Colored gold is the name given to any gold that has been treated using techniques to change its natural color. Pure gold is slightly reddish yellow in color, but colored gold can come in a variety of different colors by alloying it with different elements.
78-496: Colored golds can be classified in three groups: Pure 100% (in practice, 99.9% or better) gold is 24 karat by definition, so all colored golds are less pure than this, commonly 18K (75%), 14K (58.5%), 10K (41.6%), or 9K (37.5%). The word white covers a broad range of colors that borders or overlaps pale yellow, tinted brown, and even very pale rose. White gold is an alloy of gold and at least one white metal (usually nickel , silver , platinum or palladium ). Like yellow gold,
156-449: A barrier cream on the hands to prevent absorption through the skin even though the amount of cadmium absorbed into the body through the skin is reported to be less than 1%. In PVC , cadmium was used as heat, light, and weathering stabilizers. Currently, cadmium stabilizers have been completely replaced with barium-zinc, calcium-zinc and organo-tin stabilizers. Cadmium is used in many kinds of solder and bearing alloys, because it has
234-500: A neutron poison , cadmium is also used as a component of control rods in nuclear fission reactors. One of its few new uses is in cadmium telluride solar panels . Although cadmium has no known biological function in higher organisms, a cadmium-dependent carbonic anhydrase has been found in marine diatoms . Cadmium is a soft, malleable , ductile , silvery-white divalent metal. It is similar in many respects to zinc but forms complex compounds. Unlike most other metals, cadmium
312-416: A self-assembled monolayer one can obtain a cadmium selective electrode with a ppt -level sensitivity. Cadmium has no known function in higher organisms and is considered toxic. Cadmium is considered an environmental pollutant hazardous to living organisms. A cadmium-dependent carbonic anhydrase has been found in some marine diatoms , which live in environments with low zinc concentrations. Cadmium
390-456: A black oxide layer with heat treatment at 700–950 °C. Copper, iron and titanium can be also used for such effect. Gold-cobalt-chromium alloy (75% gold, 15% cobalt, 10% chromium) yields a surface oxide that is olive-tinted because of the chromium(III) oxide content, is about five times thinner than Au-Co and has significantly better wear resistance. The gold-cobalt alloy consists of gold-rich (about 94% Au) and cobalt-rich (about 90% Co) phases;
468-505: A cadmium-bearing mixture of minerals that was named after the Greek mythological character Κάδμος, Cadmus , the founder of Thebes ) was discovered in contaminated zinc compounds sold in pharmacies in Germany in 1817 by Friedrich Stromeyer . Karl Samuel Leberecht Hermann simultaneously investigated the discoloration in zinc oxide and found an impurity, first suspected to be arsenic , because of
546-499: A common source of blue or ultraviolet laser light. Lasers at wavelengths of 325, 354 and 442 nm are made using this gain medium ; some models can switch between these wavelengths. They are notably used in fluorescence microscopy as well as various laboratory uses requiring laser light at these wavelengths. Cadmium selenide quantum dots emit bright luminescence under UV excitation (He–Cd laser, for example). The color of this luminescence can be green, yellow or red depending on
624-513: A concern because it would be possible for an unscrupulous refiner to produce precious metals bars that are slightly less pure than marked on the bar. A refiner doing $ 1 billion of business each year that marked .980 pure bars as .999 fine would make about an extra $ 20 million in profit. In the United States, the actual purity of gold articles must be no more than .003 less than the marked purity (e.g. .996 fine for gold marked .999 fine), and
702-508: A few instances of general population poisoning as the result of long-term exposure to cadmium in contaminated food and water. Research into an estrogen mimicry that may induce breast cancer is ongoing, as of 2012 . In the decades leading up to World War II , mining operations contaminated the Jinzū River in Japan with cadmium and traces of other toxic metals. As a consequence, cadmium accumulated in
780-548: A fineness of 11 ounces, 2 pennyweights, or exactly ( 11 + 2 20 ) 12 = 92.5 % {\displaystyle {\frac {(11+{\frac {2}{20}})}{12}}=92.5\%} silver. Cadmium Cadmium is a chemical element ; it has symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 , zinc and mercury . Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has
