Defines a titrimetric method for the determination of the phosphorus content of iron ores, using hexaammonium heptamolybdate (ammonium molybdate). Applies to a concentration range of 0,10% (m/m) to 5,0% (m/m) of phosphorus in natural iron ores, and iron ore concentrates and agglomerates including sinter products. It also provides a quality control method for the determination of phosphorus by titration method, however the method cannot be used for referee purposes.