A crystalline organic compound, which produces the color of electrolytic caustic, has been isolated from a water extract of old graphite stubs. This compound has an empirical formula of , and seems to be pyromellitic acid‐chloroquinone. It is a very stable compound not destroyed by aqua regia or nitro‐sulfuric acids. It can be decomposed in steps by fusion with to give a residue of phenols, and . It is probably a product of oxidation of the graphite anode.