858-506: A gold plating of the surface, followed by indium plating, with layer thickness matching the 1:2 atomic ratio. A heat treatment then causes interdiffusion of the metals and formation of the required intermetallic compound. Black gold is a type of gold used in jewelry. Black-colored gold can be produced by various methods: A range of colors from brown to black can be achieved on copper-rich alloys by treatment with potassium sulfide . Cobalt-containing alloys, e.g. 75% gold with 25% cobalt, form
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#1732859283483936-487: A gold-copper alloy widely used for specialized jewelry . Rose gold, also known as pink gold and red gold, was popular in Russia at the beginning of the 19th century, and was also known as Russian gold. Rose gold jewelry is becoming more popular in the 21st century, and is commonly used for wedding rings, bracelets, and other jewelry. Although the names are often used interchangeably, the difference between red, rose, and pink gold
1014-460: A green color, but there are health concerns regarding its use, as cadmium is highly toxic . The alloy of 75% gold, 15% silver, 6% copper, and 4% cadmium yields a dark-green alloy. Gray gold alloys are usually made from gold and palladium. A cheaper alternative which does not use palladium is made by adding silver, manganese , and copper to the gold in specific ratios. All the AuX 2 intermetallics have
1092-429: A growing demand for cadmium for nickel–cadmium batteries, which accounted for 81% of the cadmium consumption in the United States in 2006. Cadmium makes up about 0.1 ppm of Earth's crust and is the 65th most abundant element. It is much rarer than zinc, which makes up about 65 ppm. No significant deposits of cadmium-containing ores are known. The only cadmium mineral of importance, greenockite (Cd S ),
1170-560: A half-life of 462.6 days, and Cd with a half-life of 53.46 hours. All of the remaining radioactive isotopes have half-lives of less than 2.5 hours, and the majority have half-lives of less than 5 minutes. Cadmium has 8 known meta states , with the most stable being Cd ( t 1⁄2 = 14.1 years), Cd ( t 1⁄2 = 44.6 days), and Cd ( t 1⁄2 = 3.36 hours). The known isotopes of cadmium range in atomic mass from 94.950 u ( Cd) to 131.946 u ( Cd). For isotopes lighter than 112 u,
1248-409: A less-than-24-karat gold alloy differs according to the alloys used. For example, knowing that standard 18-karat yellow gold consists of 75% gold, 12.5% silver and the remaining 12.5% of copper (all by mass), the volume of pure gold in this alloy will be 60% since gold is much denser than the other metals used: 19.32 g/cm for gold, 10.49 g/cm for silver and 8.96 g/cm for copper. Karat
1326-430: A low coefficient of friction and fatigue resistance. It is also found in some of the lowest-melting alloys , such as Wood's metal . Cadmium is an element in some semiconductor materials. Cadmium sulfide, cadmium selenide, and cadmium telluride are used in some photodetectors and solar cells . HgCdTe detectors are sensitive to mid- infrared light and used in some motion detectors. Helium–cadmium lasers are
1404-567: A lower melting point than the transition metals in groups 3 through 11 . Cadmium and its congeners in group 12 are often not considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. The average concentration of cadmium in Earth's crust is between 0.1 and 0.5 parts per million (ppm). It was discovered in 1817 simultaneously by Stromeyer and Hermann , both in Germany, as an impurity in zinc carbonate . Cadmium occurs as
1482-615: A minor component in most zinc ores and is a byproduct of zinc production. It was used for a long time in the 1900s as a corrosion-resistant plating on steel , and cadmium compounds are used as red, orange, and yellow pigments , to color glass , and to stabilize plastic . Cadmium's use is generally decreasing because it is toxic (it is specifically listed in the European Restriction of Hazardous Substances Directive ) and nickel–cadmium batteries have been replaced with nickel–metal hydride and lithium-ion batteries. Due to it being
1560-616: A mixture of cadmium chloride and aluminium chloride , forming the Cd 2 cation, which is similar to the Hg 2 cation in mercury(I) chloride . The structures of many cadmium complexes with nucleobases , amino acids , and vitamins have been determined. Naturally occurring cadmium is composed of eight isotopes . Two of them are radioactive , and three are expected to decay but have not measurably done so under laboratory conditions. The two natural radioactive isotopes are Cd ( beta decay , half-life
