Selective Extraction of Amorphous Iron Oxides by Edta From a Danish Sandy Loam

Summary EDTA extracts (pH 7.5–10.5) from a Danish sandy loam showed no significant (95% level) increase in amounts of aluminium, calcium, iron, and magnesium between three and nine months' shaking. The amounts were independent of the soil: solution ratio (1:10–1:50), the EDTA concentration (0.01 M–0.2 M), and crushing the soil (< 0.25 mm or < 2 mm). IR spectroscopy and X‐ray diffraction showed no change in the mineral composition of the soil during the extraction. The extracted iron was equal to that extracted after 2 h by ammonium oxalate at pH 3.0. EDTA extraction at pH > 7.5 seems to extract selectively iron oxides with solubility products > ∼ 10 −41 .