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96-452: The Oquirrh Mountains have been mined for gold , silver , lead , and most famously for copper , as home of the porphyry copper deposit at Bingham Canyon Mine , one of the world's largest open pit mines . As seen from Salt Lake City , the view of the mountain range is dominated by the displaced rock material (known as overburden ) dug from the Kennecott mine. At the north end of the range

192-399: A fault . Water often lubricates faults, filling in fractures and jogs. About 10 kilometres (6.2 mi) below the surface, under very high temperatures and pressures, the water carries high concentrations of carbon dioxide, silica, and gold. During an earthquake, the fault jog suddenly opens wider. The water inside the void instantly vaporizes, flashing to steam and forcing silica, which forms

288-434: A solid solution series with the native element silver (as in electrum ), naturally alloyed with other metals like copper and palladium , and mineral inclusions such as within pyrite . Less commonly, it occurs in minerals as gold compounds, often with tellurium ( gold tellurides ). Gold is resistant to most acids, though it does dissolve in aqua regia (a mixture of nitric acid and hydrochloric acid ), forming

384-660: A 3:8 stoichiometry: The nitric oxide produced may react with atmospheric oxygen to give nitrogen dioxide . With more concentrated nitric acid, nitrogen dioxide is produced directly in a reaction with 1:4 stoichiometry: Upon reaction with nitric acid, most metals give the corresponding nitrates . Some metalloids and metals give the oxides ; for instance, Sn , As , Sb , and Ti are oxidized into SnO 2 , As 2 O 5 , Sb 2 O 5 , and TiO 2 respectively. Some precious metals , such as pure gold and platinum-group metals do not react with nitric acid, though pure gold does react with aqua regia ,

480-410: A base with respect to an acid such as sulfuric acid : The nitronium ion , [NO 2 ] , is the active reagent in aromatic nitration reactions. Since nitric acid has both acidic and basic properties, it can undergo an autoprotolysis reaction, similar to the self-ionization of water : Nitric acid reacts with most metals, but the details depend on the concentration of the acid and the nature of

576-415: A compartment for the carbon anode around which the nitric acid is formed. Nitric acid was pumped out from an earthenware pipe that was sunk down to the bottom of the pot. Fresh water was pumped into the top through another earthenware pipe to replace the fluid removed. The interior was filled with coke . Cast iron cathodes were sunk into the peat surrounding it. Resistance was about 3 ohms per cubic meter and

672-441: A concentration of 68% HNO 3 . This solution has a boiling temperature of 120.5 °C (249 °F) at 1 atm. It is known as "concentrated nitric acid". The azeotrope of nitric acid and water is a colourless liquid at room temperature. Two solid hydrates are known: the monohydrate HNO 3 ·H 2 O or oxonium nitrate [H 3 O] [NO 3 ] and the trihydrate HNO 3 ·3H 2 O . An older density scale

768-436: A density of 1.50 g/cm . This grade is often used in the explosives industry. It is not as volatile nor as corrosive as the anhydrous acid and has the approximate concentration of 21.4 M. Red fuming nitric acid , or RFNA, contains substantial quantities of dissolved nitrogen dioxide ( NO 2 ) leaving the solution with a reddish-brown color. Due to the dissolved nitrogen dioxide, the density of red fuming nitric acid

864-483: A dilute solution of gold(III) chloride or chlorauric acid . Unlike sulfur, phosphorus reacts directly with gold at elevated temperatures to produce gold phosphide (Au 2 P 3 ). Gold readily dissolves in mercury at room temperature to form an amalgam , and forms alloys with many other metals at higher temperatures. These alloys can be produced to modify the hardness and other metallurgical properties, to control melting point or to create exotic colors. Gold

960-465: A few are stable enough to be used in munitions and demolition, while others are still more stable and used as synthetic dyes and medicines (e.g metronidazole ). Nitric acid is also commonly used as a strong oxidizing agent . The discovery of mineral acids such as nitric acid is generally believed to go back to 13th-century European alchemy . The conventional view is that nitric acid was first described in pseudo-Geber 's De inventione veritatis ("On

1056-572: A gold-from-seawater swindle in the United States in the 1890s, as did an English fraudster in the early 1900s. Fritz Haber did research on the extraction of gold from sea water in an effort to help pay Germany 's reparations following World War I . Based on the published values of 2 to 64 ppb of gold in seawater, a commercially successful extraction seemed possible. After analysis of 4,000 water samples yielding an average of 0.004 ppb, it became clear that extraction would not be possible, and he ended

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1152-830: A golden hue to metallic caesium . Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are also important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police and other badges . Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold . Blue gold can be made by alloying with iron , and purple gold can be made by alloying with aluminium . Less commonly, addition of manganese , indium , and other elements can produce more unusual colors of gold for various applications. Colloidal gold , used by electron-microscopists,

