Edta Dissolution of Gypsum, Anhydrite, and Ca-Mg Carbonates

ABSTRACT Removal of sulfate and carbonate minerals from clay assemblages can be accomplished using boiling EDTA (ethylenedinitrilotetraacetic acid) at pH 10-12 as a solvent. This procedure avoids the danger of altering or destroying some clay species when conventional acid dissolution techniques are used. Solubilities of 19g/l magnesite, 21g/l dolomite, 23g/1 calcite, 34g/1 anhydrite, and 43g/1 gypsum of 0.25 M EDTA solution at pH 11 were determined by titration of the solvent. Apatite solubility is low (about 1g/l) and fluorite is essentially insoluble. Alteration of kaolinite, montmorillonite, illite, and chlorite appears to be minimal as determined from preliminary comparative X-ray diffraction studies.