Chromium | Wikipedia audio article
Channel: wikipedia tts
Date: 31/01/2019

This is an audio version of the Wikipedia Article:
https://en.wikipedia.org/wiki/Chromium


00:01:59 1 Physical properties
00:02:09 1.1 Atomic
00:05:51 1.2 Bulk
00:05:59 1.2.1 Passivation
00:07:14 1.3 Isotopes
00:08:10 2 Chemistry and compounds
00:09:29 2.1 Chemical properties
00:09:39 2.2 Primary oxidation states
00:09:53 2.2.1 Chromium(III)
00:10:34 2.2.2 Chromium(VI)
00:10:45 2.3 Other oxidation states
00:12:57 2.3.1 Chromium(V) and chromium(IV)
00:15:29 2.3.2 Chromium(II)
00:15:39 2.3.3 Chromium(I)
00:17:13 2.3.4 Chromium(0)
00:18:04 3 Occurrence
00:18:44 4 History
00:19:05 4.1 Ancient uses
00:19:29 4.1.1 Terracotta Army weapons
00:19:38 4.2 Chromium as pigment
00:20:25 5 Production
00:21:20 6 Applications
00:23:49 6.1 Metallurgy
00:26:15 6.2 Dye and pigment
00:26:38 6.2.1 Synthetic ruby and the first laser
00:29:48 6.3 Wood preservative
00:32:10 6.4 Tanning
00:33:01 6.5 Refractory material
00:33:46 6.6 Catalysts
00:34:36 6.7 Other uses
00:35:16 7 Biological role
00:35:50 7.1 Dietary recommendations
00:37:29 7.2 Food sources
00:39:27 7.3 Supplementation
00:42:59 7.3.1 Approved and disapproved health claims
00:43:58 7.3.2 Diabetes
00:45:09 7.3.3 Weight management
00:46:47 7.3.4 Athletic performance
00:48:00 7.4 Fresh-water fish
00:49:00 8 Precautions
00:49:47 8.1 Chromium(VI) toxicity
00:51:55 8.2 Environmental issues
00:53:14 9 See also
00:55:31 10 Notes
00:56:24 11 References



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SUMMARY
=======
Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard and brittle transition metal. Chromium boasts a high usage rate as a metal that is able to be highly polished while resisting tarnishing. Chromium is also the main component of stainless steel, a popular steel alloy due to its uncommonly high specular reflection. Simple polished chromium reflects almost 70% of the visible spectrum, with almost 90% of infrared light waves being reflected. The name of the element is derived from the Greek word χρῶμα, chrōma, meaning color, because many chromium compounds are intensely colored.
Ferrochromium alloy is commercially produced from chromite by silicothermic or aluminothermic reactions and chromium metal by roasting and leaching processes followed by reduction with carbon and then aluminium. Chromium metal is of high value for its high corrosion resistance and hardness. A major development in steel production was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating (electroplating with chromium) together comprise 85% of the commercial use.
In the United States, trivalent chromium (Cr(III)) ion is considered an essential nutrient in humans for insulin, sugar and lipid metabolism. However, in 2014, the European Food Safety Authority, acting for the European Union, concluded that there was not sufficient evidence for chromium to be recognized as essential.While chromium metal and Cr(III) ions are not considered toxic, hexavalent chromium (Cr(VI)) is both toxic and carcinogenic. Abandoned chromium production sites often require environmental cleanup.