Science Fair Project Encyclopedia
Refining is the process of purification of a substance, usually used of a natural resource that is almost in a usable form, but which is more useful in its pure form. For instance, most types of natural petroleum will burn straight from the ground, but it will burn poorly and quickly clog an engine with residues and byproducts. The term is broad, and may include more drastic transformations, such as the reduction of ore to metal.
The refining of liquids is often accomplished by distillation or fractionation. Gases can be refined this way as well, by being cooled and/or compressed until they liquefy. Gases and liquids can also be refined by extraction with a selective solvent that dissolves away either the substance of interest, or the unwanted impurities.
Chemical reactions are often used to remove impurities of particular types.
Types of materials that are usually refined:
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