Neon is a chemical element with symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, inert monatomic gas under standard conditions, with about two-thirds the density of air, it was discovered in 1898 as one of the three residual rare inert elements remaining in dry air, after nitrogen, oxygen and carbon dioxide were removed. Neon was the second of these three rare gases to be discovered and was recognized as a new element from its bright red emission spectrum; the name neon is derived from the Greek νέον, neuter singular form of νέος, meaning new. Neon is chemically inert, no uncharged neon compounds are known; the compounds of neon known include ionic molecules, molecules held together by van der Waals forces and clathrates. During cosmic nucleogenesis of the elements, large amounts of neon are built up from the alpha-capture fusion process in stars. Although neon is a common element in the universe and solar system, it is rare on Earth, it composes about 18.2 ppm of air by a smaller fraction in Earth's crust.
The reason for neon's relative scarcity on Earth and the inner planets is that neon is volatile and forms no compounds to fix it to solids. As a result, it escaped from the planetesimals under the warmth of the newly ignited Sun in the early Solar System; the outer atmosphere of Jupiter is somewhat depleted of neon, although for a different reason. It is lighter than air, causing it to escape from Earth's atmosphere. Neon gives a distinct reddish-orange glow when used in low-voltage neon glow lamps, high-voltage discharge tubes and neon advertising signs; the red emission line from neon causes the well known red light of helium–neon lasers. Neon has few other commercial uses, it is commercially extracted by the fractional distillation of liquid air. Since air is the only source, it is more expensive than helium. Neon was discovered in 1898 by the British chemists Sir William Ramsay and Morris W. Travers in London. Neon was discovered when Ramsay chilled a sample of air until it became a liquid warmed the liquid and captured the gases as they boiled off.
The gases nitrogen and argon had been identified, but the remaining gases were isolated in their order of abundance, in a six-week period beginning at the end of May 1898. First to be identified was krypton; the next, after krypton had been removed, was a gas which gave a brilliant red light under spectroscopic discharge. This gas, identified in June, was named "neon", the Greek analogue of the Latin novum suggested by Ramsay's son; the characteristic brilliant red-orange color emitted by gaseous neon when excited electrically was noted immediately. Travers wrote: "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget."A second gas was reported along with neon, having the same density as argon but with a different spectrum – Ramsay and Travers named it metargon. However, subsequent spectroscopic analysis revealed it to be argon contaminated with carbon monoxide; the same team discovered xenon by the same process, in September 1898. Neon's scarcity precluded its prompt application for lighting along the lines of Moore tubes, which used nitrogen and which were commercialized in the early 1900s.
After 1902, Georges Claude's company Air Liquide produced industrial quantities of neon as a byproduct of his air-liquefaction business. In December 1910 Claude demonstrated modern neon lighting based on a sealed tube of neon. Claude tried to sell neon tubes for indoor domestic lighting, due to their intensity, but the market failed because homeowners objected to the color. In 1912, Claude's associate began selling neon discharge tubes as eye-catching advertising signs and was more successful. Neon tubes were introduced to the U. S. in 1923 with two large neon signs bought by a Los Angeles Packard car dealership. The glow and arresting red color made neon advertising different from the competition; the intense color and vibrancy of neon equated with American society at the time, suggesting a "century of progress" and transforming cities into sensational new environments filled with radiating advertisements and "electro-graphic architecture". Neon played a role in the basic understanding of the nature of atoms in 1913, when J. J. Thomson, as part of his exploration into the composition of canal rays, channeled streams of neon ions through a magnetic and an electric field and measured the deflection of the streams with a photographic plate.
