ABSTRACT
pH is a measure of hydrogen ion concentration in an aqueous solution. pH measurements are affected by temperature and the presence of very high concentrations of suspended matter. Soil pH is determined by mixing the soil with reagent grade water, stirring the solution, allowing the soil to settle down, and then recording the pH of the supernatant liquid. The chemical reactions in the aqueous system depend on both the pH and the Eh. While pH measures the activity (or concentration) of hydrogen ions in the solution, Eh is a measure of the activity of all dissolved species. Aqueous solutions contain both oxidized and reduced species. The oxidation–reduction potential is sensitive to pH. The Eh decreases with an increase in the pH and increases with a decrease in the pH, if H+ ion or OH- ion is involved in the redox half-cells.
