Single reagent method for the spectrophotometric determination of phosphorus in silicates

Abstract

A method has been developed for the spectrophotometric determination of phosphorus in silicate rocks following fusion with a lithium borate flux and dissolution of the melt in dilute nitric acid. By using a single reagent incorporating antimony and relatively high concentrations of ascorbic acid and hydroxylammonium chloride, a stable colour has been achieved. The colour is fully developed within 30 min and is stable for up to 4 h in solutions containing up to 0.8 µg ml^–1 of phosphorus(V) oxide with nitric acid concentrations not greater than 0.04 N. Beer's law is obeyed and ε= 22200 at 880 nm.