STUDIES ON PYRIMIDINE-DERIVATIVES .16. SPECTROPHOTOMETRIC DETERMINATION OF COBALT(III) WITH 2-DIETHYL-AMINO-5-NITROSO-1,4,5,6-TETRAHYDROPYRIMIDINE-4,6-DIONE

A simple method has been developed for the determination of cobalt. The cobalt(III) complex of 2-diethylamino-5-nitroso-1,4,5,6-tetrahydropyrimidine-4,6-dione (ENPD) is soluble in water and its yellow complex, once formed, is stable even at pH 1.0, while other metal complexes decompose at this pH. The cobalt(III)-ENPD complex has a molar absorptivity of 6.3x10(4) l mol-1 cm-1 at 385 nm. The formation of the complex is quantitative over the pH range from 4.8 to 6.8. The molar ratio of cobalt(III) to ENPD in the complex is 1:3 according to the continuous variation method. The proposed method was satisfactorily applied to the determination of cobalt in various samples, such as monel, nimonic and magnet alloys.