Definition:Imperial/Volume/Gallon
Definition
The (imperial) gallon is an imperial unit of volume.
\(\displaystyle \) | \(\) | \(\displaystyle 1\) | gallon | ||||||||||
\(\displaystyle \) | \(=\) | \(\displaystyle 2\) | pottles | ||||||||||
\(\displaystyle \) | \(=\) | \(\displaystyle 4 \cdotp 54609\) | litres | ||||||||||
\(\displaystyle \) | \(=\) | \(\displaystyle 4 \, 546 \cdotp 09\) | millilitres |
Also known as
The imperial gallon is also known as the UK gallon in order specifically to distinguish it from the US gallon.
Also see
Historical Note
Prior to $1824$, there existed a number of different gallons throughout the British Empire.
The imperial gallon was defined in $1824$ as a volume close to the ale gallon.
Its original definition was the volume of $10$ pounds (approximately $4.5$ kilograms) of distilled water, weighed in air with brass weights with the barometer standing at $30$ inches of mercury ($102$ kilopascals) at a temperature of $62$ degrees Fahrenheit ($17$ degrees Celsius).
In $1963$, the imperial gallon was redefined as the volume of $10$ pounds of distilled water of density $0 \cdotp 998859$ grams per millilitre weighed in air of density $0 \cdotp 001217$ grams per millilitre against weights of density $8 \cdotp 136$ grams per millilitre.
This works out to be $4.546096$ litres or $277.4198$ cubic inches.
The imperial gallon was redefined once again in $1985$ to be exactly $4 \cdotp 54609$ litres by the Weights and Measures Act.
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $2$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $2$
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): Entry: gallon Symbol: gal.${}$: 1.