4. Reagents and materials ... 4.8. Reagent for phosphate determination: dissolve 20 g of ammonium molybdate (CAS 12054-85-2), ... in 400 ml water at 50°C; dissolve, in another vessel, 1 g of ammonium vanadate (CAS 7803-55-6), NH4VO3, in 300 ml hot water, allow to cool, then add 140 ml of concentrated nitric acid (CAS 7697-37-2). Combine the cooled solutions in a 1000 ml volumetric flask and make up to the 1000 ml mark.