Thomson observed two separate patches of light on the photographic plate, which suggested two different parabolas of deflection. Thomson concluded that some of the atoms in the neon gas were of higher mass than the rest. Though not understood at the time by Thomson, this was the first discovery of isotopes of stable atoms. Thomson's device was a crude version of the instrument. Neon is the second lightest inert gas. Neon has three stable isotopes: 21Ne and 22Ne. 21Ne and 22Ne are primordial and nucleogenic and their variations in natural abundance are well understood. In contrast, 20Ne is not known to be radiogenic; the causes of the variation of 20Ne in the Earth have thus been hotly debated. The princ
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, therefore lower energy, than the absorbed radiation; the most striking example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum, thus invisible to the human eye, while the emitted light is in the visible region, which gives the fluorescent substance a distinct color that can be seen only when exposed to UV light. Fluorescent materials cease to glow nearly when the radiation source stops, unlike phosphorescent materials, which continue to emit light for some time after. Fluorescence has many practical applications, including mineralogy, medicine, chemical sensors, fluorescent labelling, biological detectors, cosmic-ray detection, most fluorescent lamps. Fluorescence occurs in nature in some minerals and in various biological states in many branches of the animal kingdom.
An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and in 1565 by Nicolás Monardes in the infusion known as lignum nephriticum. It was derived from the wood of Pterocarpus indicus and Eysenhardtia polystachya; the chemical compound responsible for this fluorescence is matlaline, the oxidation product of one of the flavonoids found in this wood. In 1819, Edward D. Clarke and in 1822 René Just Haüy described fluorescence in fluorites, Sir David Brewster described the phenomenon for chlorophyll in 1833 and Sir John Herschel did the same for quinine in 1845. In his 1852 paper on the "Refrangibility" of light, George Gabriel Stokes described the ability of fluorspar and uranium glass to change invisible light beyond the violet end of the visible spectrum into blue light, he named this phenomenon fluorescence: "I am inclined to coin a word, call the appearance fluorescence, from fluor-spar, as the analogous term opalescence is derived from the name of a mineral." The name was derived from the mineral fluorite, some examples of which contain traces of divalent europium, which serves as the fluorescent activator to emit blue light.
In a key experiment he used a prism to isolate ultraviolet radiation from sunlight and observed blue light emitted by an ethanol solution of quinine exposed by it. Fluorescence occurs when an orbital electron of a molecule, atom, or nanostructure, relaxes to its ground state by emitting a photon from an excited singlet state: Excitation: S 0 + h ν e x → S 1 Fluorescence: S 1 → S 0 + h ν e m + h e a t Here h ν is a generic term for photon energy with h = Planck's constant and ν = frequency of light; the specific frequencies of exciting and emitted lights are depended on the particular system. S0 is called the ground state of the fluorophore, S1 is its first excited singlet state. A molecule in S1 can relax by various competing pathways, it can undergo non-radiative relaxation in which the excitation energy is dissipated as heat to the solvent. Excited organic molecules can relax via conversion to a triplet state, which may subsequently relax via phosphorescence, or by a secondary non-radiative relaxation step.
Relaxation from S1 can occur through interaction with a second molecule through fluorescence quenching. Molecular oxygen is an efficient quencher of fluorescence just because of its unusual triplet ground state. In most cases, the emitted light has a longer wavelength, therefore lower energy, than the absorbed radiation. However, when the absorbed electromagnetic radiation is intense, it is possible for one electron to absorb two photons; the emitted radiation may be of the same wavelength as the absorbed radiation, termed "resonance fluorescence". Molecules that are excited through light absorption or via a different process can transfer energy to a second'sensitized' molecule, converted to its excited state and can fluoresce; the fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed. Φ = Number of photons emitted Number of photons absorbed The maximum possible fluorescence quantum yield is 1.0.
Compounds with quantum yields of 0.10 are still considered quite fluorescent. Another way to define the quantum yield of fluorescence is by the rate of excited state decay: Φ = k f ∑ i k i where k f is the rate constant of spontaneous emission of radiation and ∑ i k i is the sum of all rates of
Sir Humphry Davy, 1st Baronet was a Cornish chemist and inventor, best remembered today for isolating, using electricity, a series of elements for the first time: potassium and sodium in 1807 and calcium, barium and boron the following year, as well as discovering the elemental nature of chlorine and iodine. He studied the forces involved in these separations, inventing the new field of electrochemistry. In 1799 Davy experimented with nitrous oxide and was astonished at how it made him laugh, so he nicknamed it "laughing gas", wrote about its potential anaesthetic properties in relieving pain during surgery. Berzelius called Davy's 1806 Bakerian Lecture On Some Chemical Agencies of Electricity "one of the best memoirs which has enriched the theory of chemistry." Davy was a baronet, President of the Royal Society, Member of the Royal Irish Academy, Fellow of the Geological Society. He invented the Davy lamp and a early form of arc lamp, he joked. Davy was born in Penzance, Cornwall in England on 17 December, 1778.
