The changes of exchange alkalinity and exchange acidity in the two types of red soil with the presence of three neutral salt solutions was controlled automatically equipment. It was found that in studied quantitatively by pH the solution of Na₂SO₄ the exchange alkalinity appeared at low pH, while exchange acidity at high pH. The amount of exchange alkalinity of latosol is larger than that of red soil. The exchange neutrality point which was not influenced by the concentration of Na₂SO₄ was nearby pH4.6.Only the exchange acidity appeared in the solutions of NaClO₄ and KClO₄ in the range of pH measured. The amount of exchange acidity was found more in the red soil than that in the latosol. For the same soil colloid the amount of exchange acidity in KClO₄ solution was greater than that in the NaClO₄ solution. The peak value of exchange acidity was shown at pH 4.3 in the solution of KClO₄ and at pH 5.8 in the solution of NaClO₄ for the latosol colloid.A method of measuring the SO₄^2-—exchange alkalinity was constructed.