Oxygen/nitrogen mixtures liquid properties

S mixture is a combination of two or more substances in which each substance retains its properties. Most materials we encounter are mixtures mixtures of elements, mixtures of compounds, or mixtures of elements and compounds. Stainless steel, for example, is a mixture of the elements iron, chromium, nickel, and carbon. Seltzer water is a mixture of the liquid compound water and the gaseous compound carbon dioxide. Our atmosphere, as Figure 2.14 illustrates, is a mixture of the elements nitrogen, oxygen, and argon plus small amounts of such compounds as carbon dioxide and water vapor. 

Finally, the properties of air, whether in the gaseous or liquid phase, are intermediate between those of oxygen and nitrogen respectively, thereby suggesting a mixture, for, as a general rule, compounds do not resemble their components either physically or chemically. 

Petroleum is a naturally occurring mixture of hydrocarbons, generally in a liquid state, that may also include compounds of sulfur, nitrogen, oxygen, metals, and other elements (ASTM D-4175). Consequently, it is not surprising that petroleum can vary in composition properties and produce wide variations in refining behavior as well as product properties. 

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