I am making ferric oxide (Fe2O3) for a school project. I have immersed a piece of iron in a solution of tap water and salt (to allow for electrical conductivity). The piece of iron in attached to the positive terminal of a battery charger and the negative wire is attached to a section of graphite from a pencil. When i plug in the charger, the negative wire starts bubbling and after a while, a blueish-green substance begins to form at the bottom of the container and on the piece of iron. What is this substance bluish-green? How do i correct my procedure to obtain rust?