1638-410: A nominal cell potential of 1.2 V . The cell consists of a positive nickel hydroxide electrode and a negative cadmium electrode plate separated by an alkaline electrolyte ( potassium hydroxide ). The European Union put a limit on cadmium in electronics in 2004 of 0.01%, with some exceptions, and in 2006 reduced the limit on cadmium content to 0.002%. Another type of battery based on cadmium
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#17328592834831716-481: A reddish color. This is why many Greek and Roman texts, and some texts from the Middle Ages, describe gold as "red". Some gold-copper- aluminium alloys form a fine surface texture at heat treatment, yielding a spangling effect. At cooling, they undergo a quasi-martensitic transformation from body-centered cubic to body-centered tetragonal phase; the transformation does not depend on the cooling rate. A polished object
1794-420: A secondary bleaching agent to attenuate the color of copper. As a result, white gold alloys can be used for many different purposes. Nickel alloys are hard and strong, and therefore good for rings and pins. Gold-palladium alloys are soft, pliable, and good for white-gold gemstone settings. The strength of gold-nickel-copper alloys is caused by formation of two phases: a gold-rich Au-Cu, and a nickel-rich Ni-Cu, and
1872-422: A significant correlation between cadmium exposure and occurrence of disease in human populations, a molecular mechanism has not yet been identified. One hypothesis holds that cadmium is an endocrine disruptor and some experimental studies have shown that it can interact with different hormonal signaling pathways. For example, cadmium can bind to the estrogen receptor alpha, and affect signal transduction along
1950-400: Is 7.7 × 10 y ) and Cd (two-neutrino double beta decay , half-life is 2.9 × 10 y ). The other three are Cd, Cd (both double electron capture ), and Cd (double beta decay); only lower limits on these half-lives have been determined. At least three isotopes – Cd, Cd, and Cd – are stable. Among the isotopes that do not occur naturally, the most long-lived are Cd with
2028-475: Is precipitated from the electrolysis solution. The British Geological Survey reports that in 2001, China was the top producer of cadmium with almost one-sixth of the world's production, closely followed by South Korea and Japan. Cadmium is a common component of electric batteries, pigments , coatings, and electroplating. In 2009, 86% of cadmium was used in batteries , predominantly in rechargeable nickel–cadmium batteries . Nickel–cadmium cells have
2106-588: Is a variant of carat . First attested in English in the mid-15th century, the word carat came from Middle French carat , in turn derived either from Italian carato or Medieval Latin carratus . These were borrowed into Medieval Europe from the Arabic qīrāṭ meaning "fruit of the carob tree", also "weight of 5 grains", ( قيراط ) and was a unit of mass though it was probably not used to measure gold in classical times. The Arabic term ultimately originates from
2184-431: Is about 0.5 eV, and neutrons below that level are deemed slow neutrons , distinct from intermediate and fast neutrons . Cadmium is created via the s-process in low- to medium-mass stars with masses of 0.6 to 10 solar masses , over thousands of years. In that process, a silver atom captures a neutron and then undergoes beta decay . Cadmium ( Latin cadmia , Greek καδμεία meaning " calamine ",
2262-443: Is associated with a higher risk of endometrial, breast, and prostate cancer as well as with osteoporosis in humans. A recent study has demonstrated that endometrial tissue is characterized by higher levels of cadmium in current and former smoking females. Cadmium exposure is associated with a large number of illnesses including kidney disease, early atherosclerosis, hypertension, and cardiovascular diseases. Although studies show
2340-457: Is believed to be the origin of the value of the karat. While there are many methods of detecting fake precious metals, there are realistically only two options available for verifying the marked fineness of metal as being reasonably accurate: assaying the metal (which requires destroying it), or using X-ray fluorescence (XRF). XRF will measure only the outermost portion of the piece of metal and so may get misled by thick plating. That becomes
