Troy weightis a system ofunitsofmassthat originated in theKingdom of Englandin the 15th century[1]and is primarily used in theprecious metalsindustry. The troy weight units are thegrain,thepennyweight(24 grains), the troy ounce (20 pennyweights), and the troy pound (12 troy ounces). The troy grain is equal to the grain unit of theavoirdupoissystem, but the troy ounce is heavier than the avoirdupois ounce, and the troy pound is lighter than the avoirdupois pound. Legally, one troy ounce (oz t) equals exactly 31.1034768 grams.
Etymology
editTroy weight is generally supposed to take its name from the French market town ofTroyeswhere English merchants traded at least as early as the early 9th century.[2][3]The nametroyis first attested in 1390, describing the weight of a platter, in an account of the travels in Europe of theEarl of Derby.[2][4]
Charles Moore Watson(1844–1916) proposes an alternative etymology:The Assize of Weights and Measures(also known asTractatus de Ponderibus et Mensuris), one of thestatutes of uncertain datefrom the reign of eitherHenry IIIorEdward I,thus before 1307, specifies "troni ponderacionem"—which the Public Record Commissioners translate as" troy weight ". The wordtronirefers to markets.[citation needed]Wright'sThe English Dialect Dictionarylists the wordtroias meaning abalance,related to the alternate form 'tron' which also means market or the place of weighing. From this, Watson suggests that 'troy' derives from the manner of weighing by balance precious goods such as bullion or drugs; in contrast to the word 'avoirdupois' used to describe bulk goods such as corn or coal, sometimes weighed in ancient times by a kind ofsteelyardcalled theauncel.[5]
Troy weight referred to theTower system;the earliest reference to the modern troy weights is in 1414.[5][6]
History
editThe origin of the troy weight system is unknown. Although the name probably comes from theChampagne fairsatTroyes,in northeastern France.[7]English troy weights were nearly identical to the troy weight system ofBremen.(The Bremen troy ounce had a mass of 480.8 British Imperial grains.)[8]
Many aspects of the troy weight system were indirectly derived from theRoman monetary system.Before they used coins, earlyRomansused bronze bars of varying weights as currency. Anaes grave( "heavy bronze" ) weighed onepound.One twelfth of anaes gravewas called anuncia,or in English, an "ounce". Before the adoption of the metric system, many systems of troy weights were in use in various parts of Europe, among them Holland troy, Paris troy, etc.[9]Their values varied from one another by up to several percentage points. Troy weights were first used in England in the 15th century and were made official for gold and silver in 1527.[1]The British Imperial system of weights and measures (also known asImperial units) was established in 1824, prior to which the troy weight system was a subset of pre-ImperialEnglish units.
The troy ounce in modern use is essentially the same as the British Imperial troy ounce (1824–1971), adopted as an official weight standard forUnited Statescoinage by act ofCongresson May 19, 1828.[10]The British Imperial troy ounce (known more commonly simply as the imperial troy ounce) was based on, and virtually identical with, the pre-1824 British troy ounce and the pre-1707 English troy ounce. (1824 was the year the British Imperial system of weights and measures was adopted; 1707 was the year of theAct of Unionwhich created theKingdom of Great Britain.) Troy ounces have been used in England since the early 15th century, and the English troy ounce was officially adopted for coinage in 1527. Before that time, various sorts of troy ounces were in use on the continent.[8]
The troy ounce and grain were also part of theapothecaries' system.This was long used in medicine, but has been largely replaced by themetric system(milligrams).[11]The only troy weight in widespread use is the British Imperial troy ounce and its American counterpart. Both are based on a grain of 0.06479891 gram (exact, by definition), with 480 grains to a troy ounce (compared with437+1⁄2grains for an ounce avoirdupois). The British Empire abolished the 12-ounce troy pound in the 19th century. It has been retained, though rarely used, in the American system. Larger amounts of precious metals are conventionally counted in hundreds or thousands of troy ounces, or in kilograms.
Troy ounces have been and are still often used in precious metal markets in countries that otherwise useInternational System of Units(SI),[12][13]except inEast Asia.[14]However, thePeople's Bank of Chinahas previously used troy measurements in mintingGold Pandasbeginning in 1982; since 2016, the use of troy ounces has been replaced by integer numbers of grams.
Units of measurement
edit
Troy pound (lb t)
edit
The troy pound (lb t) consists of twelve troy ounces[15]and thus is5760grains (373.24172grams). (An avoirdupois pound is approximately 21.53% heavier at7000grains (453.59237grams), and consists of sixteen avoirdupois ounces).
