What is Refining?
'''Refining''' is the name for a number of processes that purify or concentrate a substance. The name is used for [[natural resource]]s, [[food]] and technical products. The place where this is done, is often called a '''refinery'''. ==Petroleum== {{main|Oil refinery}} [[File:Oil refinery canada.jpg|thumb|An petroleum refinery]] [[Petroleum]] contains [[hydrocarbon]]s. After [[distillation]], it still contains [[chemical compound]]s with [[sulfur]], [[oxygen]] and [[Nitrogen]] as well as other unwanted compounds, such as [[Alkalene]]s. Processed petroleum is used for [[lubricant]]s; the substances mentione are unwanted in lubricants as they can speed up the aging process. For this reason, they are extracted using a process called [[hydrogenation]]. In hydrogenation, [[Hydrogen sulfide]] and [[ammonia]] [[gas]]es are produced. These gases require special handling, as they are very [[toxic]]. ==Vegetable oil== [[Vegetable oil]]s and fats are produced by chemical or mechanical extraction from [[plant]]s. This produces a kind of oil that still has many unwanted substances, such as [[pigment]]s and smell, which influence the quality of the refined product. In essence, the factors influenced are taste, [[shelf life]], smell and color, as well as the ability to use the oil for further technical transformations. Depending on the process, between four and eight percent of usable vegetable oil is lost. There are two basic procedures to refine vegetable oil, chemical refining, and physical refining. ==Sugar== [[Sugar]] is washed, and treated with concentrated [[syrup]]. Its colored because most customers expect sugar to be white. The white sugar sold in shops in almost pure [[sucrose]]. It has an extent of 99,8 percent of its weight. ==Metals== [[File:Lead electrolytic and 1cm3 cube.jpg|thumb|[[Lead]] after electrolytic refining. The cube shown is 1 cubic centimeter in size.]] There are two basic processes to refine [[metal]]s: Refining by fire, and refining by [[electrolysis]]. Higher grades of purity require both pro