1248-552: A large alluvial deposit. The mines at Roşia Montană in Transylvania were also very large, and until very recently, still mined by opencast methods. They also exploited smaller deposits in Britain , such as placer and hard-rock deposits at Dolaucothi . The various methods they used are well described by Pliny the Elder in his encyclopedia Naturalis Historia written towards the end of

1344-429: A mixture of concentrated nitric acid and hydrochloric acid . However, some less noble metals ( Ag , Cu , ...) present in some gold alloys relatively poor in gold such as colored gold can be easily oxidized and dissolved by nitric acid, leading to colour changes of the gold-alloy surface. Nitric acid is used as a cheap means in jewelry shops to quickly spot low-gold alloys (< 14 karats ) and to rapidly assess

1440-462: A novel type of metal-halide perovskite material consisting of Au and Au cations in its crystal structure has been found. It has been shown to be unexpectedly stable at normal conditions. Gold pentafluoride , along with its derivative anion, AuF − 6 , and its difluorine complex , gold heptafluoride , is the sole example of gold(V), the highest verified oxidation state. Some gold compounds exhibit aurophilic bonding , which describes

1536-468: A process to obtain nitric acid by distilling potassium nitrate with sulfuric acid. In 1776 Antoine Lavoisier cited Joseph Priestley 's work to point out that it can be converted from nitric oxide (which he calls "nitrous air"), "combined with an approximately equal volume of the purest part of common air, and with a considerable quantity of water." In 1785 Henry Cavendish determined its precise composition and showed that it could be synthesized by passing

1632-401: A sheet of 1 square metre (11 sq ft), and an avoirdupois ounce into 28 square metres (300 sq ft). Gold leaf can be beaten thin enough to become semi-transparent. The transmitted light appears greenish-blue because gold strongly reflects yellow and red. Such semi-transparent sheets also strongly reflect infrared light, making them useful as infrared (radiant heat) shields in

1728-423: A soluble tetrachloroaurate anion . Gold is insoluble in nitric acid alone, which dissolves silver and base metals , a property long used to refine gold and confirm the presence of gold in metallic substances, giving rise to the term ' acid test '. Gold dissolves in alkaline solutions of cyanide , which are used in mining and electroplating . Gold also dissolves in mercury , forming amalgam alloys, and as

1824-517: A solution of Au(OH) 3 in concentrated H 2 SO 4 produces red crystals of gold(II) sulfate , Au 2 (SO 4 ) 2 . Originally thought to be a mixed-valence compound, it has been shown to contain Au 4+ 2 cations, analogous to the better-known mercury(I) ion, Hg 2+ 2 . A gold(II) complex, the tetraxenonogold(II) cation, which contains xenon as a ligand, occurs in [AuXe 4 ](Sb 2 F 11 ) 2 . In September 2023,

1920-479: A stream of electric sparks through moist air . In 1806, Humphry Davy reported the results of extensive distilled water electrolysis experiments concluding that nitric acid was produced at the anode from dissolved atmospheric nitrogen gas. He used a high voltage battery and non-reactive electrodes and vessels such as gold electrode cones that doubled as vessels bridged by damp asbestos. The industrial production of nitric acid from atmospheric air began in 1905 with

2016-470: Is Au with a half-life of 2.27 days. Gold's least stable isomer is Au with a half-life of only 7 ns. Au has three decay paths: β decay, isomeric transition , and alpha decay. No other isomer or isotope of gold has three decay paths. The possible production of gold from a more common element, such as lead , has long been a subject of human inquiry, and the ancient and medieval discipline of alchemy often focused on it; however,

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2112-696: Is Au , which decays by proton emission with a half-life of 30 μs. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission , α decay , and β decay . The exceptions are Au , which decays by electron capture, and Au , which decays most often by electron capture (93%) with a minor β decay path (7%). All of gold's radioisotopes with atomic masses above 197 decay by β decay. At least 32 nuclear isomers have also been characterized, ranging in atomic mass from 170 to 200. Within that range, only Au , Au , Au , Au , and Au do not have isomers. Gold's most stable isomer

2208-481: Is 0.76 cP. As it decomposes to NO 2 and water, it obtains a yellow tint. It boils at 83 °C (181 °F). It is usually stored in a glass shatterproof amber bottle with twice the volume of head space to allow for pressure build up, but even with those precautions the bottle must be vented monthly to release pressure. The two terminal N–O bonds are nearly equivalent and relatively short, at 1.20 and 1.21 Å. This can be explained by theories of resonance ;

2304-464: Is Kennecott's smelter complex, which refines ore concentrates from the mine into useful metals. Dark-colored tailings from past metal refining at the complex can be observed from the adjacent freeway, I-80 . The value of the minerals taken from the range has been estimated to far exceed the combined value of those taken in the California, Nevada, and Klondike gold and silver rushes. In the winter months,

