Measure
Carat purity is measured as 24 times the purity by mass:
where
- is the carat rating of the material,
- is the mass of pure gold or platinum in the material, and
- is the total mass of the material.
Therefore, 24-Carat gold is fine (99.9% Au w/w), 18-Carat gold is 18 parts gold 6 parts another metal (forming an alloy), 12-Carat gold is 12 parts gold (12 parts another metal), and so forth.
In England, the carat 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-carat, 3-grain, 1-quart gold.
The Carat system is increasingly being complemented or superseded by the millesimal fineness system, in which the purity of precious metals is denoted by parts per thousand of pure metal in the alloy.
Read more about this topic: Carat (purity)
Famous quotes containing the word measure:
“The soul is no longer honored as it once was, but it still keeps appetite from being the measure of all things.”
—Mason Cooley (b. 1927)
“The measure of your quality as a public person, as a citizen, is the gap between what you do and what you say.”
—Ramsey Clark (b. 1927)
“The gifts he gave were that some would be apostles, some prophets, some evangelists, some pastors and teachers, to equip the saints for the work of ministry, for building up the body of Christ, until all of us come to the unity of the faith and of the knowledge of the Son of God, to maturity, to the measure of the full stature of Christ.”
—Bible: New Testament, Ephesians 4:11.