2418-621: Is due to the excitation of localized surface plasmons which creates strong absorption in a broad range in plasmon resonance. The broadness of the plasmon resonance, and absorption wavelength range, depends on the interaction between different gold nanoparticles . Oxide layers can also be used to obtain blue gold from an alloy of 75% gold, 24.4% iron, and 0.6% nickel; the layer forms on heat treatment in air between 450 and 600 °C. A rich sapphire blue colored gold of 20–23K can also be obtained by alloying with ruthenium , rhodium , and three other elements and heat-treating at 1800 °C, to form
Colored gold - Misplaced Pages Continue
2496-438: Is heated in hot oil to 150–200 °C for 10 minutes then cooled below 20 °C, forming a sparkly surface covered with tiny facets. The alloy of 76% gold, 19% copper, and 5% aluminium yields a yellow color; the alloy of 76% gold, 18% copper, and 6% aluminium is pink. Green gold was known to the ancient Persians as long ago as 860 BC under the name electrum , a naturally occurring alloy of silver and gold. However, electrum
2574-456: Is increasingly being complemented or superseded by the millesimal system, described above for bullion, though jewelry generally tends to still use the karat system. Conversion between percentage of pure gold and karats: However, this system of calculation gives only the mass of pure gold contained in an alloy. The term 18-karat gold means that the alloy's mass consists of 75% of gold and 25% of other metals. The quantity of gold by volume in
2652-602: Is inhalation of fine dust and fumes, or ingestion of highly soluble cadmium compounds. Inhalation of cadmium fumes can result initially in metal fume fever , but may progress to chemical pneumonitis , pulmonary edema , and death. Cadmium is also an environmental hazard. Human exposure is primarily from fossil fuel combustion, phosphate fertilizers, natural sources, iron and steel production, cement production and related activities, nonferrous metals production, and municipal solid waste incineration. Other sources of cadmium include bread, root crops, and vegetables. There have been
2730-402: Is more brittle than other gold alloys (called the "purple plague" when it forms and causes serious faults in electronics), as it is an intermetallic compound instead of a malleable alloy, and a sharp blow may cause it to shatter. It is therefore usually machined and faceted to be used as a "gem" in conventional jewelry rather than by itself. At a lower content of gold, the material is composed of
2808-499: Is nearly always associated with sphalerite (ZnS). This association is caused by geochemical similarity between zinc and cadmium, with no geological process likely to separate them. Thus, cadmium is produced mainly as a byproduct of mining, smelting, and refining sulfidic ores of zinc, and, to a lesser degree, lead and copper . Small amounts of cadmium, about 10% of consumption, are produced from secondary sources, mainly from dust generated by recycling iron and steel scrap. Production in
2886-545: Is preferentially absorbed in the kidneys of humans. Up to about 30 mg of cadmium is commonly inhaled throughout human childhood and adolescence. Cadmium is under research for its potential toxicity to increase the risk of cancer , cardiovascular disease , and osteoporosis . The biogeochemistry of cadmium and its release to the environment is under research. Individuals and organizations have been reviewing cadmium's bioinorganic aspects for its toxicity. The most dangerous form of occupational exposure to cadmium
2964-453: Is resistant to corrosion and is used as a protective plate on other metals. As a bulk metal, cadmium is insoluble in water and is not flammable ; however, in its powdered form it may burn and release toxic fumes . Although cadmium usually has an oxidation state of +2, it also exists in the +1 state. Cadmium and its congeners are not always considered transition metals, in that they do not have partly filled d or f electron shells in
3042-666: Is the silver–cadmium battery . Cadmium electroplating , consuming 6% of the global production, is used in the aircraft industry to reduce corrosion of steel components. This coating is passivated by chromate salts. A limitation of cadmium plating is hydrogen embrittlement of high-strength steels from the electroplating process. Therefore, steel parts heat-treated to tensile strength above 1300 MPa (200 ksi) should be coated by an alternative method (such as special low-embrittlement cadmium electroplating processes or physical vapor deposition). Titanium embrittlement from cadmium-plated tool residues resulted in banishment of those tools (and
