface energy σ*. The behaviour quoted above supports the conception that the pH affects the solution structure and that the latter has a significant effect on the nucleation.