De-masking of magnesium—acetylacetonate complex for direct ethylenediaminetetraacetic acid titration of calcium and magnesium in the same solution and at the same pH

A simple complexometric method, with ethylenediaminetetraacetic acid as titrant, was developed for the determination of calcium and magnesium in a single aliquot of solution at pH ≈10. The method involves determination of calcium at pH ≈10, with use of a mixed indicator, after masking magnesium with acetylacetone at room temperature, followed by de-masking of magnesium at 90 °C and direct titration of magnesium at the same pH. The method was standardized against synthetic solutions and applied to various calcareous materials, and the results were compared with those obtained by a standard method.