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21,700 | OCS will continue to be the ground control system of record until the new segment, Next Generation GPS Operation Control System (OCX), is fully developed and functional. The new capabilities provided by OCX will be the cornerstone for revolutionizing GPS's mission capabilities, enabling U.S. Space Force to greatly enha... | https://en.wikipedia.org/wiki?curid=11866 |
21,701 | The GPS OCX program represents a critical part of GPS modernization and provides significant information assurance improvements over the current GPS OCS program. | https://en.wikipedia.org/wiki?curid=11866 |
21,702 | On September 14, 2011, the U.S. Air Force announced the completion of GPS OCX Preliminary Design Review and confirmed that the OCX program is ready for the next phase of development. | https://en.wikipedia.org/wiki?curid=11866 |
21,703 | The GPS OCX program has missed major milestones and is pushing its launch into 2021, 5 years past the original deadline. According to the Government Accounting Office, even this new deadline looks shaky. | https://en.wikipedia.org/wiki?curid=11866 |
21,704 | The user segment (US) is composed of hundreds of thousands of U.S. and allied military users of the secure GPS Precise Positioning Service, and tens of millions of civil, commercial and scientific users of the Standard Positioning Service. In general, GPS receivers are composed of an antenna, tuned to the frequencies t... | https://en.wikipedia.org/wiki?curid=11866 |
21,705 | GPS receivers may include an input for differential corrections, using the RTCM SC-104 format. This is typically in the form of an RS-232 port at 4,800 bit/s speed. Data is actually sent at a much lower rate, which limits the accuracy of the signal sent using RTCM. Receivers with internal DGPS receivers can outperform ... | https://en.wikipedia.org/wiki?curid=11866 |
21,706 | Many GPS receivers can relay position data to a PC or other device using the NMEA 0183 protocol. Although this protocol is officially defined by the National Marine Electronics Association (NMEA), references to this protocol have been compiled from public records, allowing open source tools like gpsd to read the protoc... | https://en.wikipedia.org/wiki?curid=11866 |
21,707 | While originally a military project, GPS is considered a dual-use technology, meaning it has significant civilian applications as well. | https://en.wikipedia.org/wiki?curid=11866 |
21,708 | GPS has become a widely deployed and useful tool for commerce, scientific uses, tracking, and surveillance. GPS's accurate time facilitates everyday activities such as banking, mobile phone operations, and even the control of power grids by allowing well synchronized hand-off switching. | https://en.wikipedia.org/wiki?curid=11866 |
21,709 | Many civilian applications use one or more of GPS's three basic components: absolute location, relative movement, and time transfer. | https://en.wikipedia.org/wiki?curid=11866 |
21,710 | The U.S. government controls the export of some civilian receivers. All GPS receivers capable of functioning above above sea level and , or designed or modified for use with unmanned missiles and aircraft, are classified as munitions (weapons)—which means they require State Department export licenses. This rule applies... | https://en.wikipedia.org/wiki?curid=11866 |
21,711 | Disabling operation above these limits exempts the receiver from classification as a munition. Vendor interpretations differ. The rule refers to operation at both the target altitude and speed, but some receivers stop operating even when stationary. This has caused problems with some amateur radio balloon launches that... | https://en.wikipedia.org/wiki?curid=11866 |
21,712 | These limits only apply to units or components exported from the United States. A growing trade in various components exists, including GPS units from other countries. These are expressly sold as ITAR-free. | https://en.wikipedia.org/wiki?curid=11866 |
21,713 | GPS type navigation was first used in war in the 1991 Persian Gulf War, before GPS was fully developed in 1995, to assist Coalition Forces to navigate and perform maneuvers in the war. The war also demonstrated the vulnerability of GPS to being jammed, when Iraqi forces installed jamming devices on likely targets that ... | https://en.wikipedia.org/wiki?curid=11866 |
21,714 | GPS's vulnerability to jamming is a threat that continues to grow as jamming equipment and experience grows. GPS signals have been reported to have been jammed many times over the years for military purposes. Russia seems to have several objectives for this behavior, such as intimidating neighbors while undermining con... | https://en.wikipedia.org/wiki?curid=11866 |