Troy ounce (oz t)
editA troy ounce weighs 480grains.[15]Since the implementation of theinternational yard and poundagreement of 1 July 1959, the grain measure is defined as precisely64.79891milligrams.[16]: C-19 [17]Thus one troy ounce = 480 grains ×0.06479891grams/grain =31.10347680grams. Since the ounce avoirdupois is defined as 437.5 grains, a troy ounce is exactly480⁄437.5=192⁄175or about 1.09714 ounces avoirdupois or about 9.7% more. The troy ounce for trading precious metals is considered to be sufficiently approximated by 31.10 g in EU directive 80/181/EEC.[18]
The Dutch troy system is based on a mark of 8 ounces, the ounce of 20 engels (pennyweights), the engel of 32 as. The mark was rated as 3,798 troy grains or 246.084 grammes. The divisions are identical to the tower system.[19]
Pennyweight (dwt)
editThepennyweightsymbol isdwt.One pennyweight weighs 24 grains, and 20 pennyweights make one troy ounce.[15]Because there were 12 troy ounces in the old troy pound, there would have been 240 pennyweights to the pound (mass) – just as there were 240 pennies in theoriginal pound-sterling.However, prior to 1526, the Englishpound sterlingwas based on thetower pound,which is15⁄16of a troy pound. Thedindwtstands fordenarius,the ancient Roman coin that equates loosely to a penny. The symboldfor penny can be recognized in the form of British pre-decimal pennies, in which pounds, shillings, and pence were indicated using the symbols£,s,andd,respectively.
Troy grain
editThere is no specific 'troy grain'. AllImperial systemsuse the same measure of mass called a grain (historically ofbarley), each weighing1⁄7000of an avoirdupois pound (and thus a little under 65 milligrams).[a]
Mint masses
editMint masses, also known asmoneyers' masses,were legalized by Act of Parliament dated 17 July 1649 entitledAn Act touching the monies and coins of England.A grain is 20 mites, a mite is 24 droits, a droit is 20 perits, a perit is 24 blanks.[20][21]
Conversions
edit| Unit | Grains | Grams (exact) |
|---|---|---|
| Troy pound (12 troy ounces) | 5,760 | 373.24172 16 |
| Troy ounce (20 pennyweights) | 480 | 31.10347 68 |
| Pennyweight | 24 | 1.55517 384 |
| Grain | 1 | 0.06479 891 |
| Unit | Pounds | Ounces | Grains | Metric | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avdp. | Troy | Tower | Merchant | London | Metric | Avdp. | Troy | Tower | Troy | Tower | g | kg | |||||||||
| Avoirdupois | 1 | 175/144 | = 1.21527 | 35/27 | = 1.296 | 28/27 | = 1.037 | 35/36 | = 0.972 | ≈ 0.9072 | 16 | 14+7/12 | = 14.583 | 15+5/9 | = 15.5 | 7,000 | 9,955+5/9 | ≈ 454 | ≈5/11 | ||
| Troy | 144/175 | ≈ 0.8229 | 1 | 16/15 | = 1.06 | 64/75 | = 0.853 | 4/5 | = 0.8 | ≈ 0.7465 | 13+29/175 | ≈ 13.17 | 12 | 12+4/5 | = 12.8 | 5,760 | 8,192 | ≈ 373 | ≈3/8 | ||
| Tower | 27/35 | ≈ 0.7714 | 15/16 | = 0.9375 | 1 | 4/5 | = 0.8 | 3/4 | = 0.75 | ≈ 0.6998 | 12+12/35 | ≈ 12.34 | 11+1/4 | = 11.25 | 12 | 5,400 | 7,680 | ≈ 350 | ≈7/20 | ||
| Merchant | 27/28 | ≈ 0.9643 | 75/64 | = 1.171875 | 5/4 | = 1.25 | 1 | 15/16 | = 0.9375 | ≈ 0.8748 | 15+3/7 | ≈ 15.43 | 14+1/16 | = 14.0625 | 15 | 6,750 | 9,600 | ≈ 437 | ≈7/16 | ||
| London | 36/35 | ≈ 1.029 | 5/4 | = 1.25 | 4/3 | = 1.3 | 16/15 | = 1.06 | 1 | ≈ 0.9331 | 16+16/35 | ≈ 16.46 | 15 | 16 | 7,200 | 10,240 | ≈ 467 | ≈7/15 | |||
| Metric | ≈ 1.1023 | ≈ 1.3396 | ≈ 1.4289 | ≈ 1.1431 | ≈ 1.0717 | 1 | ≈ 17.64 | ≈ 16.08 | ≈ 17.15 | 7,716 | 10,974 | = 500 | =1/2 | ||||||||
The troy system was used in theapothecaries' systembut with different further subdivisions.
