AN EVALUATION OF 0.1  M PYROPHOSPHATE AND PYROPHOSPHATE-DITHIONITE IN COMPARISON WITH OXALATE AS EXTRACTANTS OF THE ACCUMULATION PRODUCTS IN PODZOLS AND SOME OTHER SOILS

Abstract

The 0.1 M Na-pyrophosphate solution extracted some of the Fe-, Al-organic matter products in Podzol B and some Acid Brown Wooded B horizons, but it dissolved a low proportion of the free Fe in the B horizon of some Gleysolic soils. It did not dissolve the inorganic amorphous or crystalline Fe and Al substances tested. The oxalate solution extracted Fe and Al from some amorphous inorganic substances as well as from horizons of accumulation or Fe-, Al-organic matter complexes, but it did not dissolve crystalline Fe oxides. The pyrophosphate-dithionite solution removed some Fe from crystalline oxides as well as from amorphous organic and inorganic forms.Although the pyrophosphate solution appeared to be the most specific for the sesquioxide-organic complex accumulation products in some soils, high speed centrifugation was necessary to obtain extracts free of suspended material. The oxalate procedure was simpler and it appeared to be equally useful for differentiating the classes of soils tested. The pyrophosphate-dithionite procedure appeared to be the least specific of the three.