Manganese in Steel
Manganese in steel improves its hot working properties and increases strength, toughness and hardenability. Most steels contain up to 1% manganese.
The amount of manganese in steel can be determined by oxidising it to permanganate ion (MnO4-) and comparing the intensity of the purple colour with the colour of known permanganate solutions.
The method involves dissolving a sample of steel in nitric acid followed by the addition of phosphoric acid and potassium periodate (KIO4) which oxidises Mn2+ to MnO4-.
There are numerous published methods, for example see this link.
The graph below shows a calibration curve for potassium permanganate.