Manganese in steel can be determined by using colorimetry because the manganese can be converted into permanganate ions which are coloured. The conversion is achieved in two stages. Using nitric acid, the manganese is first oxidised to manganese(II) ions which are then oxidised to permanganate ions by the more powerful oxidising agent, potassium periodate.
Manganese in steel – pupil guide
Manganese in steel – Teacher’s guide
Manganese in steel – Risk assessment