21,715 | The GPS implements two major corrections to its time signals for relativistic effects: one for relative velocity of satellite and receiver, using the special theory of relativity, and one for the difference in gravitational potential between satellite and receiver, using general relativity. The acceleration of the sate... | https://en.wikipedia.org/wiki?curid=11866 |
21,716 | While most clocks derive their time from Coordinated Universal Time (UTC), the atomic clocks on the satellites are set to "GPS time". The difference is that GPS time is not corrected to match the rotation of the Earth, so it does not contain leap seconds or other corrections that are periodically added to UTC. GPS time... | https://en.wikipedia.org/wiki?curid=11866 |
21,717 | The GPS navigation message includes the difference between GPS time and UTC. GPS time is 18 seconds ahead of UTC because of the leap second added to UTC on December 31, 2016. Receivers subtract this offset from GPS time to calculate UTC and specific time zone values. New GPS units may not show the correct UTC time unti... | https://en.wikipedia.org/wiki?curid=11866 |
21,718 | GPS time is theoretically accurate to about 14 nanoseconds, due to the clock drift relative to International Atomic Time that the atomic clocks in GPS transmitters experience Most receivers lose some accuracy in their interpretation of the signals and are only accurate to about 100 nanoseconds. | https://en.wikipedia.org/wiki?curid=11866 |
21,719 | As opposed to the year, month, and day format of the Gregorian calendar, the GPS date is expressed as a week number and a seconds-into-week number. The week number is transmitted as a ten-bit field in the C/A and P(Y) navigation messages, and so it becomes zero again every 1,024 weeks (19.6 years). GPS week zero starte... | https://en.wikipedia.org/wiki?curid=11866 |
21,720 | The navigational signals transmitted by GPS satellites encode a variety of information including satellite positions, the state of the internal clocks, and the health of the network. These signals are transmitted on two separate carrier frequencies that are common to all satellites in the network. Two different encodin... | https://en.wikipedia.org/wiki?curid=11866 |
21,721 | Each GPS satellite continuously broadcasts a "navigation message" on L1 (C/A and P/Y) and L2 (P/Y) frequencies at a rate of 50 bits per second (see bitrate). Each complete message takes 750 seconds ( minutes) to complete. The message structure has a basic format of a 1500-bit-long frame made up of five subframes, each ... | https://en.wikipedia.org/wiki?curid=11866 |
21,722 | The first subframe of each frame encodes the week number and the time within the week, as well as the data about the health of the satellite. The second and the third subframes contain the "ephemeris" – the precise orbit for the satellite. The fourth and fifth subframes contain the "almanac", which contains coarse orbi... | https://en.wikipedia.org/wiki?curid=11866 |
21,723 | All satellites broadcast at the same frequencies, encoding signals using unique code-division multiple access (CDMA) so receivers can distinguish individual satellites from each other. The system uses two distinct CDMA encoding types: the coarse/acquisition (C/A) code, which is accessible by the general public, and the... | https://en.wikipedia.org/wiki?curid=11866 |
21,724 | The ephemeris is updated every 2 hours and is sufficiently stable for 4 hours, with provisions for updates every 6 hours or longer in non-nominal conditions. The almanac is updated typically every 24 hours. Additionally, data for a few weeks following is uploaded in case of transmission updates that delay data upload. | https://en.wikipedia.org/wiki?curid=11866 |
21,725 | All satellites broadcast at the same two frequencies, 1.57542 GHz (L1 signal) and 1.2276 GHz (L2 signal). The satellite network uses a CDMA spread-spectrum technique where the low-bitrate message data is encoded with a high-rate pseudo-random (PRN) sequence that is different for each satellite. The receiver must be awa... | https://en.wikipedia.org/wiki?curid=11866 |
21,726 | The L3 signal at a frequency of 1.38105 GHz is used to transmit data from the satellites to ground stations. This data is used by the United States Nuclear Detonation (NUDET) Detection System (USNDS) to detect, locate, and report nuclear detonations (NUDETs) in the Earth's atmosphere and near space. One usage is the en... | https://en.wikipedia.org/wiki?curid=11866 |
21,727 | The L5 frequency band at 1.17645 GHz was added in the process of GPS modernization. This frequency falls into an internationally protected range for aeronautical navigation, promising little or no interference under all circumstances. The first Block IIF satellite that provides this signal was launched in May 2010. On ... | https://en.wikipedia.org/wiki?curid=11866 |