3120-434: Is the copper content: the higher the copper content, the stronger the red coloration. Pink gold uses the least copper, followed by rose gold, with red gold having the highest copper content. Examples of the common alloys for 18K rose gold, 18K red gold, 18K pink gold, and 12K red gold include: Up to 15% zinc can be added to copper-rich alloys to change their color to reddish yellow or dark yellow. 14K red gold, often found in
3198-480: Is used in the United Kingdom and United States. It is an extension of the older karat system of denoting the purity of gold by fractions of 24, such as "18 karat" for an alloy with 75% (18 parts per 24) pure gold by mass. The millesimal fineness is usually rounded to a three figure number, particularly where used as a hallmark , and the fineness may vary slightly from the traditional versions of purity. Here are
Colored gold - Misplaced Pages Continue
3276-557: Is very difficult to attain, 24-karat as a designation is permitted in commerce for a minimum of 99.95% purity), 18-karat gold is 18 parts gold, 6 parts another metal (forming an alloy with 75% gold), 12-karat gold is 12 parts gold (12 parts another metal), and so forth. In England, the carat was divisible into four grains, and the grain was divisible into four quarts. For example, a gold alloy of 127 ⁄ 128 fineness (that is, 99.2% purity) could have been described as being 23-karat, 3-grain, 1-quart gold . The karat fractional system
3354-651: The Chinese ministry of agriculture measured that 28% of rice it sampled had excess lead and 10% had excess cadmium above limits defined by law. Consumer Reports tested 28 brands of dark chocolate sold in the United States in 2022, and found cadmium in all of them, with 13 exceeding the California Maximum Allowable Dose level. Some plants such as willow trees and poplars have been found to clean both lead and cadmium from soil. Typical background concentrations of cadmium do not exceed 5 ng/m in
3432-453: The Greek kerátion ( κεράτιον ) meaning carob seed (literally "small horn") (diminutive of κέρας – kéras , "horn" ). In 309 AD, Roman Emperor Constantine I began to mint a new gold coin solidus that was 1 ⁄ 72 of a libra (Roman pound) of gold equal to a mass of 24 siliquae , where each siliqua (or carat ) was 1 ⁄ 1728 of a libra. This
3510-479: The Middle East , contains 41.67% copper. The highest karat version of rose gold, also known as crown gold , is 22 karat. Amongst the alloys made of gold, silver, and copper, the hardest is the 18.1 K pink gold (75.7% gold and 24.3% copper). An alloy with only gold and silver is the hardest at 15.5 K (64.5% gold and 35.5% silver). During ancient times, due to impurities in the smelting process, gold frequently turned
3588-411: The estrogen and MAPK signaling pathways at low doses. The tobacco plant absorbs and accumulates heavy metals such as cadmium from the surrounding soil into its leaves. Following tobacco smoke inhalation, these are readily absorbed into the body of users. Tobacco smoking is the most important single source of cadmium exposure in the general population. An estimated 10% of the cadmium content of
3666-485: The fluorite ( CaF 2 ) crystal structure, and, therefore, are brittle. Deviation from the stoichiometry results in loss of color. Slightly nonstoichiometric compositions are used, however, to achieve a fine-grained two- or three-phase microstructure with reduced brittleness. Another way of reducing brittleness is to add a small amount of palladium, copper, or silver. The intermetallic compounds tend to have poor corrosion resistance. The less noble elements are leached to
3744-404: The 1970s, the output of cadmium was 2.9 kilograms (6.5 lb) per ton of zinc. Zinc sulfide ores are roasted in the presence of oxygen , converting the zinc sulfide to the oxide . Zinc metal is produced either by smelting the oxide with carbon or by electrolysis in sulfuric acid . Cadmium is isolated from the zinc metal by vacuum distillation if the zinc is smelted, or cadmium sulfate
3822-399: The 3–6 micrometers thick colored surface oxide layer. Fineness The fineness of a precious metal object (coin, bar, jewelry, etc.) represents the weight of fine metal therein, in proportion to the total weight which includes alloying base metals and any impurities . Alloy metals are added to increase hardness and durability of coins and jewelry , alter colors, decrease
