Oil is the oily liquid dark red-brown, sometimes almost black, color. It includes about 1000 substances! The greatest part of them (80-90%) are hydrocarbons, i.e. organic matter composed of atoms of carbon and hydrogen. The oil contains about 500 hydrocarbon compounds - paraffins (alkanes), constituting half of all petroleum hydrocarbons, naphthenic (zilanov) and aromatic (benzene and its derivatives).
Available in oil and high-molecular compounds in the form of resins and asphaltic substances.
The total content of carbon and hydrogen in oil is about 97-98% (by weight), including carbon 83-87% and hydrogen 11-14%.
Depending on the number of atoms of carbon and hydrogen in the molecule hydrocarbons can be gases, liquids or solids. Hydrocarbons with the number of carbon atoms equal to 1-4, in normal conditions - gases. Hydrocarbons containing from 5 to 15 carbon atoms, liquids and hydrocarbons containing in the molecule more than 15 carbon atoms, - solid. Gaseous paraffin hydrocarbons (methane, ethane, propane and butane) are present in the oil in a dissolved state and when the output of oil on the surface stand out from it in the form of associated gas. Liquid paraffin hydrocarbons constitute the bulk liquid of the oil. Solid paraffin hydrocarbons dissolved in the oil can be separated from it.
In addition to the hydrocarbon part of the oil contains small non-hydrocarbon part of sulfur, nitrogen and oxygen. Sulfur in crude oil is pretty much up to 5%, and it brings a lot of troubles for the oil, causing corrosion of metals.
In small amounts in the oils meet vanadium, Nickel, iron, aluminum, copper, magnesium, barium, strontium, manganese, chromium, cobalt, molybdenum, boron, arsenic, potassium and other chemical elements.