21,728 | In 2011, a conditional waiver was granted to LightSquared to operate a terrestrial broadband service near the L1 band. Although LightSquared had applied for a license to operate in the 1525 to 1559 band as early as 2003 and it was put out for public comment, the FCC asked LightSquared to form a study group with the GPS... | https://en.wikipedia.org/wiki?curid=11866 |
21,729 | Because all of the satellite signals are modulated onto the same L1 carrier frequency, the signals must be separated after demodulation. This is done by assigning each satellite a unique binary sequence known as a Gold code. The signals are decoded after demodulation using addition of the Gold codes corresponding to th... | https://en.wikipedia.org/wiki?curid=11866 |
21,730 | If the almanac information has previously been acquired, the receiver picks the satellites to listen for by their PRNs, unique numbers in the range 1 through 32. If the almanac information is not in memory, the receiver enters a search mode until a lock is obtained on one of the satellites. To obtain a lock, it is nece... | https://en.wikipedia.org/wiki?curid=11866 |
21,731 | Processing of the navigation message enables the determination of the time of transmission and the satellite position at this time. For more information see Demodulation and Decoding, Advanced. | https://en.wikipedia.org/wiki?curid=11866 |
21,732 | The receiver uses messages received from satellites to determine the satellite positions and time sent. The "x, y," and "z" components of satellite position and the time sent ("s") are designated as ["x, y, z, s"] where the subscript "i" denotes the satellite and has the value 1, 2, ..., "n", where "n" ≥ 4. When the ti... | https://en.wikipedia.org/wiki?curid=11866 |
21,733 | where "d" is the geometric distance or range between receiver and satellite "i" (the values without subscripts are the "x, y," and "z" components of receiver position): | https://en.wikipedia.org/wiki?curid=11866 |
21,734 | Since the equations have four unknowns ["x, y, z, b"]—the three components of GPS receiver position and the clock bias—signals from at least four satellites are necessary to attempt solving these equations. They can be solved by algebraic or numerical methods. Existence and uniqueness of GPS solutions are discussed by ... | https://en.wikipedia.org/wiki?curid=11866 |
21,735 | The amount of error in the results varies with the received satellites' locations in the sky, since certain configurations (when the received satellites are close together in the sky) cause larger errors. Receivers usually calculate a running estimate of the error in the calculated position. This is done by multiplying... | https://en.wikipedia.org/wiki?curid=11866 |
21,736 | The GPS equations can be solved by numerical and analytical methods. Geometrical interpretations can enhance the understanding of these solution methods. | https://en.wikipedia.org/wiki?curid=11866 |
21,737 | The measured ranges, called pseudoranges, contain clock errors. In a simplified idealization in which the ranges are synchronized, these true ranges represent the radii of spheres, each centered on one of the transmitting satellites. The solution for the position of the receiver is then at the intersection of the surfa... | https://en.wikipedia.org/wiki?curid=11866 |
21,738 | In practice, there are many sources of inaccuracy besides clock bias, including random errors as well as the potential for precision loss from subtracting numbers close to each other if the centers of the spheres are relatively close together. This means that the position calculated from three satellites alone is unlik... | https://en.wikipedia.org/wiki?curid=11866 |
21,739 | If the pseudorange between the receiver and satellite "i" and the pseudorange between the receiver and satellite "j" are subtracted, , the common receiver clock bias ("b") cancels out, resulting in a difference of distances . The locus of points having a constant difference in distance to two points (here, two satellit... | https://en.wikipedia.org/wiki?curid=11866 |
21,740 | The receiver position can be interpreted as the center of an inscribed sphere (insphere) of radius "bc", given by the receiver clock bias "b" (scaled by the speed of light "c"). The insphere location is such that it touches other spheres. The circumscribing spheres are centered at the GPS satellites, whose radii equal ... | https://en.wikipedia.org/wiki?curid=11866 |
21,741 | The clock in the receiver is usually not of the same quality as the ones in the satellites and will not be accurately synchronized to them. This produces pseudoranges with large differences compared to the true distances to the satellites. Therefore, in practice, the time difference between the receiver clock and the s... | https://en.wikipedia.org/wiki?curid=11866 |