Davy's brother, writes that the society of their hometown was characterised by "an unbounded credulity respecting the supernatural and monstrous... Amongst the middle and higher classes, there was little taste for literature, still less for science... Hunting, wrestling, cockfighting ending in drunkenness, were what they most delighted in". At the age of six, Davy was sent to the grammar school at Penzance. Three years his family moved to Varfell, near Ludgvan, subsequently, in term-time Davy boarded with John Tonkin, his godfather and his guardian. On leaving Penzance grammar school in 1793, Tonkin paid for Davy to attend Truro Grammar School in 1793 to finish his education under the Rev Dr Cardew, who, in a letter to Davies Gilbert, said dryly: "I could not discern the faculties by which he was afterwards so much distinguished." Yet, Davy entertained his school friends with writing poetry and telling stories from One Thousand and One Nights. Reflecting on his school days, in a letter to his mother, Davy wrote: "Learning is a true pleasure.
Davy said: "I consider it fortunate I was left much to myself as a child, put upon no particular plan of study... What I am I made myself." Davy's brother praises his "native vigour": "there belonged, however, to his mind, it cannot be doubted, the genuine quality of genius, or of that power of intellect which exalts its possessor above the crowd."After Davy's father died in 1794, Tonkin apprenticed him to John Bingham Borlase, a surgeon with a practice in Penzance. Davy's indenture is dated 10 February 1795. In the apothecary's dispensary, Davy became a chemist, conducted his earliest chemical experiments in a garret in Tonkin's house. Davy's friends said: "This boy Humphry is incorrigible, he will blow us all into the air." His elder sister complained of the ravages made on her dresses by corrosive substances. Davy was taught French by a refugee priest, in 1797 read Lavoisier's Traité élémentaire de chimie: much of his future work can be seen as reacting against Lavoisier's work and the dominance of French chemists.
As a poet, over one hundred and sixty manuscript poems were written by Davy, the majority of which are found in his personal notebooks. Most of his written poems were not published, he chose instead to share a few of them with his friends. Eight of his known poems were published, his poems reflected his views on both his career and his pereception of certain aspects of human life. He wrote on human endeavours and aspects of life like death, geology, natural theology and chemistry. John Ayrton Paris remarked that poetry written by the young Davy "bear the stamp of lofty genius". Davy's first preserved poem entitled The Sons of Genius is dated 1795 and marked by the usual immaturity of youth. Other poems written in the following years On the Mount's Bay and St Michael's Mount, are descriptive verses, showing sensibility but no true poetic imagination. Three of Davy's paintings from around 1796 have been donated to the Penlee House museum at Penzance. One is of the view from above Gulval showing the church, Mount's Bay and the Mount, while the other two depict Loch Lomond in Scotland.
While writing verses at the age of 17 in honour of his first love, he was eagerly discussing the question of the materiality of heat with his Quaker friend and mentor Robert Dunkin. Dunkin remarked:'I tell thee what, thou art the most quibbling hand at a dispute I met with in my life.' One winter day he took Davy to the Larigan River, To show him that rubbing two plates of ice together developed sufficient energy by motion, to melt them, that after the motion was suspended, the pieces were united by regelation. It was a crude form of analogous experiment exhibited by Davy in the lecture-room of the Royal Institution that elicited considerable attention; as professor at the Royal Institution, Davy repeated many of the ingenious experiments he learned from his friend and mentor, Robert Dunkin. Though he started writing his poems, albeit haphazardly, as a reflection of his views on his career and on life most of his final poems concentrated on immortality and death; this was after he started experiencing failing a decline both in health and career.
