The Effect of Treatment with Hydrogen Peroxide and the Mehra–Jackson Reagent on X-ray Diffraction Patterns of Clay Fractions

Resumo

X-ray diffraction patterns of clay fractions from the AEL and EL horizons of pale-podzolic soil before and after treatment with 10% H₂O₂ and the Mehra–Jackson reagent in different sequences have been examined. The successive treatment with 10% H₂O₂ and then with the Mehra–Jackson reagent causes dissolution of Al-hydroxy-interlayers in pedogenic chlorites and the respective increase in the content of labile minerals because of a dramatic decrease in pH upon the treatment with hydrogen peroxide. The rate of these changes depends on the degree of chloritization of pedogenic chlorites in the initial samples. The result of the reverse sequence of the treatments of clay fractions (initially with the Mehra–Jackson reagent and then with hydrogen peroxide) is opposite: the chloritization of labile minerals becomes more intensive. It is provided by pH values that do not drop below 7.5 at any treatment stage. At particular stages, pH values favors the mobilization of Al compounds and their subsequent polymerization in the interlayer space of labile structures. We suppose that hydroxyl-aluminosilicate layers may be formed in the interlayer space upon this treatment sequence.