A potassium chloride solution (1M KCl) is used in this method, with pH determined under conditions similar to those for 0.01 M CaCl2. This method is used in conjunction with Method 4A1 for the estimation of Δ pH (see Section 4F1). Accordingly, it is particularly applicable to acidic, highly weathered soils dominated by colloids with variable surface charge characteristics.
1.0 M Potassium Chloride
Dissolve 74.55 g potassium chloride (KCl) and make to 1.0 L with deionised water.
pH Buffer Solutions
pH buffer solutions are as described for Method 4A1.
Standardise the pH meter as described in Method 4A1.
Proceed as for Method 4B1 except use 1 M KCl when preparing suspension. Complete all measurements on the same day, ideally within 4 h.
Report pH (1:5 soil/1 M KCl) on an air-dry basis; abbreviate as pHKCl.