2400-648: Is also known, an example of a mixed-valence complex . Gold does not react with oxygen at any temperature and, up to 100 °C, is resistant to attack from ozone: Au + O 2 ⟶ ( no reaction ) {\displaystyle {\ce {Au + O2 ->}}({\text{no reaction}})} Au + O 3 → t < 100 ∘ C ( no reaction ) {\displaystyle {\ce {Au{}+O3->[{} \atop {t<100^{\circ }{\text{C}}}]}}({\text{no reaction}})} Some free halogens react to form

2496-520: Is also used in infrared shielding, the production of colored glass , gold leafing , and tooth restoration . Certain gold salts are still used as anti-inflammatory agents in medicine. Gold is the most malleable of all metals. It can be drawn into a wire of single-atom width, and then stretched considerably before it breaks. Such nanowires distort via the formation, reorientation, and migration of dislocations and crystal twins without noticeable hardening. A single gram of gold can be beaten into

2592-427: Is always richer at the exposed surface of gold-bearing veins, owing to the oxidation of accompanying minerals followed by weathering; and by washing of the dust into streams and rivers, where it collects and can be welded by water action to form nuggets. Gold sometimes occurs combined with tellurium as the minerals calaverite , krennerite , nagyagite , petzite and sylvanite (see telluride minerals ), and as

2688-513: Is attributed to wind-blown dust or rivers. At 10 parts per quadrillion, the Earth's oceans would hold 15,000 tonnes of gold. These figures are three orders of magnitude less than reported in the literature prior to 1988, indicating contamination problems with the earlier data. A number of people have claimed to be able to economically recover gold from sea water , but they were either mistaken or acted in an intentional deception. Prescott Jernegan ran

2784-462: Is for the production of fertilizers . Nitric acid is neutralized with ammonia to give ammonium nitrate . This application consumes 75–80% of the 26 million tonnes produced annually (1987). The other main applications are for the production of explosives, nylon precursors, and specialty organic compounds. In organic synthesis , industrial and otherwise, the nitro group is a versatile functional group . A mixture of nitric and sulfuric acids introduces

2880-464: Is found in ores in rock formed from the Precambrian time onward. It most often occurs as a native metal , typically in a metal solid solution with silver (i.e. as a gold/silver alloy ). Such alloys usually have a silver content of 8–10%. Electrum is elemental gold with more than 20% silver, and is commonly known as white gold . Electrum's color runs from golden-silvery to silvery, dependent upon

2976-469: Is home to a trail administered by Salt Lake County and numerous gated communities. Butterfield Canyon contains a paved road (with the exception of a 1/4 mile portion on the Tooele side that is well-maintained dirt) that connects Tooele with Herriman . Butterfield Canyon road climbs to a summit of 9,180 ft. above sea level. At night the mouth of the canyon is a dangerous area as large herds of deer move into

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3072-420: Is lower at 1.490 g/cm . An inhibited fuming nitric acid, either white inhibited fuming nitric acid (IWFNA), or red inhibited fuming nitric acid (IRFNA), can be made by the addition of 0.6 to 0.7% hydrogen fluoride (HF). This fluoride is added for corrosion resistance in metal tanks. The fluoride creates a metal fluoride layer that protects the metal. White fuming nitric acid, pure nitric acid or WFNA,

3168-465: Is most often called the oldest since this treasure is the largest and most diverse. Gold artifacts probably made their first appearance in Ancient Egypt at the very beginning of the pre-dynastic period, at the end of the fifth millennium BC and the start of the fourth, and smelting was developed during the course of the 4th millennium; gold artifacts appear in the archeology of Lower Mesopotamia during

3264-528: Is now questioned. The gold-bearing Witwatersrand rocks were laid down between 700 and 950 million years before the Vredefort impact. These gold-bearing rocks had furthermore been covered by a thick layer of Ventersdorp lavas and the Transvaal Supergroup of rocks before the meteor struck, and thus the gold did not actually arrive in the asteroid/meteorite. What the Vredefort impact achieved, however,

3360-495: Is occasionally seen, with concentrated nitric acid specified as 42  Baumé . Nitric acid is subject to thermal or light decomposition and for this reason it was often stored in brown glass bottles: This reaction may give rise to some non-negligible variations in the vapor pressure above the liquid because the nitrogen oxides produced dissolve partly or completely in the acid. The nitrogen dioxide ( NO 2 ) and/or dinitrogen tetroxide ( N 2 O 4 ) remains dissolved in

3456-427: Is red if the particles are small; larger particles of colloidal gold are blue. Gold has only one stable isotope , Au , which is also its only naturally occurring isotope, so gold is both a mononuclidic and monoisotopic element . Thirty-six radioisotopes have been synthesized, ranging in atomic mass from 169 to 205. The most stable of these is Au with a half-life of 186.1 days. The least stable

3552-471: Is referred to as fuming nitric acid . Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%. Nitric acid is the primary reagent used for nitration – the addition of a nitro group , typically to an organic molecule . While some resulting nitro compounds are shock- and thermally-sensitive explosives ,

