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File:Standard kilogram, 2.jpg

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Summary

Description
English: A national prototype kilogram standard mass, number K4, kept by the National Institute of Standards and Technology, USA, one of two which serve as the official standard for defining all units of weight and mass in the United States. It is a polished cylinder made of 90% platinum - 10% iridium alloy, 39 mm (1.5 inches) in diameter and 39 mm high. It is an exact copy of the international prototype kilogram kept at the International Bureau of Weights and Measures (Bureau International des Poids et Measures) in Sevres, France It was one of 40 copies which were presented by France in 1884 to different nations as national standards. This copy, K4, serves as a secondary comparison standard, while its twin, K20, serves as the primary standard. In 1884, it differed in mass from the prototype kilogram by about 75 micrograms. Alterations to image: Removed aliasing artifacts (stripes) due to scanning of halftone photo using GIMP FFT filter.
Date
Source National Geographic magazine, Vol. 27, No.1 (January 1915), p. 154, on Google Books. Photo credited to US National Bureau of Standards, now National Institute of Standards and Technology (NIST).
Author Unknown authorUnknown author
Permission
(Reusing this file)		 Original work of the US federal government.

Licensing

Public domain
This image is in the public domain in the United States because it is a work of the United States Federal Government, specifically an employee of the National Institute of Standards and Technology, under the terms of Title 17, Chapter 1, Section 105 of the US Code.

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Captions

this file represents the kilogram standard

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Date/TimeThumbnailDimensionsUserComment
current09:45, 14 January 2013Thumbnail for version as of 09:45, 14 January 2013708 × 808 (119 KB)ChetvornoHigher resolution image
22:45, 17 February 2011Thumbnail for version as of 22:45, 17 February 2011438 × 499 (52 KB)Quibik== {{int:filedesc}} == {{Information |Description={{en|A standard kilogram weight kept by the National Institute of Standards and Technology, USA, one of two which serve a

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