It is best to start with electrolytic iron sheet; this is held over benzene vapor to deposit a layer of carbon, then baked for a long time in vacuum at 700°C and slowly cooled. To isolate Fe3C the sheet is placed in a neutral FeCls bath and used as an anode at the lowest possible current density. The bath is the same as used in the preparation of electrolytic iron. In this way very pure Fe3 C is left behind as a coarsely crystalline gray powder. It is washed with dilute acetic acid, water, alcohol and ether, and dried in vacuum.