3648-484: Is similarly unaffected by most bases. It does not react with aqueous , solid , or molten sodium or potassium hydroxide . It does however, react with sodium or potassium cyanide under alkaline conditions when oxygen is present to form soluble complexes. Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduced and precipitated as metal by adding any other metal as

3744-430: Is the proper conditions under which anhydrous ammonia burns to nitric oxide (NO) instead of dinitrogen ( N 2 ). The nitric oxide is then oxidized, often with atmospheric oxygen , to nitrogen dioxide ( NO 2 ): The dioxide then disproportionates in water to nitric acid and the nitric oxide feedstock: The net reaction is maximal oxidation of ammonia: Dissolved nitrogen oxides are either stripped (in

3840-585: Is the soluble form of gold encountered in mining. The binary gold halides , such as AuCl , form zigzag polymeric chains, again featuring linear coordination at Au. Most drugs based on gold are Au(I) derivatives. Au(III) (referred to as auric) is a common oxidation state, and is illustrated by gold(III) chloride , Au 2 Cl 6 . The gold atom centers in Au(III) complexes, like other d compounds, are typically square planar , with chemical bonds that have both covalent and ionic character. Gold(I,III) chloride

3936-634: Is thought to have been delivered to Earth by asteroid impacts during the Late Heavy Bombardment , about 4 billion years ago. Gold which is reachable by humans has, in one case, been associated with a particular asteroid impact. The asteroid that formed Vredefort impact structure 2.020 billion years ago is often credited with seeding the Witwatersrand basin in South Africa with the richest gold deposits on earth. However, this scenario

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4032-505: Is thought to have been produced in supernova nucleosynthesis , and from the collision of neutron stars , and to have been present in the dust from which the Solar System formed. Traditionally, gold in the universe is thought to have formed by the r-process (rapid neutron capture) in supernova nucleosynthesis , but more recently it has been suggested that gold and other elements heavier than iron may also be produced in quantity by

4128-416: Is unaffected by most acids. It does not react with hydrofluoric , hydrochloric , hydrobromic , hydriodic , sulfuric , or nitric acid . It does react with selenic acid , and is dissolved by aqua regia , a 1:3 mixture of nitric acid and hydrochloric acid . Nitric acid oxidizes the metal to +3 ions, but only in minute amounts, typically undetectable in the pure acid because of the chemical equilibrium of

4224-475: Is very close to anhydrous nitric acid. It is available as 99.9% nitric acid by assay, or about 24  molar . One specification for white fuming nitric acid is that it has a maximum of 2% water and a maximum of 0.5% dissolved NO 2 . Anhydrous nitric acid is a colorless, low- viscosity (mobile) liquid with a density of 1.512–3 g/cm that solidifies at −42 °C (−44 °F) to form white crystals. Its dynamic viscosity under standard conditions

4320-401: The Ṣundūq al-ḥikma attributed to Jabir has been translated as follows: Take five parts of pure flowers of nitre , three parts of Cyprus vitriol and two parts of Yemen alum . Powder them well, separately, until they are like dust and then place them in a flask. Plug the latter with a palm fibre and attach a glass receiver to it. Then invert the apparatus and heat the upper portion (i.e.

4416-483: The Birkeland–Eyde process , also known as the arc process. This process is based upon the oxidation of atmospheric nitrogen by atmospheric oxygen to nitric oxide with a very high temperature electric arc. Yields of up to approximately 4–5% nitric oxide were obtained at 3000 °C, and less at lower temperatures. The nitric oxide was cooled and oxidized by the remaining atmospheric oxygen to nitrogen dioxide, and this

4512-645: The Chu (state) circulated the Ying Yuan , one kind of square gold coin. In Roman metallurgy , new methods for extracting gold on a large scale were developed by introducing hydraulic mining methods, especially in Hispania from 25 BC onwards and in Dacia from 106 AD onwards. One of their largest mines was at Las Medulas in León , where seven long aqueducts enabled them to sluice most of

4608-583: The Old Testament , starting with Genesis 2:11 (at Havilah ), the story of the golden calf , and many parts of the temple including the Menorah and the golden altar. In the New Testament , it is included with the gifts of the magi in the first chapters of Matthew. The Book of Revelation 21:21 describes the city of New Jerusalem as having streets "made of pure gold, clear as crystal". Exploitation of gold in

4704-641: The Varna Necropolis near Lake Varna and the Black Sea coast, thought to be the earliest "well-dated" finding of gold artifacts in history. Several prehistoric Bulgarian finds are considered no less old – the golden treasures of Hotnitsa, Durankulak , artifacts from the Kurgan settlement of Yunatsite near Pazardzhik , the golden treasure Sakar, as well as beads and gold jewelry found in the Kurgan settlement of Provadia – Solnitsata ("salt pit"). However, Varna gold

