Thermal methods of determination of potassium and ammonium in milligram amounts by decomposition of nitritocobaltates(III) of the sodium group

The method of determination of milligram amounts of potassium and ammonium has been worked out. It consists in thermal decomposition of potassium-sodium and ammonium-sodium nitritocobaltates(III) at 300 °C. Nitrogen oxides issued during the decomposition are absorbed in the solution of KMnO₄ and determined by oxidimetric method. The method presented has been applied for determination of potassium and ammonium in the biological material (serum, section of muscle, urine). The method allows determination of potassium and ammonium (based on the mass of the precipitate of nitritocobaltates(III) and amount of nitrogen oxides being issued) with no need for their separation.