Beginning in the 1570s, it was used to measure weights of diamonds. ===Standardization=== An 'international carat' of 205 milligrams was proposed in 1871 by the Syndical Chamber of Jewellers, etc., in Paris, and accepted in 1877 by the Syndical Chamber of Diamond Merchants in Paris.
Beginning in the 1570s, it was used to measure weights of diamonds. ===Standardization=== An 'international carat' of 205 milligrams was proposed in 1871 by the Syndical Chamber of Jewellers, etc., in Paris, and accepted in 1877 by the Syndical Chamber of Diamond Merchants in Paris.
It was soon made compulsory by law in France, but uptake of the new carat was slower in England, where its use was allowed by the Weights and Measures (Metric System) Act of 1897. ==Historical definitions== === UK Board of Trade === In the United Kingdom the original Board of Trade carat was exactly grains (~3.170 grains = ~205 mg); in 1888, the Board of Trade carat was changed to exactly grains (~3.168 grains = ~205 mg).
It was soon made compulsory by law in France, but uptake of the new carat was slower in England, where its use was allowed by the Weights and Measures (Metric System) Act of 1897. ==Historical definitions== === UK Board of Trade === In the United Kingdom the original Board of Trade carat was exactly grains (~3.170 grains = ~205 mg); in 1888, the Board of Trade carat was changed to exactly grains (~3.168 grains = ~205 mg).
The carat (ct) is a unit of mass equal to or 0.00643 troy oz, and is used for measuring gemstones and pearls. The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterwards in many countries around the world.
A metric carat of 200 milligrams – exactly one-fifth of a gram – had often been suggested in various countries, and was finally proposed by the International Committee of Weights and Measures, and unanimously accepted at the fourth sexennial General Conference of the Metric Convention held in Paris in October 1907.
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