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aqua regia

aqua regia [Lat.,=royal water], corrosive, fuming yellow liquid prepared by mixing one volume of concentrated nitric acid with three to four volumes of concentrated hydrochloric acid. It was so named by the alchemists because it dissolves gold and platinum, the "royal" metals, which do not dissolve in nitric or hydrochloric acid alone. Its fumes and yellow color are caused by reaction of nitric acid, HNO ₃ , with hydrogen chloride, HCl, to form nitrosyl chloride, NOCl, chlorine, Cl ₂ , and water; both chlorine and nitrosyl chloride are yellow-colored and volatile. The nitrosyl chloride further decomposes to nitric oxide, NO, and chlorine. Nitric acid is a powerful oxidizing agent (see oxidation and reduction ), but the chemical equilibrium for its reaction with gold, Au, only permits formation of a tiny amount of Au ⁺³ ion, so the amount of gold dissolved in pure nitric acid is undetectable. The presence of chloride ion, Cl ^- , allows formation of the stable chloraurate complex ion , AuCl ₄^- . Because of the high concentration of chloride ion in aqua regia, the Au ⁺³ is reacted almost as soon as it is formed, keeping its concentration low; this allows oxidation of more Au to Au ⁺³ , and the gold is dissolved. The gold may also react directly with the free chlorine in aqua regia, since chlorine is a powerful oxidizing agent.

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	How can nitric acid producer manage itself?(Inorganics) Magazine article from: China Chemical Reporter; 2/6/2008; 700+ words ; ...increase, the price of concentrated nitric acid went down in the golden sales season...brisk sales period for concentrated nitric acid. (b) The negative impact of capacity...basis of these support factors that nitric acid producers who had suffered loss in 2005... Read more
	Concentrated nitric acid demand increases steadily. Magazine article from: China Chemical Reporter; 5/26/2006; ; 700+ words ; ...output There are around 40 concentrated nitric acid producers in China today with a total...expected that the capacity of concentrated nitric acid in China will still increase at an annual...has the largest output of concentrated nitric acid. The output of concentrated nitric ... Read more
	Nitric acid price anomalies.(Inorganics) Magazine article from: China Chemical Reporter; 8/26/2008; ; 700+ words ; The price of concentrated nitric acid in the domestic market increased drastically...two years ago when the concentrated nitric acid market in China was slack. Ups and downs of concentrated nitric acid prices reflect the market for a large... Read more
	Sustained demand increase of concentrated nitric acid.(MARKET REPORT: Inorganics) Magazine article from: China Chemical Reporter; 5/6/2005; ; 700+ words ; Nitric Acid is an important Inorganic chemical raw...Production The output of concentrated nitric acid in China continued to maintain the trend...that of 2003. The output of concentrated nitric acid was 1.2646 million tons in 2004, an increase... Read more
	Price of concentrated nitric acid will gradually stabilize.(Inorganics) Magazine article from: China Chemical Reporter; 5/16/2009; ; 700+ words ; At present, most of the concentrated nitric acid expansion projects constructed in recent...prices. In 2008, China's concentrated nitric acid output was 1.84 million tons, down 6...in 2008 In 2008, China's concentrated nitric acid production capacity was 2.5 million... Read more
	Concentrated nitric acid market: basic supply and demand balance in future. (Inorganics).(Illustration)(Industry Overview) Magazine article from: China Chemical Reporter; 5/16/2003; ; 700+ words ; ...production The production of concentrated nitric acid has developed rapidly in recent years...of China, the output of concentrated nitric acid was 991 200 tons in 2002, an increase...competitiveness, a new 100 000 t/a concentrated nitric acid unit in Jinan Chemical Fertilizer Plant... Read more
	100 000 t/a concentrated nitric acid unit come on stream in Anhui.(Anhui Huaihua Group Company Ltd. starts production)(Brief article) Magazine article from: China Chemical Reporter; 8/16/2006; 126 words ; The 100 000 t/a concentrated nitric acid unit in Anhui Huaihua Group Co., Ltd. with...produced qualified products. The concentration of nitric acid reached more than 98%. The dilute nitric acid unit partially uses the dual-pressure process... Read more
	100 000 t/a nitric acid renovation project launched.(Brief Article) Magazine article from: China Chemical Reporter; 6/16/2005; 152 words ; The 100 000 t/a nitric acid renovation project in Anhui Huaihua...project, the capacity of concentrated nitric acid in the company can reach 330 000...expansions conducted to the concentrated nitric acid unit, the capacity of concentrated... Read more
	Nanjing to build up diluent nitric acid apparatuses. (Newsdesk: Brief).(Brief Article) Magazine article from: China Chemical Reporter; 1/6/2003; 60 words ; ...recently made a decision to establish a set of diluent nitric acid production units, having an annual capacity of 105 thousand tons of diluent nitric acid with the most advanced nitric acid technology domestically. The project has passed the... Read more
	Nitric acid unit launched in Nanjing.(Nanjing Chemical Co. Ltd)(Brief article) Magazine article from: China Chemical Reporter; 6/6/2006; 190 words ; The 270 000 t/a dilute nitric acid unit using the dual-pressure process...province. The company owns 3 old nitric acid production units. Two of them use...standard. The 270 000 t/a dilute nitric acid unit is a project for the optimization... Read more

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	Osmium (revised) Book article from: Chemical Elements: From Carbon to Krypton ...when platinum was dissolved in aqua regia. Aqua regia is a mixture of hydrochloric and nitric acids. The term aqua regia means "royal water." It often...Osmium is dissolved by acids or by aqua regia only after long periods of exposure... Read more
	Platinum Book article from: Chemistry: Foundations and Applications ...deposits and in association with copper, iron, and nickel sulfide ores. The metal is soluble in aqua regia, isolated as (NH 4 ) 2 PtCl 6 from aqua regia, and obtained as a sponge or powder by ignition of (NH 4 ) 2 PtCl 6 . Platinum is used as a catalyst... Read more
	Osmium Book article from: Chemistry: Foundations and Applications ...chemist Smithson Tennant (1761 – 1815) in the black residue that remained after crude platinum was dissolved in aqua regia. The average abundance in Earth's crust is very low, about 0.005 grams (0.00018 ounces) per metric ton, and only four... Read more
	Rhodium Book article from: Chemistry: Foundations and Applications ...purification requires its separation from other platinum metals . Treatment of a crude platinum metal concentrate with aqua regia leaves an insoluble portion that is then fused with bisulfate; this dissolves only the rhodium component, which is eventually... Read more
	platinum Book article from: The Columbia Encyclopedia, Sixth Edition ...with a face-centered cubic crystalline structure. Chemically inactive, it is unaffected by common acids but dissolves in aqua regia , forming chloroplatinic acid (H 2 PtCl 6 ). It is attacked by the halogens, sulfur, or caustic alkalies. It does not... Read more

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