3900-699: The American Gold Eagle is embossed One Oz. Fine Gold and weighs 1.091 troy oz. Fineness of silver in Britain was traditionally expressed as the mass of silver expressed in troy ounces and pennyweights ( 1 ⁄ 20 troy ounce) in one troy pound (12 troy ounces) of the resulting alloy. Britannia silver has a fineness of 11 ounces, 10 pennyweights, or about ( 11 + 10 20 ) 12 = 95.833 % {\displaystyle {\frac {(11+{\frac {10}{20}})}{12}}=95.833\%} silver, whereas sterling silver has
3978-630: The United States began in 1907, but wide use began after World War I. Metallic cadmium can be found in the Vilyuy River basin in Siberia . Rocks mined for phosphate fertilizers contain varying amounts of cadmium, resulting in a cadmium concentration of as much as 300 mg/kg in the fertilizers and a high cadmium content in agricultural soils. Coal can contain significant amounts of cadmium, which ends up mostly in coal fly ash . Cadmium in soil can be absorbed by crops such as rice and cocoa. In 2002,
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#17328592834834056-438: The actual purity of silver articles must be no more than .004 less than the marked purity. A piece of alloy metal containing a precious metal may also have the weight of its precious component referred to as its "fine weight". For example, 1 troy ounce of 18 karat gold (which is 75% gold) may be said to have a fine weight of 0.75 troy ounces. Most modern government-issued bullion coins specify their fine weight. For example,
4134-460: The amount of reactivity. The pressurized water reactor designed by Westinghouse Electric Company uses an alloy consisting of 80% silver, 15% indium, and 5% cadmium. QLED TVs have been starting to include cadmium in construction. Some companies have been looking to reduce the environmental impact of human exposure and pollution of the material in televisions during production. Complexes based on cadmium and other heavy metals have potential for
4212-479: The atmosphere; 2 mg/kg in soil; 1 μg/L in freshwater and 50 ng/L in seawater. Concentrations of cadmium above 10 μg/L may be stable in water having low total solute concentrations and p H and can be difficult to remove by conventional water treatment processes. Cadmium is a common impurity in zinc ores, and it is most often isolated during the production of zinc . Some zinc ores concentrates from zinc sulfate ores contain up to 1.4% of cadmium. In
4290-458: The carboxylates cadmium laurate and cadmium stearate on PVC led to an increased use of those compounds in the 1970s and 1980s. The demand for cadmium in pigments, coatings, stabilizers, and alloys declined as a result of environmental and health regulations in the 1980s and 1990s; in 2006, only 7% of total cadmium consumption was used for plating, and only 10% was used for pigments. At the same time, these decreases in consumption were compensated by
4368-472: The cobalt-rich phase grains are capable of oxide-layer formation on their surface. More recently, black gold can be formed by creating nanostructures on the surface. A femtosecond laser pulse deforms the surface of the metal, creating an immensely increased surface area which absorbs virtually all the light that falls on it, thus rendering it deep black, but this method is used in high technology applications rather than for appearance in jewelry. The blackness
4446-613: The cost per weight, or avoid the cost of high-purity refinement. For example, copper is added to the precious metal silver to make a more durable alloy for use in coins, housewares and jewelry. Coin silver, which was used for making silver coins in the past, contains 90% silver and 10% copper, by mass . Sterling silver contains 92.5% silver and 7.5% of other metals, usually copper, by mass. Various ways of expressing fineness have been used and two remain in common use: millesimal fineness expressed in units of parts per 1,000 and karats or carats used only for gold . Karats measure
4524-475: The effect is slight: AuIn 2 has CIE LAB color coordinates of 79, −3.7, −4.2 which appears roughly as a grayish color. With gallium, gold forms an intermetallic AuGa 2 (58.5% Au, 14ct) which has slighter bluish hue. The melting point of AuIn 2 is 541 °C, for AuGa 2 it is 492 °C. AuIn 2 is less brittle than AuGa 2 , which itself is less brittle than AuAl 2 . A surface plating of blue gold on karat gold or sterling silver can be achieved by
