DETERMINATION OF SILICON, ALUMINUM AND IRON DISSOLVED BY SUCCESSIVE AND SELECTIVE DISSOLUTION TREATMENTS OF VOLCANIC ASH SOIL CLAYS

Abstract

Si, Al and Fe extracted from volcanic ash soil clays by the treatments with Na₂S₂O₄-NaHCO₃-Nacitrate, 2% Na₂CO₃ and 0.5N NaOH were determined. A procedure was developed for the simultaneous determination of Al and Fe by ferron after the removal of citrate from these extracts by wet oxidation using H₂SO₄ and H₂O₂. The percentage recovery of Si added to the respective extracts of volcanic ash soil clays was in the range 99±2, while that of Al 97±3. In the proposed procedure, the recovery of Al added to each sample solution was tested and used for correction.
The weight loss of the clay by each dissolution treatment and the sum of the amounts of then extracted SiO₂, Al₂O₃ and Fe₂O₃ were compared. These values were evaluated from the point of view of semiquantitative mineralogical analysis of volcanic ash soil clays.