4800-567: The chemical symbol Au (from Latin aurum ) and atomic number 79. In its pure form, it is a bright , slightly orange-yellow, dense, soft, malleable , and ductile metal . Chemically, gold is a transition metal , a group 11 element , and one of the noble metals . It is one of the least reactive chemical elements, being the second-lowest in the reactivity series . It is solid under standard conditions . Gold often occurs in free elemental ( native state ), as nuggets or grains, in rocks , veins , and alluvial deposits . It occurs in

4896-470: The reducing agent . The added metal is oxidized and dissolves, allowing the gold to be displaced from solution and be recovered as a solid precipitate. Less common oxidation states of gold include −1, +2, and +5. The −1 oxidation state occurs in aurides, compounds containing the Au anion . Caesium auride (CsAu), for example, crystallizes in the caesium chloride motif; rubidium, potassium, and tetramethylammonium aurides are also known. Gold has

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4992-551: The Discovery of Truth", after c.  1300 ). However, according to Eric John Holmyard and Ahmad Y. al-Hassan , the nitric acid also occurs in various earlier Arabic works such as the Ṣundūq al-ḥikma ("Chest of Wisdom") attributed to Jabir ibn Hayyan (8th century) or the Taʿwīdh al-Ḥākim attributed to the Fatimid caliph al-Hakim bi-Amr Allah (985–1021). The recipe in

5088-498: The N–OH single bond. Nitric acid is normally considered to be a strong acid at ambient temperatures. There is some disagreement over the value of the acid dissociation constant, though the p K a value is usually reported as less than −1. This means that the nitric acid in diluted solution is fully dissociated except in extremely acidic solutions. The p K a value rises to 1 at a temperature of 250 °C. Nitric acid can act as

5184-525: The acid, but the last plant in the United States ceased using that process in 2012. More recently, electrochemical means have been developed to produce anhydrous acid from concentrated nitric acid feedstock. Laboratory-scale nitric acid syntheses abound. Most take inspiration from the industrial techniques. A wide variety of nitrate salts metathesize with sulfuric acid ( H 2 SO 4 ) — for example, sodium nitrate : Distillation at nitric acid's 83 °C boiling point then separates

5280-637: The byproducts removed to isolate the desired product. Reaction with non-metallic elements, with the exceptions of nitrogen, oxygen, noble gases , silicon , and halogens other than iodine, usually oxidizes them to their highest oxidation states as acids with the formation of nitrogen dioxide for concentrated acid and nitric oxide for dilute acid. Concentrated nitric acid oxidizes I 2 , P 4 , and S 8 into HIO 3 , H 3 PO 4 , and H 2 SO 4 , respectively. Although it reacts with graphite and amorphous carbon, it does not react with diamond; it can separate diamond from

5376-420: The case of white fuming nitric acid) or remain in solution to form red fuming nitric acid . Commercial grade nitric acid solutions are usually between 52% and 68% nitric acid by mass, the maximum distillable concentration . Further dehydration to 98% can be achieved with concentrated H 2 SO 4 . Historically, higher acid concentrations were also produced by dissolving additional nitrogen dioxide in

5472-560: The color turns orange. These color changes are caused by nitrated aromatic rings in the protein. Xanthoproteic acid is formed when the acid contacts epithelial cells . Respective local skin color changes are indicative of inadequate safety precautions when handling nitric acid. Industrial nitric acid production uses the Ostwald process . The combined Ostwald and Haber processes are extremely efficient, requiring only air and natural gas feedstocks . The Ostwald process' technical innovation

5568-448: The concentrated acid forms a metal-oxide layer that protects the bulk of the metal from further oxidation. The formation of this protective layer is called passivation . Typical passivation concentrations range from 20% to 50% by volume. Metals that are passivated by concentrated nitric acid are iron , cobalt , chromium , nickel , and aluminium . Being a powerful oxidizing acid , nitric acid reacts with many organic materials, and

5664-1409: The corresponding gold halides. Gold is strongly attacked by fluorine at dull-red heat to form gold(III) fluoride AuF 3 . Powdered gold reacts with chlorine at 180 °C to form gold(III) chloride AuCl 3 . Gold reacts with bromine at 140 °C to form a combination of gold(III) bromide AuBr 3 and gold(I) bromide AuBr, but reacts very slowly with iodine to form gold(I) iodide AuI: 2 Au + 3 F 2 → Δ 2 AuF 3 {\displaystyle {\ce {2Au{}+3F2->[{} \atop \Delta ]2AuF3}}} 2 Au + 3 Cl 2 → Δ 2 AuCl 3 {\displaystyle {\ce {2Au{}+3Cl2->[{} \atop \Delta ]2AuCl3}}} 2 Au + 2 Br 2 → Δ AuBr 3 + AuBr {\displaystyle {\ce {2Au{}+2Br2->[{} \atop \Delta ]AuBr3{}+AuBr}}} 2 Au + I 2 → Δ 2 AuI {\displaystyle {\ce {2Au{}+I2->[{} \atop \Delta ]2AuI}}} Gold does not react with sulfur directly, but gold(III) sulfide can be made by passing hydrogen sulfide through