4602-474: The elemental or common oxidation states. Cadmium burns in air to form brown amorphous cadmium oxide (CdO); the crystalline form of this compound is a dark red which changes color when heated, similar to zinc oxide . Hydrochloric acid , sulfuric acid , and nitric acid dissolve cadmium by forming cadmium chloride (CdCl 2 ), cadmium sulfate (CdSO 4 ), or cadmium nitrate (Cd(NO 3 ) 2 ). The oxidation state +1 can be produced by dissolving cadmium in
4680-517: The environment, and a gold-rich surface layer is formed. Direct contact of blue and purple gold elements with skin should be avoided as exposure to sweat may result in metal leaching and discoloration of the metal surface. Purple gold (also called amethyst gold and violet gold) is an alloy of gold and aluminium rich in gold–aluminium intermetallic (AuAl 2 ). Gold content in AuAl 2 is around 79% and can therefore be referred to as 18 karat gold. Purple gold
4758-524: The implementation of routine tool testing to detect cadmium contamination) in the A-12/SR-71, U-2, and subsequent aircraft programs that use titanium. Cadmium is used in the control rods of nuclear reactors, acting as a very effective neutron poison to control neutron flux in nuclear fission . When cadmium rods are inserted in the core of a nuclear reactor, cadmium absorbs neutrons, preventing them from creating additional fission events, thus controlling
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#17328592834834836-465: The industrial scale production of cadmium started in the 1930s and 1940s, the major application of cadmium was the coating of iron and steel to prevent corrosion; in 1944, 62% and in 1956, 59% of the cadmium in the United States was used for plating . In 1956, 24% of the cadmium in the United States was used for a second application in red, orange and yellow pigments from sulfides and selenides of cadmium. The stabilizing effect of cadmium chemicals like
4914-627: The intermetallic and an aluminium-rich solid solution phase. At a higher content of gold, the gold-richer intermetallic AuAl forms; the purple color is preserved to about 15% of aluminium. At 88% of gold the material is composed of AuAl and changes color. The actual composition of AuAl 2 is closer to Au 6 Al 11 as the sublattice is incompletely occupied. Blue gold is an alloy of gold and either gallium or indium . Gold-indium contains 46% gold (about 11 karat) and 54% indium, forming an intermetallic compound AuIn 2 . While several sources remark this intermetallic to have "a clear blue color", in fact
4992-406: The most common millesimal finenesses used for precious metals and the most common terms associated with them. The karat (US spelling, symbol k or Kt ) or carat (UK spelling, symbol c or Ct ) is a fractional measure of purity for gold alloys , in parts fine per 24 parts whole. The karat system is a standard adopted by US federal law. where 24-karat gold is pure (while 100% purity
5070-487: The most common. Cadmium selenide is a red pigment, commonly called cadmium red . To painters who work with the pigment, cadmium provides the most brilliant and durable yellows, oranges, and reds – so much so that during production, these colors are significantly toned down before they are ground with oils and binders or blended into watercolors , gouaches , acrylics , and other paint and pigment formulations. Because these pigments are potentially toxic, users should use
5148-596: The particle size. Colloidal solutions of those particles are used for imaging of biological tissues and solutions with a fluorescence microscope . In molecular biology, cadmium is used to block voltage-dependent calcium channels from fluxing calcium ions, as well as in hypoxia research to stimulate proteasome -dependent degradation of Hif-1α . Cadmium-selective sensors based on the fluorophore BODIPY have been developed for imaging and sensing of cadmium in cells. One powerful method for monitoring cadmium in aqueous environments involves electrochemistry . By employing
5226-447: The parts per 24, so that 18 karat = 18 ⁄ 24 = 75% and 24 karat gold is considered 100% gold. Millesimal fineness is a system of denoting the purity of platinum , gold and silver alloys by parts per thousand of pure metal by mass in the alloy. For example, an alloy containing 75% gold is denoted as "750". Many European countries use decimal hallmark stamps (i.e., "585", "750", etc.) rather than "14 k", "18 k", etc., which
5304-444: The primary decay mode is electron capture and the dominant decay product is element 47 ( silver ). Heavier isotopes decay mostly through beta emission producing element 49 ( indium ). One isotope of cadmium, Cd, absorbs neutrons with high selectivity: With very high probability, neutrons with energy below the cadmium cut-off will be absorbed; those higher than the cut-off will be transmitted . The cadmium cut-off
