System of units of mass
Troy weight
is a system of
units
of
mass
that originated in 15th-century
Kingdom of England
[1]
and is primarily used in the
precious metals
industry. The troy weight units are the
grain
, the
pennyweight
(24 grains), the troy ounce (20 pennyweights), and the troy pound (12 troy ounces). The troy grain is equal to the grain unit of the
avoirdupois
system, but the troy ounce is heavier than the avoirdupois ounce, and the troy pound is lighter than the avoirdupois pound. One troy ounce (oz t) equals exactly 31.1034768 grams.
Etymology
[
edit
]
Troy weight is generally supposed to take its name from the French market town of
Troyes
where English merchants traded at least as early as the early 9th century.
[2]
[3]
The name
troy
is first attested in 1390, describing the weight of a platter, in an account of the travels in Europe of the
Earl of Derby
.
[2]
[4]
Charles Moore Watson
(1844?1916) proposes an alternative etymology:
The Assize of Weights and Measures
(also known as
Tractatus de Ponderibus et Mensuris
), one of the
statutes of uncertain date
from the reign of either
Henry III
or
Edward I
, thus before 1307, specifies "
troni ponderacionem
"?which the Public Record Commissioners translate as "troy weight". The word
troni
refers to markets.
[
citation needed
]
Wright's
The English Dialect Dictionary
lists the word
troi
as meaning a
balance
, 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 of
steelyard
called the
auncel
.
[5]
Troy weight referred to the
Tower system
; the earliest reference to the modern troy weights is in 1414.
[5]
[6]
History
[
edit
]
The origin of the troy weight system is unknown. Although the name probably comes from the
Champagne fairs
at
Troyes
, in northeastern France.
[7]
English troy weights were nearly identical to the troy weight system of
Bremen
. (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 the
Roman monetary system
. Before they used coins, early
Romans
used bronze bars of varying weights as currency. An
aes grave
("heavy bronze") weighed one
pound
. One twelfth of an
aes grave
was called an
uncia
, 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 as
Imperial units
) was established in 1824, prior to which the troy weight system was a subset of pre-Imperial
English 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 for
United States
coinage by act of
Congress
on 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 the
Act of Union
which created the
Kingdom 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 the
apothecaries' system
. This was long used in medicine, but has been largely replaced by the
metric 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 with
437
+
1
⁄
2
grains 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 use
International System of Units
(SI),
[12]
[13]
except in
East Asia
.
[14]
However, the
People's Bank of China
has previously used troy measurements in minting
Gold Pandas
beginning 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 is
5
760
grains (
373.241
72
grams). (An avoirdupois pound is approximately 21.53% heavier at
7
000
grains (
453.592
37
grams), and consists of sixteen avoirdupois ounces).
Troy ounce (oz t)
[
edit
]
A troy ounce weighs 480
grains
.
[15]
Since the implementation of the
international yard and pound
agreement of 1 July 1959, the grain measure is defined as precisely
64.798
91
milligrams
.
[16]
: C-19
[17]
Thus one troy ounce = 480 grains ×
0.064
798
91
grams/grain =
31.103
476
80
grams. Since the ounce avoirdupois is defined as 437.5 grains, a troy ounce is exactly
480
⁄
437.5
=
192
⁄
175
or 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)
[
edit
]
The
pennyweight
symbol is
dwt
. 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 the
original pound-sterling
. However, prior to 1526, the English
pound sterling
was based on the
tower pound
, which is
15
⁄
16
of a troy pound. The
d
in
dwt
stands for
denarius
, the ancient Roman coin that equates loosely to a penny. The symbol
d
for penny can be recognized in the form of British pre-decimal pennies, in which pounds, shillings, and pence were indicated using the symbols
£
,
s
, and
d
, respectively.
Troy grain
[
edit
]
There is no specific 'troy grain'. All
Imperial systems
use the same measure of mass called a grain (historically of
barley
), each weighing
1
⁄
7000
of an avoirdupois pound (and thus a little under 65 milligrams).