21,742 | When more than four satellites are available, the calculation can use the four best, or more than four simultaneously (up to all visible satellites), depending on the number of receiver channels, processing capability, and geometric dilution of precision (GDOP). | https://en.wikipedia.org/wiki?curid=11866 |
21,743 | Using more than four involves an over-determined system of equations with no unique solution; such a system can be solved by a least-squares or weighted least squares method. | https://en.wikipedia.org/wiki?curid=11866 |
21,744 | Both the equations for four satellites, or the least squares equations for more than four, are non-linear and need special solution methods. A common approach is by iteration on a linearized form of the equations, such as the Gauss–Newton algorithm. | https://en.wikipedia.org/wiki?curid=11866 |
21,745 | The GPS was initially developed assuming use of a numerical least-squares solution method—i.e., before closed-form solutions were found. | https://en.wikipedia.org/wiki?curid=11866 |
21,746 | One closed-form solution to the above set of equations was developed by S. Bancroft. Its properties are well known; in particular, proponents claim it is superior in low-GDOP situations, compared to iterative least squares methods. | https://en.wikipedia.org/wiki?curid=11866 |
21,747 | Bancroft's method is algebraic, as opposed to numerical, and can be used for four or more satellites. When four satellites are used, the key steps are inversion of a 4x4 matrix and solution of a single-variable quadratic equation. Bancroft's method provides one or two solutions for the unknown quantities. When there ar... | https://en.wikipedia.org/wiki?curid=11866 |
21,748 | When a receiver uses more than four satellites for a solution, Bancroft uses the generalized inverse (i.e., the pseudoinverse) to find a solution. A case has been made that iterative methods, such as the Gauss–Newton algorithm approach for solving over-determined non-linear least squares problems, generally provide mor... | https://en.wikipedia.org/wiki?curid=11866 |
21,749 | Leick et al. (2015) states that "Bancroft's (1985) solution is a very early, if not the first, closed-form solution." | https://en.wikipedia.org/wiki?curid=11866 |
21,750 | Other closed-form solutions were published afterwards, although their adoption in practice is unclear. | https://en.wikipedia.org/wiki?curid=11866 |
21,751 | GPS error analysis examines error sources in GPS results and the expected size of those errors. GPS makes corrections for receiver clock errors and other effects, but some residual errors remain uncorrected. Error sources include signal arrival time measurements, numerical calculations, atmospheric effects (ionospheric... | https://en.wikipedia.org/wiki?curid=11866 |
21,752 | In the United States, GPS receivers are regulated under the Federal Communications Commission's (FCC) Part 15 rules. As indicated in the manuals of GPS-enabled devices sold in the United States, as a Part 15 device, it "must accept any interference received, including interference that may cause undesired operation." W... | https://en.wikipedia.org/wiki?curid=11866 |
21,753 | The spectrum allocated for GPS L1 use by the FCC is 1559 to 1610 MHz, while the spectrum allocated for satellite-to-ground use owned by Lightsquared is the Mobile Satellite Service band. Since 1996, the FCC has authorized licensed use of the spectrum neighboring the GPS band of 1525 to 1559 MHz to the Virginia company ... | https://en.wikipedia.org/wiki?curid=11866 |
21,754 | In January 2011, the FCC conditionally authorized LightSquared's wholesale customers—such as Best Buy, Sharp, and C Spire—to only purchase an integrated satellite-ground-based service from LightSquared and re-sell that integrated service on devices that are equipped to only use the ground-based signal using LightSquare... | https://en.wikipedia.org/wiki?curid=11866 |
21,755 | GPS receiver manufacturers design GPS receivers to use spectrum beyond the GPS-allocated band. In some cases, GPS receivers are designed to use up to 400 MHz of spectrum in either direction of the L1 frequency of 1575.42 MHz, because mobile satellite services in those regions are broadcasting from space to ground, and ... | https://en.wikipedia.org/wiki?curid=11866 |
21,756 | The FCC adopted rules in February 2003 that allowed Mobile Satellite Service (MSS) licensees such as LightSquared to construct a small number of ancillary ground-based towers in their licensed spectrum to "promote more efficient use of terrestrial wireless spectrum." In those 2003 rules, the FCC stated "As a preliminar... | https://en.wikipedia.org/wiki?curid=11866 |
