Litre
From Free net encyclopedia
The litre (spelled litre in Commonwealth English and liter in American English) is a unit of volume. There are two official symbols, the Latin letter el in both cases: l and L. The litre is not an SI unit but is accepted for use with the SI. The SI unit of volume is the cubic metre (m³).
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Definitions and equivalents
A litre is defined as a special name for a cubic decimetre (1 L = 1 dm³).
- 1 L = 1000 cm³ (exactly)
- 1000 L = 1 m³ (exactly)
SI prefixes applied to the litre
The litre may be used with some SI prefixes.
| 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 | |
Name origin
The word "litre" is derived from an older French unit, the litron, whose name came from Greek via Latin.
Other common metric equivalencies
- 1 µL (microlitre) = 1 mm³ (cubic millimetre)
- 1 mL (millilitre) = 1 cm³ (cubic centimetre)
Conversions
One litre
- ≈ 0.87987699 Imperial quart
- Inverse: One Imperial quart ≡ 1.1365225 litres
- ≈ 1.056688 US fluid quarts
- Inverse: One US fluid quart ≡ 0.946352946 litres
- ≈ 0.0353146667 cubic foot
- Inverse: One cubic foot ≡ 28.316846592 litres
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. Similarly: 1 mL of water has about 1 g of mass; 1000 litres of water has about 1000 kg (1 tonne) of mass. This relationship is due to the history of the unit, but since 1964 it has not been part of the definition.
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 l key had to be used to type the numeral 1. Further, in some typefaces the two characters are nearly indistinguishable. 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.
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.
History
In 1793, 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 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. NIST Reference
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.
See also
External links
- BIPM's "SI Brochure"
- BIPM's "(Table 6 -) Non-SI units accepted for use with the International System"
- NIST note on SI units
- NIST recommends uppercase letter L
- UK National physical laboratory's "Internationally recognised non SI units" pageast:Llitru
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