Large molecular size organic substances that are present in most petroleum materials and in all heavy oils and bitumens. Asphaltenes are highly aromatic, have lower hydrogen content, and a higher content of sulfur, nitrogen, nickel, vanadium, and oxygen. They are rich in ring groups, not straight chains, with a size of ring groups ranging from 1-7 rings in a single cluster. Bridges between these clusters give larger molecules and extreme diversity of composition. This material is defined by solubility: soluble in aromatics and precipitate in C5 to C7 n-alkane solvents.