The lecturer in the Department of Chemical Engineering and Petroleum Industries wrote a scientific article entitled (Oil Refining). The content of the article was:<br />Crude oil is a very complex mixture that varies greatly from one region to another, and from one oil field to another. Each has a special individual composition and cannot be exactly the same as any crude oil. They differ from each other in physical and chemical properties. Some crude oil comes in a mobile liquid form. One is light in color and the other is dense or contains tarry substances, and they also differ in smell. Oil is in underground reservoirs in rocky structures, and is extracted from these machines by drilling wells under reservoir pressure or by external pumping. Hydrocarbon compounds are the main compound in crude oil, or they are substituted hydrocarbons, which contain two main components: Carbon (87-83%) and hydrogen (10-14%) are combined with three other less important elements: sulfur (0.1-3%) and rarely 7%, and nitrogen (0.1- 2%) and oxygen may reach up to 1.5%. Petroleum is subjected to various refining processes that include physical processes (distillation, stabilization of diluted distillates, purification) and chemical processes (cracking, reformation).