A process for making a yellow iron oxide pigment. Hydrated ferric oxide seed is added to a solution of ferrous sulfate and the suspension circulated over scrap iron, with air being passed through. Hydrated ferric oxide deposits on the seed crystals, giving a finely divided, yellow pigment: 4FeSO4 + 6H2O + O2 = 4FeO•OH + 4H2SO4. (Check source for accuracy of chemical formula)