Note 36 — Chapter XIII · MEASURES OF VALUE

‘Twenty-four carat’ was taken as the standard of pure gold because the Roman gold solidus weighed twenty-four carats (each 1/144 of an ounce). The assayer’s carat is 1/24 part divided into four assay-grains. Medieval gold coins such as Edward III’s noble and the Venetian zechin, always of the same quaint pattern, were generally twenty-three carat 3-1/2 grains fine, = 995 parts in 1000. But this nearly pure gold being very soft, it became customary to alloy the metal with a certain amount of copper to give it the hardness necessary for trade purposes in modern times.