See also
edit- Bullion coin
- Carat (mass)
- Conversion of units
- Fluid ounce
- Mark (unit)
- Tola (unit),a traditional unit of mass equal to exactly3⁄8of a troy ounce
- United States customary units
Explanatory footnotes
edit- ^Because an avoirdupois pound weighs 7000 grains and a pound islegally definedas having a mass of exactly 0.45359237kg (453.59237 g, 453592.37 mg), one grain weighs 453592.37/7000mg (or nominally 64.79891mg to sevensignificant figures,but this would be an example offalse precision.)
References
edit- ^abHallock, William;Wade, Herbert Treadwell (1906).Outlines of the Evolution of Weights and Measures and the Metric System.New York and London: The Macmillan Company. p.34.Retrieved14 August2012.
- ^ab"troy, n.2".Oxford English Dictionary.Oxford, England: Oxford University Press. June 2012.
The received opinion is that it took its name from a weight used at the fair of Troyes in France
- ^Partridge, Eric(1958)."Trojan".Origins: A Short Etymological Dictionary of Modern English.London: Routledge and Kegan Paul. p. 3566.OCLC250202885.
...the great fairs established for all Europe the weight-standardTroyes,whence...Troy...
- ^Smith, L. Toulmin(1894).Expeditions to Prussia and the Holy Land Made by Henry Earl of Derby (afterwards King Henry IV.) in the Years 1390-1 and 1392-3.London: Camden Society. p.100.
- ^abWatson, Charles Moore (1910).British weights and measures as described in the laws of England from Anglo-Saxon times.London: John Murray. p. 82.OCLC4566577.
- ^Wright, Joseph(1898).The English Dialect Dictionary.Vol. 6. Oxford: English Dialect Society. p. 250.OCLC63381077.
- ^Smith, Adam (1809).An Inquiry Into the Nature and Causes of the Wealth of Nations.Vol. 1. London: T. Hamilton. p. 35.
The French livre contained, in the time of Charlemagne, a pound, Troyes weight, of silver of a known finess. The fair of Troyes in Champaign was at that time frequented by all the nations of Europe, and the weights and measures of so famous a market were generally known and esteemed.
- ^abZupko, Ronald Edward(1977).British Weights and Measures: A History from Antiquity to the Seventeenth Century.University of Wisconsin Press. pp. 28–9.ISBN978-0-299-07340-4.
- ^Kelly, Patrick (1811).The Universal Cambist and Commercial Instructor.Vol. 1. p. 20.
- ^Hallock, Wade (1906).Outlines of the evolution of weights and measures and the metric system.The Macmillan company. p.119.
- ^"Troy Ounce".WordNet 3.0, Dictionary.Princeton University.Archivedfrom the original on 2008-02-26.Retrieved2008-01-10.
- ^"Börse Frankfurt: Aktien, Kurse, Charts und Nachrichten".boerse-frankfurt.de.Archivedfrom the original on 1 November 2015.Retrieved28 April2018.
- ^"Units of Measure - The Perth Mint".Archivedfrom the original on 2015-09-24.
- ^"Do grams or ounces win?".Archivedfrom the original on 2016-05-06.
- ^abc"Units of measure".Perth Mint.Archived fromthe originalon 7 June 2019.
- ^National Institute of Standards and Technology (October 2011). Butcher, Tina; Cook, Steve; Crown, Linda et al. eds."Appendix C – General Tables of Units of Measurement"Archived2016-06-17 at theWayback Machine(PDF).Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring DevicesArchived2016-08-23 at theWayback Machine.NIST Handbook.44(2012 ed.). Washington, D.C.: U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology.ISSN0271-4027Archived2022-12-25 at theWayback Machine.OCLCOCLC58927093.Retrieved 30 June 2012.
- ^Judson, Lewis V. (March 1976) [October 1963]."8. Refinement of values for the yard and pound".Weights and Measures Standards of the United States: A brief history(PDF).NBS Special Publication. Vol. 447. Washington, D.C.: U.S. Department of Commerce, National Bureau of Standards. p. 20.OCLC610190761.Archived fromthe original(PDF)on 3 June 2011.Retrieved30 June2012.
- ^"Consolidated TEXT: 31980L0181 — EN — 13.06.2020".
- ^Kelly, Patric (1835).Universal Cambist.London.
- ^A new English dictionary on historical principles: founded mainly on the materials collected by the Philological Society.Philological Society (Great Britain). 1891. p. 675 – via Clarendon Press.
- ^Miege, Guy (1738).The Present State of Great Britain and Ireland.J. Brotherton, A. Bettesworth and C. Hitch, G. Strahan, W. Mears, R. Ware, E. Symon, and J. Clark. p. 307.