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Refining

2007 Schools Wikipedia Selection. Related subjects: Business

   Refining is the process of purification of a substance. The term is
   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 in 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.

   Many solids can be refined by growing crystals in a solution of the
   impure material; the regular structure of the crystal tends to favour
   the desired material and exclude other kinds of particles.

   Chemical reactions are often used to remove impurities of particular
   types.

   The use of silicon and other semiconductors in electronics is highly
   dependent on precise control of impurities, and a number of special
   techniques have been developed, such as zone refining.

   Types of materials that are usually refined:
     * metals
     * petroleum
     * silicon
     * sugar
     * vegetable oil

   Retrieved from " http://en.wikipedia.org/wiki/Refining"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