21,757 | The FCC and LightSquared have each made public commitments to solve the GPS interference issue before the network is allowed to operate. According to Chris Dancy of the Aircraft Owners and Pilots Association, airline pilots with the type of systems that would be affected "may go off course and not even realize it." The... | https://en.wikipedia.org/wiki?curid=11866 |
21,758 | On February 14, 2012, the FCC moved to bar LightSquared's planned national broadband network after being informed by the National Telecommunications and Information Administration (NTIA), the federal agency that coordinates spectrum uses for the military and other federal government entities, that "there is no practica... | https://en.wikipedia.org/wiki?curid=11866 |
21,759 | Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver and was formerly named hydrargyrum ( ) from the Greek words, "hydor" (water) and "argyros" (silver). A heavy, silvery d-block element, mercury is the only metallic element that is known to be liquid at standard condit... | https://en.wikipedia.org/wiki?curid=18617142 |
21,760 | Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is obtained by grinding natural cinnabar or synthetic mercuric sulfide. | https://en.wikipedia.org/wiki?curid=18617142 |
21,761 | Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, mercury switches, mercury relays, fluorescent lamps and other devices, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favor ... | https://en.wikipedia.org/wiki?curid=18617142 |
21,762 | Mercury remains in use in scientific research applications and in amalgam for dental restoration in some locales. It is also used in fluorescent lighting. Electricity passed through mercury vapor in a fluorescent lamp produces short-wave ultraviolet light, which then causes the phosphor in the tube to fluoresce, making... | https://en.wikipedia.org/wiki?curid=18617142 |
21,763 | Mercury poisoning can result from exposure to water-soluble forms of mercury (such as mercuric chloride or methylmercury), by inhalation of mercury vapor, or by ingesting any form of mercury. | https://en.wikipedia.org/wiki?curid=18617142 |
21,764 | Mercury is a heavy, silvery-white metal that is liquid at room temperature. Compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity. | https://en.wikipedia.org/wiki?curid=18617142 |
21,765 | It has a freezing point of −38.83 °C and a boiling point of 356.73 °C, both the lowest of any stable metal, although preliminary experiments on copernicium and flerovium have indicated that they have even lower boiling points. This effect is due to lanthanide contraction and relativistic contraction reducing the radius... | https://en.wikipedia.org/wiki?curid=18617142 |
21,766 | Mercury does not react with most acids, such as dilute sulfuric acid, although oxidizing acids such as concentrated sulfuric acid and nitric acid or aqua regia dissolve it to give sulfate, nitrate, and chloride. Like silver, mercury reacts with atmospheric hydrogen sulfide. Mercury reacts with solid sulfur flakes, whic... | https://en.wikipedia.org/wiki?curid=18617142 |
21,767 | Mercury dissolves many metals such as gold and silver to form amalgams. Iron is an exception, and iron flasks have traditionally been used to trade mercury. Several other first row transition metals with the exception of manganese, copper and zinc are also resistant in forming amalgams. Other elements that do not readi... | https://en.wikipedia.org/wiki?curid=18617142 |
21,768 | Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact. Since the amalgam destroys the aluminium oxide layer which protects metallic aluminium from oxidizing in-depth (as in iron rusting), even small amounts of mercury can seriously corrode aluminium. For ... | https://en.wikipedia.org/wiki?curid=18617142 |
21,769 | There are seven stable isotopes of mercury, with being the most abundant (29.86%). The longest-lived radioisotopes are with a half-life of 444 years, and with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives that are less than a day. and are the most often studied NMR-active nuclei, havin... | https://en.wikipedia.org/wiki?curid=18617142 |
21,770 | "Hg" is the modern chemical symbol for mercury. It is an abbreviation of , a romanized form of the ancient Greek name for mercury, (). is a Greek compound word meaning "water-silver", from - (-), the root of () "water", and () "silver". Like the English name quicksilver ("living-silver"), this name was due to mercury's... | https://en.wikipedia.org/wiki?curid=18617142 |
21,771 | The modern English name "mercury" comes from the planet Mercury. In medieval alchemy, the seven known metals—quicksilver, gold, silver, copper, iron, lead, and tin—were associated with the seven planets. Quicksilver was associated with the fastest planet, which had been named after the Roman god Mercury, who was associ... | https://en.wikipedia.org/wiki?curid=18617142 |
