The dry gallon, also known as the corn gallon or grain gallon, is a historic British dry measure of volume that was used to measure grain and other dry commodities and whose earliest recorded official definition, in 1303, was the volume of 8 pounds (3.6 kg) of wheat.[1] It is not used in the US customary system – though it implicitly exists since the US dry measures of bushel, peck, quart, and pint are still used – and is not included in the National Institute of Standards and Technology handbook that many US states recognize as the authority on measurement law.[2][3]
The US fluid gallon is about 14.1% smaller than the US dry gallon, while the Imperial fluid gallon is about 3.2% larger than the US dry gallon.
The dry gallon's implicit value in the US system was originally one eighth of the Winchester bushel, which was a cylindrical measure of 18.5 inches (469.9 mm) in diameter and 8 inches (203.2 mm) in depth, making it an irrational number of cubic inches; its value to seven significant digits was 268.8025 cubic inches (4.404884 litres), from an exact value of 9.252 × π cubic inches. Since the bushel was later redefined to be exactly 2150.42 cubic inches, 268.8025 became the exact value for the dry gallon (268.8025 cubic inches is 4.40488377086 L).[citation needed]
References
edit- ^ ""How Many? A Dictionary of Units of Measurement" by Russ Rowlett and the University of North Carolina at Chapel Hill". Archived from the original on 2012-02-18. Retrieved 2012-01-20.
- ^ 101st Conference on Weights and Measures 2016. (2017). Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. National Institute of Standards and Technology. p. C-6, C-11, C-16.
- ^ Summary of State Laws and Regulations in Weights and Measures Archived December 5, 2011, at the Wayback Machine. (2005) National Institute of Standards and Technology.
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