The Scots gallon (Scottish Gaelic: galan)[1] was a unit of liquid volume measurement that was in use in Scotland from at least 1661 – and possibly as early as the 15th century – until the late 19th century. It was approximately equivalent to 13.568 litres, or very roughly three times larger than the Imperial gallon that was adopted in 1824. A Scots gallon could be subdivided into eight Jougs (or Scots pints, of 1696 mL each), or into sixteen chopins (of 848 mL each).[2]
An ale or beer barrel was 12 Scots gallons (35.81 Imperial gallons [162.816 litres]).[3]
^Kay, Christian; Mackay, Margaret A. Perspectives on the Older Scottish Tongue: A Celebration of DOST. Edinburgh University Press. p. 150.
^Articles of Union (1707), Article VII (tax on liquor). That all parts of the United Kingdom be for ever from and after the Union lyable to the same Excises upon all Exciseable Liquors excepting only that the 34 Gallons English Barrel of Beer or Ale amounting to 12 Gallons Scots present measure sold in Scotland by the Brewer at 9/6d Sterling excluding all Duties and Retailed including Duties and the Retailer's profit at 2d the Scots pint or eight part of the Scots Gallon, be not after the Union lyable on account of the present Excise upon Exciseable Liquors in England, to any higher Imposition than 2s[hillings] Sterling upon the forsaid 34 Gallons English barrel, being 12 gallons the present Scots measure And that the Excise settled in England on all other Liquors when the Union commences take place throughout the whole United Kingdom.