21,772 | In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health, although it is now known that exposure to mercury vapor leads to serious adverse health effects. The first emperor of a unified China, Qín Shǐ Huáng Dì—allegedly buried in a tomb that contained rivers of flo... | https://en.wikipedia.org/wiki?curid=18617142 |
21,773 | In November 2014 "large quantities" of mercury were discovered in a chamber 60 feet below the 1800-year-old pyramid known as the "Temple of the Feathered Serpent," "the third largest pyramid of Teotihuacan," Mexico along with "jade statues, jaguar remains, a box filled with carved shells and rubber balls". | https://en.wikipedia.org/wiki?curid=18617142 |
21,774 | Aristotle recounts that Daedalus made a wooden statue of Venus move by pouring quicksilver in its interior. In Greek mythology Daedalus gave the appearance of voice in his statues using quicksilver. The ancient Greeks used cinnabar (mercury sulfide) in ointments; the ancient Egyptians and the Romans used it in cosmetic... | https://en.wikipedia.org/wiki?curid=18617142 |
21,775 | Alchemists thought of mercury as the First Matter from which all metals were formed. They believed that different metals could be produced by varying the quality and quantity of sulfur contained within the mercury. The purest of these was gold, and mercury was called for in attempts at the transmutation of base (or imp... | https://en.wikipedia.org/wiki?curid=18617142 |
21,776 | The mines in Almadén (Spain), Monte Amiata (Italy), and Idrija (now Slovenia) dominated mercury production from the opening of the mine in Almadén 2500 years ago, until new deposits were found at the end of the 19th century. | https://en.wikipedia.org/wiki?curid=18617142 |
21,777 | Mercury is an extremely rare element in Earth's crust, having an average crustal abundance by mass of only 0.08 parts per million (ppm). Because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be extraordinarily concentrated considering the element'... | https://en.wikipedia.org/wiki?curid=18617142 |
21,778 | Beginning in 1558, with the invention of the patio process to extract silver from ore using mercury, mercury became an essential resource in the economy of Spain and its American colonies. Mercury was used to extract silver from the lucrative mines in New Spain and Peru. Initially, the Spanish Crown's mines in Almadén ... | https://en.wikipedia.org/wiki?curid=18617142 |
21,779 | Former mines in Italy, the United States and Mexico, which once produced a large proportion of the world supply, have now been completely mined out or, in the case of Slovenia (Idrija) and Spain (Almadén), shut down due to the fall of the price of mercury. Nevada's McDermitt Mine, the last mercury mine in the United St... | https://en.wikipedia.org/wiki?curid=18617142 |
21,780 | Mercury is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction is | https://en.wikipedia.org/wiki?curid=18617142 |
21,781 | In 2005, China was the top producer of mercury with almost two-thirds global share followed by Kyrgyzstan. Several other countries are believed to have unrecorded production of mercury from copper electrowinning processes and by recovery from effluents. | https://en.wikipedia.org/wiki?curid=18617142 |
21,782 | Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic causes of mercury poisoning. In China, prison labor was used by a private mining company as recently as the 1950s to develop new cinnabar mines. Thousands of prisoners were used by the Luo Xi mining ... | https://en.wikipedia.org/wiki?curid=18617142 |
21,783 | A newspaper claimed that an unidentified European Union directive calling for energy-efficient lightbulbs to be made mandatory by 2012 encouraged China to re-open cinnabar mines to obtain the mercury required for CFL bulb manufacture. Environmental dangers have been a concern, particularly in the southern cities of Fos... | https://en.wikipedia.org/wiki?curid=18617142 |
21,784 | Abandoned mercury mine processing sites often contain very hazardous waste piles of roasted cinnabar calcines. Water run-off from such sites is a recognized source of ecological damage. Former mercury mines may be suited for constructive re-use. For example, in 1976 Santa Clara County, California purchased the historic... | https://en.wikipedia.org/wiki?curid=18617142 |
21,785 | All known mercury compounds exhibit one of two positive oxidation states: I and II. Experiments have failed to unequivocally demonstrate any higher oxidation states: both the claimed 1976 electrosynthesis of an unstable Hg(III) species and 2007 cryogenic isolation of HgF have disputed interpretations and remain difficu... | https://en.wikipedia.org/wiki?curid=18617142 |
