impureté

Traductions

• anglais

  Date : 1983

  Définition

  An extremely low percentage of an extraneous substance either naturally present in a material or added to it accidentally or intentionally.

  Notes :

  Often it is impossible to completely eliminate naturally occurring impurities by any separation method, but there are many processes that are effective in reducing them to an acceptable minimum. So small are the amounts involved that impurities are usually indicated in parts per million (ppm). Common examples are calcium carbonate in hard water, strontium-90 in milk, mercury compounds in fish, and insecticide residues in foods.
  
  Or special importance is the fact that not all impurities areundesirable; their presence may have a beneficial effect, and they are often added intentionally. Examples are (1) arsenic or boron in semiconductors, (2) carbon in iron or steel, (3) doping agents in laser crystals, and (4) fluoride in drinking water.

  Terme :

  1. impurity