Davies Giddy met Davy in Penzance carelessly swinging on the half-gate of Dr Borlase's house, interested by his talk invited him to his house at Tredrea and offered him the use of his library. This led to an introduction to Dr Edwards. Edwards was a lecturer in
An LED lamp or LED light bulb is an electric light for use in light fixtures that produces light using one or more light-emitting diodes. LED lamps have a lifespan many times longer than equivalent incandescent lamps, are more efficient than most fluorescent lamps, with some LED chips able to emit up to 303 lumens per watt. However, LED lamps require an electronic LED driver circuit when operated from mains power lines, losses from this circuit mean the efficiency of the lamp is lower than the efficiency of the LED chips it uses; the most efficient commercially available LED lamps have efficiencies of 200 lumens per watt. Commercially available LED chips have efficiencies of over 220 Lm/W; the LED lamp market is projected to grow by more than twelve-fold over the next decade, from $2 billion in the beginning of 2014 to $25 billion in 2023, a compound annual growth rate of 25%. As of 2016, LEDs use only about 10% of the energy an incandescent lamp requires. Similar to incandescent lamps, LEDs come to full brightness with no warm-up delay.
Frequent switching on and off does not reduce life expectancy as with fluorescent lighting. Light output decreases over the lifetime of the LED; some LED lamps are made to be a directly compatible drop-in replacement for incandescent or fluorescent lamps. LED lamp packaging may show the light outpur in lumens, the power consumption in watts, the color temperature in Kelvin or a colour description such as "warm white", "cool white" or "daylight", the operating temperature range, sometimes the equivalent wattage of an incandescent lamp delivering the same output in lumens; the directional emission characteristics of LEDs affect the design of lamps. While a single power LED may produce as much light output as an incandescent lamp using several times as much power, in most general lighting applications multiple LEDs are used; this can form a lamp with improved cost, light distribution, heat dissipation and also color-rendering characteristics. LEDs run on direct current, whereas mains current is alternating current and at much higher voltage than the LED can accept.
LED lamps can contain a circuit for converting the mains AC into DC at the correct voltage. These circuits contain rectifiers and may have other active electronic components, which may permit the lamp to be dimmed. In an LED filament lamp, the driving circuit is simplified because many LED junctions in series have the same operating voltage as the AC supply. Before the introduction of LED lamps, three types of lamps were used for the bulk of general lighting: Incandescent lights, which produce light with a glowing filament heated by electric current; these are inefficient, having a luminous efficacy of 10-17 lumens/W, have a short lifetime of 1000 hours. They are being phased out of general lighting applications. Incandescent lamps produce a continuous black body spectrum of light similar to sunlight, so produce high Color rendering index. Fluorescent lamps, which produce ultraviolet light by a glow discharge between two electrodes in a low pressure tube of mercury vapor, converted to visible light by a fluorescent coating on the inside of the tube.
These are more efficient than incandescent lights, having a luminous efficacy of around 60 lumens/W, have a longer lifetime 6,000-15,000 hours, are used for residential and office lighting. However, their mercury content makes them a hazard to the environment, they have to be disposed of as hazardous waste. Metal-halide lamps, which produce light by an arc between two electrodes in an atmosphere of argon and other metals, iodine or bromine; these were the most efficient white electric lights before LEDs, having a luminous efficacy of 75–100 lumens/W and have a long bulb lifetime of 6,000-15,000 hours, but because they require a 5 - 7 minute warmup period before turning on, are not used for residential lighting, but for commercial and industrial wide area lighting, outdoor security lights and streetlights. Like fluorescents, they contain hazardous mercury. Considered as electric energy converters, all these existing lamps are inefficient, emitting more of their input energy as waste heat than as visible light.
