Litre
From Wikipedia, the free encyclopedia
The litre or liter (see spelling differences) is a unit of volume. There are two official symbols, namely the Latin letter el both in lower and upper case: l and L. The majuscle has been introduced in many english-speaking countries to avoid confusions with the numeral 1. The litre appears in several versions of the metric system; althouth not an SI unit, it is accepted for use with the SI. The international unit of volume is the cubic metre (m³).
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[edit] Definition
A litre is defined as a special name for a cubic decimetre (1 L = 1 dm³).
- 1 L = 0.001 m³ (exactly)
The original metric system used litre as a base unit.
[edit] SI prefixes applied to the litre
The litre may be used with any SI prefix.
| Multiple | Name | Symbols | Multiple | Name | Symbols | |||
|---|---|---|---|---|---|---|---|---|
| 100 | litre | l | L | |||||
| 101 | decalitre | dal | daL | 10–1 | decilitre | dl | dL | |
| 102 | hectolitre | hl | hL | 10–2 | centilitre | cl | cL | |
| 103 | kilolitre | kl | kL | 10–3 | millilitre | ml | mL | |
| 106 | megalitre | Ml | ML | 10–6 | microlitre | µl | µL | |
| 109 | gigalitre | Gl | GL | 10–9 | nanolitre | nl | nL | |
| 1012 | teralitre | Tl | TL | 10–12 | picolitre | pl | pL | |
| 1015 | petalitre | Pl | PL | 10–15 | femtolitre | fl | fL | |
| 1018 | exalitre | El | EL | 10–18 | attolitre | al | aL | |
| 1021 | zettalitre | Zl | ZL | 10–21 | zeptolitre | zl | zL | |
| 1024 | yottalitre | Yl | YL | 10–24 | yoctolitre | yl | yL | |
[edit] Name origin
The word "litre" is derived from an older French unit, the litron, whose name came from Greek via Latin.
[edit] Other volume equivalencies
- 1 TL (teralitre) = 1 km³
- 1 kL (kilolitre) = 1 m³
- 1 L (litre) = 1 dm³
- 1 mL (millilitre) = 1 cm³
- 1 µL (microlitre) = 1 mm³
[edit] Conversions
One litre
- ≈ 0.87987699 Imperial quart
- Inverse: One Imperial quart ≡ 1.1365225 litre
- ≈ 1.056688 US fluid quart
- Inverse: One US fluid quart ≡ 0.946352946 litre
- ≈ 1.75975326 Imperial pint
- Inverse: One Imperial pint ≡ 0.56826125 litre
- ≈ 2.11337641 US fluid pints
- Inverse: One US fluid pint ≡ 0.473176473 litre
- ≈ 0.2641720523 US liquid gallon
- Inverse: One US liquid gallon ≡ 3.785411784 litres
- ≈ 0.21997 Imperial gallon
- Inverse: One Imperial gallon ≡ 4.54609 litres
- ≈ 0.0353146667 cubic foot
- Inverse: One cubic foot ≡ 28.316846592 litres
[edit] Rough conversions
A litre is the volume of a cube with sides of 10 cm, which is slightly less than a cube of sides 4 inches (or one-third of a foot). Twenty-seven cubes "one-third of a foot on each side" would fit in one cubic foot, which is within 5% of the actual value of exactly 28.316846592 litres.
One litre is also slightly more than U.S. liquid quart and slightly less than one Imperial quart or the less common U.S. dry quart.
[edit] Explanation
Litres are most commonly used for items measured by the capacity or size of their container (such as fluids and berries), whereas cubic metres (and derived units) are most commonly used for items measured either by their dimensions or their displacements. The litre is often also used in some calculated measurements, such as density (kg/L), allowing an easy comparison with the density of water.
One litre of water has a mass of almost exactly one kilogram (1 litre of chemically pure water has a mass of 1 kg at 277.13 K (3.98 °C or 39.164 °F), at which point the pure water occupies the minimum volume per mas). Similarly: 1 millilitre of water has about 1 g of mass; 1000 litres of water has about 1000 kg (1 tonne) of mass. This relationship is because the gram was originally defined as the mass of 1 mL of water. However, this definition was abandoned in 1964 because the density of water changes with pressure and the units of pressure are dependent on the definition of mass.
[edit] Symbol
Originally, the only symbol for the litre was l (lowercase letter l), following the SI convention that only those unit symbols that abbreviate the name of a person start with a capital letter.
In many English-speaking countries, the most common shape of a handwritten Arabic digit 1 is just a vertical stroke, that is it lacks the upstroke added in many other cultures. Therefore, the digit 1 may easily be confused with the letter l. On some typewriters, particularly older ones, the unshifted L key had to be used to type the numeral 1. Further, even in some computer typefaces, the two characters are barely distinguishable at all. This caused some concern, especially in the medical community. As a result, L (uppercase letter L) was accepted as an alternative symbol for litre in 1979. The United States National Institute of Standards and Technology now recommends the use of the uppercase letter L, a practice that is also widely followed in Canada and Australia. In these countries, the symbol L is also used with prefixes, as in mL and µL, instead of the traditional ml and µl used in Europe. In Britain and Ireland, lowercase l is used with prefixes, though whole litres are often written in full (so, "750 ml" on a wine bottle, but often "1 litre" on a juice carton).
Prior to 1979, the symbol ℓ (script small l, U+2113), came into common use in some countries; for example, it was recommended by South African Bureau of Standards publication M33 in the 1970s. This symbol can still be encountered occasionally in some English-speaking countries, but it is not used in most countries and not officially recognised by the BIPM, the International Organization for Standardization, or any national standards body.
[edit] History
In 1795, the litre was introduced in France as one of the new "Republican Measures", and defined as one cubic decimetre.
In 1879, the CIPM adopted the definition of the litre, and the symbol l (lowercase letter l).
In 1901, at the 3rd CGPM conference, the litre was redefined as the space occupied by 1 kg of pure water at the temperature of its maximum density (3.98 °C) under a pressure of 1 atm. This made the litre equal to about 1.000 028 dm³ (earlier reference works usually put it at 1.000 027 dm³).
In 1964, at the 12th CGPM conference, the original definition was reverted to, and thus the litre was once again defined in exact relation to the metre, as another name for the cubic decimetre, that is, exactly 1 dm³. [1]
In 1979, at the 16th CGPM conference, the alternative symbol L (uppercase letter L) was adopted. It also expressed a preference that in the future only one of these two symbols should be retained, but in 1990 said it was still too early to do so.[2]
[edit] Colloquial usage
In spoken English, the abbreviation "mL" (for millilitre) is often pronounced as "mil", which is homophonous with the term "mil", meaning "one thousandth of an inch". This generally does not create confusion, because the context is usually sufficient — one being a volume, the other a linear measurement. In Australia and the UK "one thousandth of an inch" is commonly called a thou (soft th).
The colloquial use of "mil" for millimetre (as in "5 mils of rain fell since 9am") may, however, be confusing.
The abbreviation cc (for cubic centimetre) is also used colloquially for a millilitre, especially in the medical field.
[edit] See also
[edit] References
- ^ Appendix C: General tables of units of measurement. NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. National Institute of Standards and Technology (11 November 2000). Retrieved on 9 October 2006.
- ^ Bureau International des Poids et Mesures (2006). The International System of Units (SI), 159.