5760-424: The densest element, osmium , is 22.588 ± 0.015 g/cm . Whereas most metals are gray or silvery white, gold is slightly reddish-yellow. This color is determined by the frequency of plasma oscillations among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to relativistic effects affecting the orbitals around gold atoms. Similar effects impart

5856-664: The early 4th millennium. As of 1990, gold artifacts found at the Wadi Qana cave cemetery of the 4th millennium BC in West Bank were the earliest from the Levant. Gold artifacts such as the golden hats and the Nebra disk appeared in Central Europe from the 2nd millennium BC Bronze Age . The oldest known map of a gold mine was drawn in the 19th Dynasty of Ancient Egypt (1320–1200 BC), whereas

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5952-421: The farmlands for feeding. The north end of the mountain range features a peak known as Farnsworth Peak which houses almost all Salt Lake City FM and TV station transmitters. The peak is also used for emergency communications (such as police , fire , and EMS ). Several local businesses and amateur radio operators have transmitters on Farnsworth Peak. Gold Gold is a chemical element with

6048-431: The first century AD. Nitric acid Nitric acid is an inorganic compound with the formula H N O 3 . It is a highly corrosive mineral acid . The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into oxides of nitrogen . Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% HNO 3 , it

6144-574: The first written reference to gold was recorded in the 12th Dynasty around 1900 BC. Egyptian hieroglyphs from as early as 2600 BC describe gold, which King Tushratta of the Mitanni claimed was "more plentiful than dirt" in Egypt. Egypt and especially Nubia had the resources to make them major gold-producing areas for much of history. One of the earliest known maps, known as the Turin Papyrus Map , shows

6240-488: The flask containing the mixture) with a gentle fire. There will flow down by reason of the heat an oil like cow's butter. Nitric acid is also found in post-1300 works falsely attributed to Albert the Great and Ramon Llull (both 13th century). These works describe the distillation of a mixture containing niter and green vitriol , which they call "eau forte" (aqua fortis). In the 17th century, Johann Rudolf Glauber devised

6336-419: The formation of nitrogen dioxide ( NO 2 ). However, the powerful oxidizing properties of nitric acid are thermodynamic in nature, but sometimes its oxidation reactions are rather kinetically non-favored. The presence of small amounts of nitrous acid ( HNO 2 ) greatly increases the rate of reaction. Although chromium (Cr), iron (Fe), and aluminium (Al) readily dissolve in dilute nitric acid,

6432-403: The gold acts simply as a solute, this is not a chemical reaction . A relatively rare element, gold is a precious metal that has been used for coinage , jewelry , and other works of art throughout recorded history . In the past, a gold standard was often implemented as a monetary policy . Gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard

6528-430: The gold purity. Being a powerful oxidizing agent, nitric acid reacts with many non-metallic compounds, sometimes explosively. Depending on the acid concentration, temperature and the reducing agent involved, the end products can be variable. Reaction takes place with all metals except the noble metals series and certain alloys . As a general rule, oxidizing reactions occur primarily with the concentrated acid, favoring

6624-417: The graphite that it oxidizes. Nitric acid reacts with proteins to form yellow nitrated products. This reaction is known as the xanthoproteic reaction . This test is carried out by adding concentrated nitric acid to the substance being tested, and then heating the mixture. If proteins that contain amino acids with aromatic rings are present, the mixture turns yellow. Upon adding a base such as ammonia ,

6720-563: The highest electron affinity of any metal, at 222.8 kJ/mol, making Au a stable species, analogous to the halides . Gold also has a –1 oxidation state in covalent complexes with the group 4 transition metals, such as in titanium tetraauride and the analogous zirconium and hafnium compounds. These chemicals are expected to form gold-bridged dimers in a manner similar to titanium(IV) hydride . Gold(II) compounds are usually diamagnetic with Au–Au bonds such as [ Au(CH 2 ) 2 P(C 6 H 5 ) 2 ] 2 Cl 2 . The evaporation of

6816-422: The metal. Dilute nitric acid behaves as a typical acid in its reaction with most metals. Magnesium , manganese , and zinc liberate H 2 : Nitric acid can oxidize non-active metals such as copper and silver . With these non-active or less electropositive metals the products depend on temperature and the acid concentration. For example, copper reacts with dilute nitric acid at ambient temperatures with

6912-542: The mineral quartz, and gold out of the fluids and onto nearby surfaces. The world's oceans contain gold. Measured concentrations of gold in the Atlantic and Northeast Pacific are 50–150 femtomol /L or 10–30 parts per quadrillion (about 10–30 g/km ). In general, gold concentrations for south Atlantic and central Pacific samples are the same (~50 femtomol/L) but less certain. Mediterranean deep waters contain slightly higher concentrations of gold (100–150 femtomol/L), which

