Gram per litre
A gram per litre or gram per liter is a unit of measurement of mass concentration that shows how many grams of a certain substance are present in one litre of a mixture. It is not an SI unit – the SI unit of mass concentration is kilogram per cubic metre, which is equivalent.
Metric prefixes are often applied, giving units like milligrams per litre or micrograms per decilitre. When measuring concentration in water, parts per million is an older expression of mg/L, since one litre of water under standard conditions weighs one kilogram.
Milligrams per litre are often used in medicine and in medical prescriptions. For example, a description of a solution that involves two substances, where one of the substances involves adding water, would state: "10 mg/L water and substance". Blood sugar concentration is sometimes measured in milligrams per decilitre.
