Blocked Charges on Clay Minerals in Sub‐tropical Soils

Summary Hypothetical mechanisms for charge blocking on the surfaces of kaolinitic minerals are presented to account for the anomalous behaviour of ferrallitic soils on deferrification. On iron oxide removal, the following situations can arise where positive and negative charges (i) both increase, or (ii) both decrease, or (iii) increase and decrease concomitantly. These variations in charge after deferrification can adequately be explained on the basis of blocking which affects both the basal planes and edges of the clay minerals.