Global electric lighting in 1997 consumed 2016 terawatthours of energy. Lighting consumes 12% of electrical energy produced by industrialized countries; the increasing scarcity of energy resources, the environmental costs of producing energy the discovery of global warming due to carbon dioxide emitted by the burning of fossil fuels, which are the largest source of energy for electric power generation, created an increased incentive to develop more energy-efficient electric lights. The first low-powered LEDs were developed in the early 1960s, only produced light in the low, red frequencies of the spectrum; the first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation in 1994. The existence of blue LEDs and high-efficiency LEDs led to the development of the first'white LED', which employed a phosphor coating to convert the emitted blue light to red and green frequencies creating a light that appears white. Isamu Akasaki, Hiroshi Amano and Nakamura were awarded the 2014 Nobel Prize in Physics for the invention of the blue LED.
China further boosted LED research and development in 1995 and demonstrated its first LED Christmas tree in 1998. The new LED technology application became prevalent at the start of the 21st century by US and Japan and starting 2004 by Korea and China (S
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, each transition has a specific energy difference; this collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore, spectroscopy can be used to identify the elements in matter of unknown composition; the emission spectra of molecules can be used in chemical analysis of substances. In physics, emission is the process by which a higher energy quantum mechanical state of a particle becomes converted to a lower one through the emission of a photon, resulting in the production of light; the frequency of light emitted is a function of the energy of the transition.
Since energy must be conserved, the energy difference between the two states equals the energy carried off by the photon. The energy states of the transitions can lead to emissions over a large range of frequencies. For example, visible light is emitted by the coupling of electronic states in molecules. On the other hand, nuclear shell transitions can emit high energy gamma rays, while nuclear spin transitions emit low energy radio waves; the emittance of an object quantifies. This may be related to other properties of the object through the Stefan–Boltzmann law. For most substances, the amount of emission varies with the temperature and the spectroscopic composition of the object, leading to the appearance of color temperature and emission lines. Precise measurements at many wavelengths allow the identification of a substance via emission spectroscopy. Emission of radiation is described using semi-classical quantum mechanics: the particle's energy levels and spacings are determined from quantum mechanics, light is treated as an oscillating electric field that can drive a transition if it is in resonance with the system's natural frequency.
The quantum mechanics problem is treated using time-dependent perturbation theory and leads to the general result known as Fermi's golden rule. The description has been superseded by quantum electrodynamics, although the semi-classical version continues to be more useful in most practical computations; when the electrons in the atom are excited, for example by being heated, the additional energy pushes the electrons to higher energy orbitals. When the electrons fall back down and leave the excited state, energy is re-emitted in the form of a photon; the wavelength of the photon is determined by the difference in energy between the two states. These emitted photons form the element's spectrum; the fact that only certain colors appear in an element's atomic emission spectrum means that only certain frequencies of light are emitted. Each of these frequencies are related to energy by the formula: E photon = h ν,where E photon is the energy of the photon, ν is its frequency, h is Planck's constant.
This concludes. The principle of the atomic emission spectrum explains the varied colors in neon signs, as well as chemical flame test results; the frequencies of light that an atom can emit are dependent on states. When excited, an electron moves to orbital; when the electron falls back to its ground level the light is emitted. The above picture shows the visible light emission spectrum for hydrogen. If only a single atom of hydrogen were present only a single wavelength would be observed at a given instant. Several of the possible emissions are observed because the sample contains many hydrogen atoms that are in different initial energy states and reach different final energy states; these different combinations lead to simultaneous emissions at different wavelengths. As well as the electronic transitions discussed above, the energy of a molecule can change via rotational and vibronic transitions; these energy transitions lead to spaced groups of many different spectral lines, known as spectral bands.
Unresolved band spectra may appear as a spectral continuum. Light consists of electromagnetic radiation of different wavelengths. Therefore, when the elements or their compounds are heated either on a flame or by an electric arc they emit energy in the form of light. Analysis of this light, with the help of a spectroscope gives us a discontinuous spectrum. A spectroscope or a spectrometer is an instrument, used for separating the components of light, which have different wavelengths; the spectrum appears in a series of lines called the line spectrum. This line spectrum is called an atomic spectrum; each element has a different atomic spectrum. The production of line spectra by the atoms of an element indicate that an atom can radiate only a certain amount of energy; this leads to the conclusion that bound electrons cannot have just any amount of energy but only a certain amount of energy. The emission spectrum can be used to determine the composition of a material, since it is different for each element of the periodic table.
