“…Several studies of the analytical precipitation of magnesium ammonium phosphate and its subsequent treatment are summarized in the section on phosphorus (40,41,170). To determine magnesium in filtrates from calcium oxalate precipitation, by either the magnesium ammonium phosphate or the oxine (8-hydroxyquinoline) method, Holth (76) states that ammonium oxalate must first be removed, preferably by oxidation with bromine or by evaporation of the solution to dryness and heating over a free flame.…”