karat

1

A unit of proportion indicating what part of an alloy is precious metal. Pure, unalloyed gold is 24 karat; 12-karat gold is ¹²/₂₄, or 50% gold, and so on. In the United States it is spelled with an initial “k,” to distinguish it from the carat, a unit of mass, but in much of the world it is spelled with a “c.”

The word is from the Arabic qirat, which represented the ratio ¹/₂₄ much as in English the word “nail” used to represent ¹/₁₆ of a larger unit, sometimes ¹/₁₆ of a yard and sometimes ¹/₁₆ of a hundredweight. In Lebanon today, for example, one kirat is ¹/₂₄th of a drah. (UN 1966)

Pure gold is quite soft and not suitable for objects like rings; a ring is made of 18-karat gold alloy to improve performance, not to save on the cost of materials. Alloys below 14 karat, however, are liable to crack.

2

In German-speaking Europe, the Karat of Cologne, a unit of mass used for gold and silver, = ⁹/₁₆₀ Quentchen, about 205.5 milligrams. In Frankfurt am Main, however, 1 Karat = ¹/₁₁₅₆ Mark, about 205.8 mg. Article 4 of the law¹ establishing the metric system in Austria specified that the Wiener Karat (Vienna karat) was equivalent to 205.969 gram.

Gesetz of 23 July 1871, R.G.B 1872, No. 16. The law is reproduced in
Georg Thaa.
Das Mass- und Gewichtwesen und der Richdienst in Österreich.
Volume 13 of Taschenausgabe de österreichischen Gesetze.
Vienna: Munz'sche k. u. k. Hof- Verlags- und Universitats-Buchhandlung, 1900.

3

In Norway and Denmark, a unit of fineness of precious metals, = 1/24 mark = 4 gran = 12 gren, about 4.17 %.