Ammonium molybdate reacts with phospat ions to form phosphomolybdic acid which is reduced to molybdenum blue. (Reaction basis according to DIN EN ISO 6878-D11)

The phosphate content in a surface water has direct consequences for its ability to support the growth of certain organisms. Since ever increasing quantities of phosphates are being fed through domestic waste waters into rivers and lakes, these waters have a tendency towards eutrophication. Exact data about the phosphate content are important for boiler water and feed water. Precise dosing of phosphates in these waters can inhibit formation of boiler scale. Pyro-, meta- and polyphosphates are not determined with VISOCOLOR® test kits. The determination of total phosphate requires a decomposition prior to the test.