Council Directive of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC (80/181/EEC)

[X1 4. UNITS AND NAMES OF UNITS PERMITTED IN SPECIALIZED FIELDS ONLY U.K.

Quantity	Unit
	Name	Symbol	Value
Vergency of optical systems	dioptre*		1 dioptre = 1 m -1
Mass of precious stones	metric carat		1 metric carat = 2 × 10 -4 kg
Area of farmland and building land	are	a	1 a = 10 2 m 2
Mass per unit length of textile yarns and threads	tex*	tex*	1 tex = 10 -6 kg · m -1
[F1 Blood pressure and pressure of other body fluids	Millimetre of mercury	mm Hg(*)	1 mm Hg = 133,322 Pa
Effective cross-sectional area	Barn	b	1 b = 10 -28 m 2]

Note: U.K.

[F2 The prefixes and their symbols listed in 1.3 may be used in conjunction with the above units and symbols, with the exception of the millimetre of mercury and its symbol. The multiple of 10 ² a is, however, called a ‘ hectare ’ .] ] U.K.

Editorial Information

X1 Substituted by Corrigendum to Council Directive 80/181/EEC of 20 December 1979 on the aproximation of the laws of the Member States relating to units of measurement and on the repeal of Directive 71/354/EEC (Official Journal of the European Communities No L 39 of 15 February 1980).