[a]
Mint masses
[
edit
]
Mint masses, also known as
moneyers' masses
were legalized by Act of Parliament dated 17 July 1649 entitled
An 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
0
|
Troy ounce (20 pennyweights)
|
480
|
31.10347 68
0
|
Pennyweight
|
24
|
1.55517 384
|
Grain
|
1
|
0.06479 891
|
English pounds
Unit
|
Pounds
|
Ounces
|
Grains
|
Metric
|
Avdp.
|
Troy
|
Tower
|
Merchant
|
London
|
Metric
|
Avdp.
|
Troy
|
Tower
|
Troy
|
Tower
|
g
|
kg
|
Avoirdupois
|
1
|
175
/
144
|
= 1.2152
7
|
35
/
27
|
= 1.
296
|
28
/
27
|
= 1.
037
|
35
/
36
|
= 0.97
2
|
? 0.9072
|
16
|
14
+
7
/
12
|
= 14.58
3
|
15
+
5
/
9
|
= 15.
5
|
7,000
|
0
9,955
+
5
/
9
|
? 454
|
?
5
/
11
|
Troy
|
144
/
175
|
? 0.8229
|
1
|
16
/
15
|
= 1.0
6
|
64
/
75
|
= 0.85
3
|
4
/
5
|
= 0.8
|
? 0.7465
|
13
+
29
/
175
|
? 13.17
|
12
|
12
+
4
/
5
|
= 12.8
|
5,760
|
0
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
|
0
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
|
0
9,600
|
? 437
|
?
7
/
16
|
London
|
36
/
35
|
? 1.029
|
5
/
4
|
= 1.25
|
4
/
3
|
= 1.
3
|
16
/
15
|
= 1.0
6
|
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 the
apothecaries' system
but with different further subdivisions.
See also
[
edit
]
- ^
Because an avoirdupois pound weighs 7000 grains and a pound is
legally defined
as having a mass of exactly 0.45359237
kg (453.59237 g, 453592.37 mg), one grain weighs 453592.37/7000
mg (or nominally 64.79891
mg to seven
significant figures
, but this would be an example of
false precision
.)
References
[
edit
]
- ^
a
b
Hallock, 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
. Retrieved
14 August
2012
.
- ^
a
b
"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.
OCLC
250202885
.
…the great fairs established for all Europe the weight-standard
Troyes
, 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
.
- ^
a
b
Watson, Charles Moore (1910).
British weights and measures as described in the laws of England from Anglo-Saxon times
. London: John Murray. p. 82.
OCLC
4566577
.
- ^
Wright, Joseph
(1898).
The English Dialect Dictionary
. Vol. 6. Oxford: English Dialect Society. p. 250.
OCLC
63381077
.
- ^
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.
- ^
a
b
Zupko, Ronald Edward
(1977).
British Weights and Measures: A History from Antiquity to the Seventeenth Century
. University of Wisconsin Press. pp. 28?9.
ISBN
978-0-299-07340-4
.
- ^
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.com
. Princeton University.
Archived
from the original on 2008-02-26
. Retrieved
2008-01-10
.
- ^
"Borse Frankfurt: Aktien, Kurse, Charts und Nachrichten"
.
www.boerse-frankfurt.de
.
Archived
from the original on 1 November 2015
. Retrieved
28 April
2018
.
- ^
"Units of Measure - The Perth Mint"
.
Archived
from the original on 2015-09-24.
- ^
"Do grams or ounces win?"
.
Archived
from the original on 2016-05-06.
- ^
a
b
c
"Units of measure"
.
Perth Mint
. Archived from
the original
on 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"
Archived
2016-06-17 at the
Wayback Machine
(PDF).
Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices
Archived
2016-08-23 at the
Wayback Machine
. NIST Handbook.
44
(2012 ed.). Washington, D.C.: U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology.
ISSN
0271-4027
Archived
2022-12-25 at the
Wayback Machine
.
OCLC
OCLC
58927093
. 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.
OCLC
610190761
. Archived from
the original
(PDF)
on 3 June 2011
. Retrieved
30 June
2012
.
- ^
"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.
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