WikiPortallus: Pound (mass).html

The word pound comes from the Latin word pendere, meaning "to weigh". The abbreviation lb comes from the Latin word libra, meaning "scales, balances", which also described a Roman unit similar to the pound.

Definitions

Historically, in different parts of the world, at different points in time, and for different applications, the pound (or its translation) has referred to broadly similar but not identical standards of mass or weight.

British pounds

There is a historical link between the pound as a unit of mass and the pound as a unit of currency. Originally the pound sterling was equivalent to the value of a Tower pound of silver (worth about £56 or about $92 US² today). In 1528, the standard was changed to the Troy pound (worth about £60 or $99 today).

Avoirdupois pound

The avoirdupois pound was invented by London merchants in 1303. Originally it was based on independent standards. During the reign of Henry VIII of England, the avoirdupois pound was redefined as 7,000 troy grains.^{citation needed} Since then, the grain has often been considered as a part of the avoirdupois system. By 1758, two standard weights for the avoirdupois pound existed, and when measured in troy grains they were found to be of 7,002 grains and 6,999 grains.³

In the United Kingdom, the avoirdupois pound was defined as a unit of mass by the Weights and Measures Act of 1878, but having a different value (in relation to the kilogram) than it does now, of approximately 0.453592338 kg, which would make the kilogram approximately equal to 2.20462278 pounds. (This was a measured quantity, with the independently maintained artifact still serving as the official standard for this pound.) This old value is sometimes called the imperial pound, and this definition and terminology are obsolete unless referring to the slightly-different 1878 definition. In 1883 it was determined that 0.453592427 kg was a better approximation. With the Weights and measures Act 1889 the United Kingdom legally defined the avoirdupois pound as the rounded value of 0.45359243 kg.⁴

In the United States, the (avoirdupois) pound as a unit of mass has been officially defined in terms of the kilogram since the Mendenhall Order of 1893. In 1893, the relationship was specified to be 2.20462 pounds per kilogram. In 1894, the relationship was specified to be 2.20462234 pounds per kilogram. This change followed a determination of the British pound.⁴

According to a 1959 NIST publication, the international pound differed from the United States 1894 pound by approximately one part in 10 million.⁵. The difference is so insignificant that it can be ignored for almost all practical purposes.⁶

International pound

In 1958 the United States and countries of the Commonwealth of Nations agreed upon common definitions for the pound and the yard. The international avoirdupois pound was defined as exactly 453.59237 grams.

In the United Kingdom, the use of the international pound was implemented in the Weights and Measures Act 1963.⁷

An avoirdupois pound is equal to 16 avoirdupois ounces and to exactly 7,000 grains. The conversion factor between the kilogram and the international pound was therefore chosen to be divisible by 7, and an (international) grain is thus equal to exactly 64.79891 milligrams.

Troy pound

The troy pound takes its name from the French market town of Troyes in France where English merchants traded at least as early as the time of Charlemagne (early ninth century). The system of Troy weights was used in England by apothecaries and jewellers.

A troy pound is equal to 12 troy ounces and to 5,760 grains. Today, the grain is common to the avoirdupois and troy systems of units of mass making an international troy pound equal to 373.241 721 grams.

The troy pound is no longer in general use. In Canada, Australia, the United Kingdom, and other places the troy pound is no longer a legal unit for trade.^{citation needed} In the United Kingdom, the use of the troy pound was abolished on 6 January 1879. The troy ounce is still used for measurements of precious metals such as gold, silver, and platinum, and sometimes gems such as opals.

Most measurements of the mass of precious metals using pounds refer to troy pounds, even though it is not always explicitly stated that this is the case. Some notable exceptions are:

Tower pound

The tower pound was based on the wheat grain unlike all the other English measures, where the grain was based on the barley grain.

Merchants' pound

The merchants' pound (mercantile pound, libra mercantoria or commercial pound) was equal to 9,600 wheat grains (15 tower ounces or 6,750 grains). It was used in England until the 14th century for most goods (other than money, spices and electuaries).⁸

London pound

A London pound was equal to 7,200 troy grains (16 tower ounces or, equivalently, 15 troy ounces).

