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The Carat system is increasingly being complemented or superseded by the millesimal fineness system, in which the purity of precious metals is denoted by parts per thousand of pure metal in the alloy.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:
“Like all writers, he measured the achievements of others by what they had accomplished, asking of them that they measure him by what he envisaged or planned.”
—Jorge Luis Borges (1899–1986)
“Since we are assured that the all-wise Creator has observed the most exact proportions of number, weight and measure in the make of all things, the most likely way therefore to get any insight into the nature of those parts of the Creation which come within our observation must in all reason be to number, weigh and measure.”
—Stephen Hales (1677–1761)
“Marching is when the pulse of the hero beats in unison with the pulse of Nature, and he steps to the measure of the universe; then there is true courage and invincible strength.”
—Henry David Thoreau (1817–1862)