Refining (also called affining) is the process of purification of a (1) substance or a (2) form. 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 by-products. The term is broad, and may include more drastic transformations, such as the reduction of ore to metal (for which see Refining (metallurgy)).
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 favor 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 depends on precise control of impurities. The zone melting process developed by William Gardner Pfann was used to produce pure germanium, and subsequently float-zone silicon became available when Henry Theuerer of Bell Labs adapted Pfann's method to silicon.
Types of materials that are usually refined:
- metals - see Refining (metallurgy)
- petroleum
- silicon
- sugar
- table salt
- vegetable oil
Famous quotes containing the word refining:
“Involuntary mental hospitalization is like slavery. Refining the standards for commitment is like prettifying the slave plantations. The problem is not how to improve commitment, but how to abolish it.”
—Thomas Szasz (b. 1920)
“The Americans ... are almost ignorant of the art of music, one of the most elevating, innocent and refining of human tastes, whose influence on the habits and morals of a people is of the most beneficial tendency.”
—James Fenimore Cooper (1789–1851)
“Artistic growth is, more than it is anything else, a refining of the sense of truthfulness. The stupid believe that to be truthful is easy; only the artist, the great artist, knows how difficult it is.”
—Willa Cather (1876–1947)