Wool pound

The wool pound was equal to 6,992 grains. It was a unit of mass used to measure the quantity of wool.⁹

Roman libra

The libra (Latin for "scales / balance") is an ancient Roman unit of mass that was equivalent to approximately 327 grams. It was divided into 12 uncia, or ounces. The libra is the origin of the abbreviation for pound, lb.

French livre

Since the Middle Ages various pounds have been used in France. The word pound translates to livre in French, a word which continues to be used today to refer to a metric pound.

The livre esterlin was equivalent to about 367.1 grams (5,665 gr) and was used between the late ninth and the mid-fourteenth centuries.¹⁰

The livre poids de marc or livre de Paris was equivalent to about 489.5 grams (7,555 gr) and was used between the 1350s and the late 18th century.¹⁰. It was introduced by the government of John II.

The livre métrique was set equal to the kilogram by the decree of 13 Brumaire an IX between 1800 and 1812. This was a form of official metric pound.¹⁰

Russian funt

Jersey pound

A Jersey pound is an obsolete unit of mass used on the island of Jersey from the 14th century to the 19th century. It was equivalent to about 7,561 grains. It may have been derived from the French livre poids de marc.¹¹

Trone pound

Metric pounds

In many countries upon the introduction of a metric system, the pound (or its translation) became an informal term for half of a kilogram or 500 grams, often following an official redefinition of an existing unit during the 19th century. The Dutch pond is an exception. It was officially redefined as 1 kilogram, with an ounce of 100 grams, but people seldom use it this way. In daily life pond is exclusively used for amounts of 500 grams, and to a lesser extent, ons for 100 grams.

Hundreds of older pounds were replaced in this way. Examples of the older pounds are one of around 459 to 460 grams in Spain, Portugal, and Latin America; one of 498.1 grams in Norway; and several different ones in what is now Germany.

Although the use of the pound as an informal term persists in these countries to a varying degree, scales and measuring devices are denominated only in grams and kilograms. A pound of product must be determined by weighing the product in grams. The use of the term pound is usually forbidden for official use in trade.

Use in commerce

See also 21CFR201 Part 201.51 – "Declaration of net quantity of contents" for general labeling and prescription labeling requirements.

From paragraph "a" above, although the avoirdupois pound is a measure of mass, in commerce it is used with the term "Net Weight", because "there is a firmly established general consumer usage and trade custom of declaring the contents of a liquid by weight, or a solid..."

References

^ Grains and drams, ounces and pounds, stones and tons.
^ In the above calculations, these numbers were used: Silver is about $10 per troy oz today, and there are 11.25 troy oz in 5,400 grains. There are approximately 1.65 USD($) to the GBP (£).
^ Skinner, F.G. (1952). "The English Yard and Pound Weight". Bulletin of the British Society for the History of Science.
^ ^a ^b Barbrow, L.E.; Judson, L.V. (1976). Weights and measures standards of the United States – A brief history.
^ United States National Bureau of Standards (1959-06-25). "Notices "Refinement of values for the yard and the pound"". Retrieved on 2006-08-12.
^ United States National Bureau of Standards. ""Appendix C of NIST Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, General Tables of Units of Measurement")". "In Great Britain, the yard, the avoirdupois pound, the troy pound, and the apothecaries pound are identical with the units of the same names used in the United States." (The introduction to this appendix makes it clear that the appendix is only for convenience and has no normative value: "In most of the other tables, only a limited number of decimal places are given, therefore making the tables better adopted to the average user.")
^ Quoted by Laws LJ in "[2002] EWHC 195 (Admin)". Retrieved on 2006-08-12.
^ Zupko, Ronald (1985-12-01). Dictionary of Weights and Measures for the British Isles: The Middle Ages to the 20th Century. DIANE Publishing. ISDN 087169168X.
^ "English Weights & Measures". Retrieved on 2006-08-12.
^ ^a ^b ^c ^d Sizes, Inc. (2001-03-16). "Pre-metric French units of mass livre and smaller". Retrieved on 2006-08-12.
^ Sizes, Inc. (2003-07-28). "Jersey pound". Retrieved on 2006-08-12.

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