Not applicable in the presence of metaphosphate. The presence of pyrophosphate at normal concentrations Ämaximum 6 % (m/m)Ü does not interfere. The principle consists in precipitation of tripolyphosphate as its complex with tris(ethylenediamine) cobalt(III) chloride at a pH of between 3 and 4 in a buffered medium. Filtration, washing, drying and weighing of the precipitate. Details the preparation of the reagent used for analysis. Has also been approved by the IUPAC.