Rapid determination of magnesium in the presence of calcium and phosphate by titration with cdta

A method is presented for the accurate determination of magnesium in phosphate rock and phosphoric acid down to 0.03% magnesium oxide in the presence of 0–70% phosphorus pentoxide by titration with cyclohexanediaminetetraacetic acid (CDTA). Interference from heavy metals for which inaccurate empirical corrections have previously been made in the combined magnesium and calcium titration are linearly and unequivocally determined and subtracted from the combined titration. Magnesium oxide is determined in less than 20 min after sample digestion for Ca: Mg ratios from 1:9 to 850:1.