7008-473: The mountains become home to a small population of bald eagles , which can often be found in the cliffs on the west side of the range down to the reservoir near the town of Stockton . The range has many canyons and dense forests, consisting mainly of conifers and aspen. The area is also home to thriving populations of butterflies, deer, mountain lions, and squirrels. Two of the most popular canyons are Yellow Fork Canyon and Butterfield Canyon . Yellow Fork Canyon

7104-427: The nitric acid coloring it yellow or even red at higher temperatures. While the pure acid tends to give off white fumes when exposed to air, acid with dissolved nitrogen dioxide gives off reddish-brown vapors, leading to the common names "red fuming nitric acid" and "white fuming nitric acid". Nitrogen oxides ( NO x ) are soluble in nitric acid. Commercial-grade fuming nitric acid contains 98% HNO 3 and has

7200-411: The noble metals, it still forms many diverse compounds. The oxidation state of gold in its compounds ranges from −1 to +5, but Au(I) and Au(III) dominate its chemistry. Au(I), referred to as the aurous ion, is the most common oxidation state with soft ligands such as thioethers , thiolates , and organophosphines . Au(I) compounds are typically linear. A good example is Au(CN) − 2 , which

7296-563: The plan of a gold mine in Nubia together with indications of the local geology . The primitive working methods are described by both Strabo and Diodorus Siculus , and included fire-setting . Large mines were also present across the Red Sea in what is now Saudi Arabia . Gold is mentioned in the Amarna letters numbered 19 and 26 from around the 14th century BC. Gold is mentioned frequently in

7392-522: The power supplied was around 10 volts. Production from one deposit was 800 tons per year. Once the Haber process for the efficient production of ammonia was introduced in 1913, nitric acid production from ammonia using the Ostwald process overtook production from the Birkeland–Eyde process. This method of production is still in use today. Commercially available nitric acid is an azeotrope with water at

7488-459: The project. The earliest recorded metal employed by humans appears to be gold, which can be found free or " native ". Small amounts of natural gold have been found in Spanish caves used during the late Paleolithic period, c.  40,000 BC . The oldest gold artifacts in the world are from Bulgaria and are dating back to the 5th millennium BC (4,600 BC to 4,200 BC), such as those found in

7584-681: The r-process in the collision of neutron stars . In both cases, satellite spectrometers at first only indirectly detected the resulting gold. However, in August 2017, the spectroscopic signatures of heavy elements, including gold, were observed by electromagnetic observatories in the GW170817 neutron star merger event, after gravitational wave detectors confirmed the event as a neutron star merger. Current astrophysical models suggest that this single neutron star merger event generated between 3 and 13 Earth masses of gold. This amount, along with estimations of

7680-620: The rare bismuthide maldonite ( Au 2 Bi ) and antimonide aurostibite ( AuSb 2 ). Gold also occurs in rare alloys with copper , lead , and mercury : the minerals auricupride ( Cu 3 Au ), novodneprite ( AuPb 3 ) and weishanite ( (Au,Ag) 3 Hg 2 ). A 2004 research paper suggests that microbes can sometimes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits. A 2013 study has claimed water in faults vaporizes during an earthquake, depositing gold. When an earthquake strikes, it moves along

7776-420: The rate of occurrence of these neutron star merger events, suggests that such mergers may produce enough gold to account for most of the abundance of this element in the universe. Because the Earth was molten when it was formed , almost all of the gold present in the early Earth probably sank into the planetary core . Therefore, as hypothesized in one model, most of the gold in the Earth's crust and mantle

7872-935: The reaction. However, the ions are removed from the equilibrium by hydrochloric acid, forming AuCl − 4 ions, or chloroauric acid , thereby enabling further oxidation: 2 Au + 6 H 2 SeO 4 → 200 ∘ C Au 2 ( SeO 4 ) 3 + 3 H 2 SeO 3 + 3 H 2 O {\displaystyle {\ce {2Au{}+6H2SeO4->[{} \atop {200^{\circ }{\text{C}}}]Au2(SeO4)3{}+3H2SeO3{}+3H2O}}} Au + 4 HCl + HNO 3 ⟶ HAuCl 4 + NO ↑ + 2 H 2 O {\displaystyle {\ce {Au{}+4HCl{}+HNO3->HAuCl4{}+NO\uparrow +2H2O}}} Gold

7968-456: The reactions may be explosive. The hydroxyl group will typically strip a hydrogen from the organic molecule to form water, and the remaining nitro group takes the hydrogen's place. Nitration of organic compounds with nitric acid is the primary method of synthesis of many common explosives, such as nitroglycerin and trinitrotoluene (TNT). As very many less stable byproducts are possible, these reactions must be carefully thermally controlled, and

