2. Soil potential acidity (1) Strong acidity in soil Colloid-A13+=Colloid+A13+ A3++3H2O Al(OH)3+ 3H (2) Acidity and weak acidity in soil Al(OH 2+ +HOH A1(OH)2++H+ Al(OH 2+ + HOH Al(OH)3++H+ Or: Colloid-H+—H2． Soil potential acidity (1) Strong acidity in soil Colloid-Al3+ = Colloid + Al3+ Al3+ + 3H2O Al（OH)3 + 3H+ (2) Acidity and weak acidity in soil Al（OH）2+ + HOH Al（OH）2+ + H+ Al（OH）2+ + HOH Al（OH）3+ + H+ Or: Colloid-H+ H+