of the Universal Oil Products Company,29’ 30> 31 and is defined as the ratio of the cube root of the average boiling point (in degrees Rankine) to the specific gravity at 60°/60° F. For highly paraffinic crudes this factor is 12-5-13-0, while for aromatic or naphthenic crude-oil fractions its value is Crude oil contains organic compounds, heteroatom compounds (S,N,O), hydrocarbons (C, H), metals and organic (Ni, V, Fe) and inorganic (Na +, Ca ++, Cl-) compounds as listed in Figure 1.7. Compounds that contain only elements of carbon and hydrogen are called hydrocarbons and constitute the largest group of organic compounds found in petroleum. Petroleum or crude oil is a complex mixture of hydrocarbons and other chemicals. The composition varies widely depending on where and how the petroleum was formed. In fact, chemical analysis can be used to fingerprint the source of petroleum. However, raw petroleum or crude oil has characteristic properties and composition.