8064-464: The rest of the gold on Earth is thought to have been incorporated into the planet since its very beginning, as planetesimals formed the mantle . In 2017, an international group of scientists established that gold "came to the Earth's surface from the deepest regions of our planet", the mantle, as evidenced by their findings at Deseado Massif in the Argentinian Patagonia . On Earth, gold

8160-474: The same result and showing that the isotopes of gold produced by it were all radioactive . In 1980, Glenn Seaborg transmuted several thousand atoms of bismuth into gold at the Lawrence Berkeley Laboratory. Gold can be manufactured in a nuclear reactor, but doing so is highly impractical and would cost far more than the value of the gold that is produced. Although gold is the most noble of

8256-486: The silver content. The more silver, the lower the specific gravity . Native gold occurs as very small to microscopic particles embedded in rock, often together with quartz or sulfide minerals such as " fool's gold ", which is a pyrite . These are called lode deposits. The metal in a native state is also found in the form of free flakes, grains or larger nuggets that have been eroded from rocks and end up in alluvial deposits called placer deposits . Such free gold

8352-467: The solid metal-salt residue. The resulting acid solution is the 68.5% azeotrope, and can be further concentrated (as in industry) with either sulfuric acid or magnesium nitrate . Alternatively, thermal decomposition of copper(II) nitrate gives nitrogen dioxide and oxygen gases; these are then passed through water or hydrogen peroxide as in the Ostwald process: The main industrial use of nitric acid

8448-446: The south-east corner of the Black Sea is said to date from the time of Midas , and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia around 610 BC. The legend of the golden fleece dating from eighth century BCE may refer to the use of fleeces to trap gold dust from placer deposits in the ancient world. From the 6th or 5th century BC,

8544-436: The tendency of gold ions to interact at distances that are too long to be a conventional Au–Au bond but shorter than van der Waals bonding . The interaction is estimated to be comparable in strength to that of a hydrogen bond . Well-defined cluster compounds are numerous. In some cases, gold has a fractional oxidation state. A representative example is the octahedral species {Au( P(C 6 H 5 ) 3 )} 2+ 6 . Gold

8640-403: The transmutation of the chemical elements did not become possible until the understanding of nuclear physics in the 20th century. The first synthesis of gold was conducted by Japanese physicist Hantaro Nagaoka , who synthesized gold from mercury in 1924 by neutron bombardment. An American team, working without knowledge of Nagaoka's prior study, conducted the same experiment in 1941, achieving

8736-449: The two major canonical forms show some double bond character in these two bonds, causing them to be shorter than N–O single bonds . The third N–O bond is elongated because its O atom is bonded to H atom, with a bond length of 1.41 Å in the gas phase. The molecule is slightly aplanar (the NO 2 and NOH planes are tilted away from each other by 2°) and there is restricted rotation about

8832-417: The visors of heat-resistant suits and in sun visors for spacesuits . Gold is a good conductor of heat and electricity . Gold has a density of 19.3 g/cm , almost identical to that of tungsten at 19.25 g/cm ; as such, tungsten has been used in the counterfeiting of gold bars , such as by plating a tungsten bar with gold. By comparison, the density of lead is 11.34 g/cm , and that of

8928-783: Was abandoned for a fiat currency system after the Nixon shock measures of 1971. In 2020, the world's largest gold producer was China, followed by Russia and Australia. As of 2020 , a total of around 201,296 tonnes of gold exist above ground. This is equal to a cube, with each side measuring roughly 21.7 meters (71 ft). The world's consumption of new gold produced is about 50% in jewelry, 40% in investments , and 10% in industry . Gold's high malleability, ductility, resistance to corrosion and most other chemical reactions, as well as conductivity of electricity have led to its continued use in corrosion-resistant electrical connectors in all types of computerized devices (its chief industrial use). Gold

9024-406: Was rapidly displaced by the Ostwald process once cheap ammonia became available. Another early production method was invented by French engineer Albert Nodon around 1913. His method produced nitric acid from electrolysis of calcium nitrate converted by bacteria from nitrogenous matter in peat bogs. An earthenware pot surrounded by limestone was sunk into the peat and staked with tarred lumber to make

9120-407: Was subsequently absorbed in water in a series of packed column or plate column absorption towers to produce dilute nitric acid. The first towers bubbled the nitrogen dioxide through water and non-reactive quartz fragments. About 20% of the produced oxides of nitrogen remained unreacted so the final towers contained an alkali solution to neutralize the rest. The process was very energy intensive and

9216-605: Was to distort the Witwatersrand basin in such a way that the gold-bearing rocks were brought to the present erosion surface in Johannesburg , on the Witwatersrand , just inside the rim of the original 300 km (190 mi) diameter crater caused by the meteor strike. The discovery of the deposit in 1886 launched the Witwatersrand Gold Rush . Some 22% of all the gold that is ascertained to exist today on Earth has been extracted from these Witwatersrand rocks. Much of

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