5382-421: The purity of white gold is given in karats. White gold's properties vary depending on the metals used and their proportions. A common white gold formulation consists of 90% wt. gold and 10% wt. nickel. Copper can be added to increase malleability. The alloys used in the jewelry industry are gold-palladium-silver and gold-nickel-copper-zinc. Palladium and nickel act as primary bleaching agents for gold; zinc acts as
5460-401: The resulting hardening of the material. The nickel used in some white gold alloys can cause an allergic reaction when worn over long periods (also notably on some wristwatch casings). This reaction, typically a minor skin rash from nickel dermatitis , occurs in about one out of eight people; because of this, many countries do not use nickel in their white gold formulations. Rose gold is
5538-436: The rice crops along the riverbanks downstream of the mines. Some members of the local agricultural communities consumed the contaminated rice and developed itai-itai disease and renal abnormalities, including proteinuria and glucosuria . The victims of this poisoning were almost exclusively post-menopausal women with low iron and low body stores of other minerals. Similar general population cadmium exposures in other parts of
5616-406: The scope of the law. The International Agency for Research on Cancer has classified cadmium and cadmium compounds as carcinogenic to humans. Although occupational exposure to cadmium is linked to lung and prostate cancer, there is still uncertainty about the carcinogenicity of cadmium in low environmental exposure. Recent data from epidemiological studies suggest that intake of cadmium through diet
5694-408: The treatment of cancer, but their use is often limited due to toxic side effects. Cadmium oxide was used in black and white television phosphors and in the blue and green phosphors of color television cathode ray tubes. Cadmium sulfide (CdS) is used as a photoconductive surface coating for photocopier drums. Various cadmium salts are used in paint pigments, with CdS as a yellow pigment being
5772-587: The world have not resulted in the same health problems because the populations maintained sufficient iron and other mineral levels. Thus, although cadmium is a major factor in the itai-itai disease in Japan, most researchers have concluded that it was one of several factors. Cadmium is one of ten substances banned by the European Union's Restriction of Hazardous Substances (RoHS) directive, which regulates hazardous substances in electrical and electronic equipment, but allows for certain exemptions and exclusions from
5850-552: The yellow precipitate with hydrogen sulfide . Additionally Stromeyer discovered that one supplier sold zinc carbonate instead of zinc oxide. Stromeyer found the new element as an impurity in zinc carbonate (calamine), and, for 100 years, Germany remained the only important producer of the metal. The metal was named after the Latin word for calamine, because it was found in this zinc ore. Stromeyer noted that some impure samples of calamine changed color when heated but pure calamine did not. He
5928-476: Was persistent in studying these results and eventually isolated cadmium metal by roasting and reducing the sulfide . The potential for cadmium yellow as pigment was recognized in the 1840s, but the lack of cadmium limited this application. Even though cadmium and its compounds are toxic in certain forms and concentrations, the British Pharmaceutical Codex from 1907 states that cadmium iodide
6006-509: Was used as a medication to treat "enlarged joints, scrofulous glands, and chilblains". In 1907, the International Astronomical Union defined the international ångström in terms of a red cadmium spectral line (1 wavelength = 6438.46963 Å). This was adopted by the 7th General Conference on Weights and Measures in 1927. In 1960, the definitions of both the metre and ångström were changed to use krypton . After
6084-516: Was used even thousands of years before that, by both the Akkadians and Ancient Egyptians (as evidenced by the Royal Cemetery at Ur ). Even the tops of some Egyptian pyramids were known to be capped in thin layers of electrum. It actually appears as greenish-yellow rather than green. Fired enamels adhere better to these alloys than to pure gold. Cadmium can also be added to gold alloys to create
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