was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of fineness (that is, 99.2% purity) could have been described as being 23-karat, 3-grain, 1-quart gold. The karat fractional system is increasingly being complemented or superseded by the millesimal system, described above. Conversion between percentage of pure gold and karats: 58.33–62.50% = 14K (acclaimed 58.33%) 75.00–79.16% = 18K (acclaimed 75.00%) 91.66–95.83% = 22K (acclaimed 91.66%) 95.83–99.95% = 23K (acclaimed 95.83%) 99.95–100% = 24K (acclaimed 99.95%) Volume However, this system of calculation gives only the mass of pure gold contained in an alloy. The term 18-karat gold means that the alloy's mass consists of 75% of gold and 25% of other metal(s). The quantity of gold by volume in a less-than-24-karat gold alloy differs according to the alloy(s) used. For example, knowing that standard 18-karat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm3 for gold, 10.49 g/cm3 for silver and 8.96 g/cm3 for copper. This formula gives the amount of gold in cubic centimeters or in milliliters in an alloy: where VAu is the volume of gold in cubic centimeters or in milliliters, Ma is the total mass of the alloy in grams, and kt is the karat purity of the alloy. To have the percentage of the volume of gold in an alloy, divide the volume of gold in cubic centimetres or in millilitres by the total volume of the alloy in cubic centimetres or in millilitres. For 10-carat gold, the gold volume in the alloy represents about 26% of the total volume for standard yellow gold. Talking about purity according to mass could lead to some misunderstandings; for many people, purity means volume. Etymology Karat is a variant of carat. First attested in English in the mid-15th century, the word carat came from Middle French , in turn derived either from Italian or Medieval Latin . These were borrowed into Medieval Europe from the Arabic meaning "fruit of the carob tree", also "weight of 5 grains", () and was a unit of mass though it was probably not used to measure gold in classical times. The Arabic term ultimately originates from the Greek () meaning carob seed (literally "small