Image: Arago kilogram

Description: The Arago Kilogram, one of the first metric standards used by the United States. It was procured by the US from France in 1821 to serve as primary standard for metric weights. It was made of platinum by the French firm Fortin and certified by French physicist Francoise Arago to be within 1 mg of the "Kilogram of the Archives", the French prototype standard defining the kilogram. In 1866 the US Congress legalized, but did not require the use of metric measures in the United States. It served as the primary US standard for the kilogram until 1889, when the US received the current standards, K4 and K20, from the BIPM. The Arago Kilogram is now part of the NIST museum collection, US National Institute for Standards and Technology, Bethesda, Maryland.
Title: Arago kilogram
Credit: Downloaded 2013-01-17 from Arago Kilogram, Room 3, Weights and Measures, NIST Virtual Museum website, US National Institute for Standards and Technology. No copyright attribution accompanied this image. Disclaimer on NIST site: "With the exception of material marked as copyrighted, information presented on these pages is considered public information and may be distributed or copied."
Author: Unknown
Usage Terms: Public domain
License: Public domain
Attribution Required?: No