One example is astronomical spectroscopy: iden
Mercury is a chemical element with symbol Hg and atomic number 80. It is known as quicksilver and was named hydrargyrum. A heavy, silvery d-block element, mercury is the only metallic element, liquid at standard conditions for temperature and pressure. Mercury occurs in deposits throughout the world as cinnabar; the red pigment vermilion is obtained by synthetic mercuric sulfide. Mercury is used in thermometers, 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 phased out in clinical environments in favor of alternatives such as alcohol- or galinstan-filled glass thermometers and thermistor- or infrared-based electronic instruments. Mechanical pressure gauges and electronic strain gauge sensors have replaced mercury sphygmomanometers. Mercury remains in use in scientific research applications and in amalgam for dental restoration in some locales.
It is used in fluorescent lighting. Electricity passed through mercury vapor in a fluorescent lamp produces short-wave ultraviolet light, which causes the phosphor in the tube to fluoresce, making visible light. Mercury poisoning can result from exposure to water-soluble forms of mercury, by inhalation of mercury vapor, or by ingesting any form of mercury. Mercury is a silvery-white liquid metal. Compared to other metals, it is a fair conductor of electricity, 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 lower boiling points. Upon freezing, the volume of mercury decreases by 3.59% and its density changes from 13.69 g/cm3 when liquid to 14.184 g/cm3 when solid. The coefficient of volume expansion is 181.59 × 10−6 at 0 °C, 181.71 × 10−6 at 20 °C and 182.50 × 10−6 at 100 °C. Solid mercury can be cut with a knife. A complete explanation of mercury's extreme volatility delves deep into the realm of quantum physics, but it can be summarized as follows: mercury has a unique electron configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d, 6s subshells.
Because this configuration resists removal of an electron, mercury behaves to noble gases, which form weak bonds and hence melt at low temperatures. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus; the absence of a filled inner f shell is the reason for the somewhat higher melting temperature of cadmium and zinc, although both these metals still melt and, in addition, have unusually low boiling points. 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 and chloride. Like silver, mercury reacts with atmospheric hydrogen sulfide. Mercury reacts with solid sulfur flakes. Mercury dissolves many metals such as silver to form amalgams. Iron is an exception, iron flasks have traditionally been used to trade mercury.
Several other first row transition metals with the exception of manganese and zinc are resistant in forming amalgams. Other elements that do not form amalgams with mercury include platinum. Sodium amalgam is a common reducing agent in organic synthesis, is used in high-pressure sodium lamps. Mercury 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 small amounts of mercury can corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft. Mercury embrittlement is the most common type of liquid metal embrittlement. There are seven stable isotopes of mercury, with 202Hg being the most abundant; the longest-lived radioisotopes are 194Hg with a half-life of 444 years, 203Hg with a half-life of 46.612 days. Most of the remaining radioisotopes have half-lives.
199Hg and 201Hg are the most studied NMR-active nuclei, having spins of 1⁄2 and 3⁄2 respectively. Hg is the modern chemical symbol for mercury, it comes from hydrargyrum, a Latinized form of the Greek word ὑδράργυρος, a compound word meaning "water-silver" – since it is liquid like water and shiny like silver. The element was named after the Roman god Mercury, known for his mobility, it is associated with the planet Mercury. Mercury is the only metal for which the al
Orange is the colour between yellow and red on the spectrum of visible light. Human eyes perceive orange when observing light with a dominant wavelength between 585 and 620 nanometres. In painting and traditional colour theory, it is a secondary colour of pigments, created by mixing yellow and red, it is named after the fruit of the same name. The orange colour of carrots, sweet potatoes and many other fruits and vegetables comes from carotenes, a type of photosynthetic pigment; these pigments convert the light energy that the plants absorb from the sun into chemical energy for the plants' growth. The hues of autumn leaves are from the same pigment after chlorophyll is removed. In Europe and America, surveys show that orange is the colour most associated with amusement, the unconventional, warmth, energy, danger and aroma, the autumn and Allhallowtide seasons, as well as having long been the national colour of the Netherlands and the House of Orange, it serves as the political colour of Christian democracy political ideology and most Christian democratic political parties.
