What is Parts per million?
'''Parts per million''' is a [[Unit of measurement|unit]] which expresses a small [[Quantity|amount]] of dimensionless quantities. Proportionally, parts per million represents one thousandth of a [[Litre|millilitre]] of something per [[litre]] of [[water]], or one [[Gram|milligram]] of something per [[kilogram]] of [[soil]]. Just as per cent means out of a hundred, so parts per million or ppm means out of a million. Usually describes the concentration of something in water or soil. One ppm is equivalent to 0.001 milli-litre of something per litre of water (ml/l) or 1 milli-gram of something per kilogram soil (mg/kg). [[Category:Chemical nomenclature]] [[Category:Units of measurement]] {{stub}}