Iron stains can be removed from most washable fabrics with oxalic acid, provided certain precautions are taken. Oxalic acid can be obtained at most drug stores.
A solution of the oxalic acid may be made up by simply dissolving the crystals in water. The solubility of the acid is only about 10% so, it cannot be made too strong. The solution should be prepared in an enamelled or plastic container, never in a bare metal pail.
A small amount of the solution should be tried on the inside of a hem or other inconspicuous location as the acid may bleach certain dyes. If, it is apparent that no bleaching has occurred, the entire garment may be repeatedly dipped in the solution. The dipping should continue until the iron stains are gone. Allowing the garment to soak in the acid solution is not recommended.
After the stains have disappeared, the garment should be thoroughly rinsed in several changes of fresh water. To be sure that any remaining acid has been neutralized, the garment should be immediately laundered in the normal manner with the regular amount of soap. The alkalinity in the soap will eliminate the last traces of acidity.
The acid solution may be poured down the drain but it should be followed with a thorough flushing with fresh water.