In Asia it is an important symbolic colour of Hinduism. The colour orange is named after the appearance of the ripe orange fruit; the word comes from the Old French orange, from the old term for the fruit, pomme d'orange. The French word, in turn, comes from the Italian arancia, based on Arabic nāranj, derived from the Sanskrit naranga; the first recorded use of orange as a colour name in English was in 1512, in a will now filed with the Public Record Office. Prior to this word being introduced to the English-speaking world, saffron existed in the English language. Crog referred to the saffron colour, so that orange was referred to as ġeolurēad for reddish orange, or ġeolucrog for yellowish orange. Alternatively, orange things were sometimes described as red such as red deer, red hair, the Red Planet and robin redbreast. In ancient Egypt, artists used an orange mineral pigment called realgar for tomb paintings, as well as other uses, it was used by Medieval artists for the colouring of manuscripts.
Pigments were made in ancient times from a mineral known as orpiment. Orpiment was an important item of trade in the Roman Empire and was used as a medicine in China although it contains arsenic and is toxic, it was used as a fly poison and to poison arrows. Because of its yellow-orange colour, it was a favourite with alchemists searching for a way to make gold, in both China and the West. Before the late 15th century, the colour orange without the name. Portuguese merchants brought the first orange trees to Europe from Asia in the late 15th and early 16th century, along with the Sanskrit naranga, which became part of several European languages: "naranja" in Spanish, "laranja" in Portuguese, "orange" in English; the House of Orange-Nassau was one of the most influential royal houses in Europe in the 16th and 17th centuries. It originated in 1163 the tiny Principality of Orange, a feudal state of 108 square miles north of Avignon in southern France; the Principality of Orange took its name not from the fruit, but from a Roman-Celtic settlement on the site, founded in 36 or 35 BC and was named Arausio, after a Celtic water god.
The family of the Prince of Orange adopted the name and the colour orange in the 1570s. The colour came to be associated with Protestantism, due to participation by the House of Orange on the Protestant side in the French Wars of Religion. One member of the house, William I of Orange, organised the Dutch resistance against Spain, a war that lasted for eighty years, until the Netherlands won its independence; the House's arguably most prominent member, William III of Orange, became King of England in 1689, after the downfall of the Catholic James II. Due to William III, orange became an important political colour in Europe. William was a Protestant, as such he defended the Protestant minority of Ireland against the majority Roman Catholic population; as a result, the Protestants of Ireland were known as Orangemen. Orange became one of the colours of the Irish flag, symbolising the Protestant heritage, his rebel flag became the forerunner of The Netherland's modern flag. When the Dutch settlers of South Africa rebelled against the British in the late 19th century, they organised what they called the Orange Free State.
In the United States, the flag of the City of New York has an orange stripe, to remember the Dutch colonists who founded the city. William of Orange is remembered as the founder of the College of William & Mary, Nassau County in New York is named after the House of Orange-Nassau. In the 18th century orange was sometimes used to depict the robes of Pomona, the goddess of fruitful abundance. Oranges themselves became more common in northern Europe, thanks to the 17th century invention of the heated greenhouse, a building type which became known as an orangerie; the French artist Jean-Honoré Fragonard depicted an allegorical figure of "inspiration" dressed in orange. In 1797 a French scientist Louis Vauquelin discovered the mineral crocoite, or lead chromate, which led in 1809 to the invention of the synthetic pigment chrome orange. Other synthetic pigments, cobalt red, cobalt yellow, cobalt orange, the last made from cadmium sulfide plus cadmium selenide, soon followed; these new pigments, plus the invention of the