21,786 | Unlike its lighter neighbors, cadmium and zinc, mercury usually forms simple stable compounds with metal-metal bonds. Most mercury(I) compounds are diamagnetic and feature the dimeric cation, Hg. Stable derivatives include the chloride and nitrate. Treatment of Hg(I) compounds complexation with strong ligands such as s... | https://en.wikipedia.org/wiki?curid=18617142 |
21,787 | Indicative of its tendency to bond to itself, mercury forms mercury polycations, which consist of linear chains of mercury centers, capped with a positive charge. One example is . | https://en.wikipedia.org/wiki?curid=18617142 |
21,788 | Mercury(II) is the most common oxidation state and is the main one in nature as well. All four mercuric halides are known. They form tetrahedral complexes with other ligands but the halides adopt linear coordination geometry, somewhat like Ag does. Best known is mercury(II) chloride, an easily sublimating white solid. ... | https://en.wikipedia.org/wiki?curid=18617142 |
21,789 | Mercury(II) oxide, the main oxide of mercury, arises when the metal is exposed to air for long periods at elevated temperatures. It reverts to the elements upon heating near 400 °C, as was demonstrated by Joseph Priestley in an early synthesis of pure oxygen. Hydroxides of mercury are poorly characterized, as they are ... | https://en.wikipedia.org/wiki?curid=18617142 |
21,790 | Being a soft metal, mercury forms very stable derivatives with the heavier chalcogens. Preeminent is mercury(II) sulfide, HgS, which occurs in nature as the ore cinnabar and is the brilliant pigment vermillion. Like ZnS, HgS crystallizes in two forms, the reddish cubic form and the black zinc blende form. The latter so... | https://en.wikipedia.org/wiki?curid=18617142 |
21,791 | Mercury(II) salts form a variety of complex derivatives with ammonia. These include Millon's base (HgN), the one-dimensional polymer (salts of )), and "fusible white precipitate" or [Hg(NH)]Cl. Known as Nessler's reagent, potassium tetraiodomercurate(II) () is still occasionally used to test for ammonia owing to its te... | https://en.wikipedia.org/wiki?curid=18617142 |
21,792 | Organic mercury compounds are historically important but are of little industrial value in the western world. Mercury(II) salts are a rare example of simple metal complexes that react directly with aromatic rings. Organomercury compounds are always divalent and usually two-coordinate and linear geometry. Unlike organoc... | https://en.wikipedia.org/wiki?curid=18617142 |
21,793 | Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some liquid-in-glass thermometers, especially those used to measure high temperatures. A still increasing amount is used as gaseous mercury in fluorescent lamps, while most of the other app... | https://en.wikipedia.org/wiki?curid=18617142 |
21,794 | Mercury and its compounds have been used in medicine, although they are much less common today than they once were, now that the toxic effects of mercury and its compounds are more widely understood. An example of the early therapeutic application of mercury of was published in 1787 by James Lind. | https://en.wikipedia.org/wiki?curid=18617142 |
21,795 | Mercury is an ingredient in dental amalgams. Thiomersal (called "Thimerosal" in the United States) is an organic compound used as a preservative in vaccines, though this use is in decline. Thiomersal is metabolized to ethyl mercury. Although it was widely speculated that this mercury-based preservative could cause or t... | https://en.wikipedia.org/wiki?curid=18617142 |
21,796 | Another mercury compound, merbromin (Mercurochrome), is a topical antiseptic used for minor cuts and scrapes that is still in use in some countries. | https://en.wikipedia.org/wiki?curid=18617142 |
21,797 | Mercury in the form of one of its common ores, cinnabar, is used in various traditional medicines, especially in traditional Chinese medicine. Review of its safety has found that cinnabar can lead to significant mercury intoxication when heated, consumed in overdose, or taken long term, and can have adverse effects at ... | https://en.wikipedia.org/wiki?curid=18617142 |
21,798 | Today, the use of mercury in medicine has greatly declined in all respects, especially in developed countries. Thermometers and sphygmomanometers containing mercury were invented in the early 18th and late 19th centuries, respectively. In the early 21st century, their use is declining and has been banned in some countr... | https://en.wikipedia.org/wiki?curid=18617142 |
21,799 | Chlorine is produced from sodium chloride (common salt, NaCl) using electrolysis to separate the metallic sodium from the chlorine gas. Usually the salt is dissolved in water to produce a brine. By-products of any such chloralkali process are hydrogen (H) and sodium hydroxide (NaOH), which is commonly called caustic so... | https://en.wikipedia.org/wiki?curid=18617142 |
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