The general procedure is as follows: take a proper amount of manganese ore (less than 200 mesh), add about 15ml phosphoric acid and about 0.5 ml nitric acid, heat to release phosphoric acid smoke, take down about 2g ammonium nitrate solid, blow out nitrogen oxides with ear washing ball, wait for a moment, add about 80ml water, cool to room temperature, and titrate with ferrous sulfate as indicator. . . . . . The calculation results are replaced by standard patterns with equivalent contents. . . .

This is for manganese, and there are other things, if necessary, you can contact in detail. .