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100-596: Cerulean ( / s ə ˈ r uː l i ə n / ), also spelled caerulean , is a variety of the hue of blue that may range from a light azure blue to a more intense sky blue, and may be mixed as well with the hue of green. The first recorded use of cerulean as a colour name in English was in 1590. The word is derived from the Latin word caeruleus , "dark blue, blue, or blue-green", which in turn probably derives from caerulum , diminutive of caelum , "heaven, sky". "Cerulean blue"
200-417: A dominant wavelength between approximately 450 and 495 nanometres. Blues with a higher frequency and thus a shorter wavelength gradually look more violet, while those with a lower frequency and a longer wavelength gradually appear more green. Purer blues are in the middle of this range, e.g., around 470 nanometres. Isaac Newton included blue as one of the seven colours in his first description of
300-494: A sequestering agent for certain toxic heavy metals . Pharmaceutical-grade Prussian blue in particular is used for people who have ingested thallium ( Tl ) or radioactive caesium ( Cs , Cs ). According to the International Atomic Energy Agency (IAEA), an adult male can eat at least 10 g of Prussian blue per day without serious harm. The U.S. Food and Drug Administration (FDA) has determined
400-507: A French chemist, Louis Jacques Thénard , made a synthetic cobalt blue pigment which became immensely popular with painters. In 1824 the Societé pour l'Encouragement d'Industrie in France offered a prize for the invention of an artificial ultramarine which could rival the natural colour made from lapis lazuli. The prize was won in 1826 by a chemist named Jean Baptiste Guimet, but he refused to reveal
500-574: A common colour for military uniforms and later, in the late 20th century, for business suits. Because blue has commonly been associated with harmony, it was chosen as the colour of the flags of the United Nations and the European Union . In the United States and Europe, blue is the colour that both men and women are most likely to choose as their favourite, with at least one recent survey showing
600-474: A deep blue colour, was once employed in medieval years, but it is unstable pigment, losing its colour especially under dry conditions. Lapis lazuli , mined in Afghanistan for more than three thousand years, was used for jewelry and ornaments, and later was crushed and powdered and used as a pigment. The more it was ground, the lighter the blue colour became. Natural ultramarine , made by grinding lapis lazuli into
700-678: A fine powder, was the finest available blue pigment in the Middle Ages and the Renaissance . It was extremely expensive, and in Italian Renaissance art, it was often reserved for the robes of the Virgin Mary . Intense efforts have focused on blue flowers and the possibility that natural blue colourants could be used as food dyes. Commonly, blue colours in plants are anthocyanins : "the largest group of water-soluble pigments found widespread in
800-459: A more complete list see the List of colours ). In nature, many blue phenomena arise from structural colouration , the result of interference between reflections from two or more surfaces of thin films , combined with refraction as light enters and exits such films. The geometry then determines that at certain angles, the light reflected from both surfaces interferes constructively, while at other angles,
900-468: A quick-drying binding agent, such as egg yolk ( tempera painting ); or with a slow-drying oil, such as linseed oil , for oil painting . Two inorganic but synthetic blue pigments are cerulean blue (primarily cobalt(II) stanate: Co 2 SnO 4 ) and Prussian blue (milori blue: primarily Fe 7 (CN) 18 ). The chromophore in blue glass and glazes is cobalt (II). Diverse cobalt(II) salts such as cobalt carbonate or cobalt(II) aluminate are mixed with
1000-472: A time onto paper. This method could produce almost all the colours in the spectrum with reasonable accuracy. On the HSV colour wheel , the complement of blue is yellow ; that is, a colour corresponding to an equal mixture of red and green light. On a colour wheel based on traditional colour theory ( RYB ) where blue was considered a primary colour, its complementary colour is considered to be orange (based on
1100-612: A wide gamut of colours. Red and blue mixed together form violet, blue and yellow together form green. Mixing all three primary colours together produces a dark brown. From the Renaissance onward, painters used this system to create their colours (see RYB colour model ). The RYB model was used for colour printing by Jacob Christoph Le Blon as early as 1725. Later, printers discovered that more accurate colours could be created by using combinations of cyan, magenta, yellow, and black ink, put onto separate inked plates and then overlaid one at
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#17328589570911200-479: A word for the colour blue. Colour names often developed individually in natural languages, typically beginning with black and white (or dark and light), and then adding red , and only much later – usually as the last main category of colour accepted in a language – adding the colour blue, probably when blue pigments could be manufactured reliably in the culture using that language. The term blue generally describes colours perceived by humans observing light with
1300-425: Is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula Fe 3+ 4 [Fe ( CN ) 6 ] 3 . Turnbull's blue is chemically identical, but is made from different reagents , and its slightly different color stems from different impurities and particle sizes. Prussian blue was created in the early 18th century and is the first modern synthetic pigment. It
1400-458: Is absorbed, and the reflected light appears blue as a result. Like most high- chroma pigments , Prussian blue cannot be accurately displayed on a computer display. Prussian blue is electrochromic —changing from blue to colorless upon reduction . This change is caused by reduction of the Fe(III) to Fe(II), eliminating the intervalence charge transfer that causes Prussian blue's color. Because it
1500-496: Is believed to have been accidentally created when Diesbach used potash tainted with blood to create some red cochineal dye. The original dye required potash, ferric sulfate , and dried cochineal. Instead, the blood, potash, and iron sulfate reacted to create a compound known as iron ferrocyanide, which, unlike the desired red pigment, has a very distinct blue hue. It was named Preußisch blau and Berlinisch Blau in 1709 by its first trader. The pigment readily replaced
1600-408: Is called Blausäure ('blue acid'). Cyanide also acquired its name from this relationship. Prussian blue pigment is significant since it was the first stable and relatively lightfast blue pigment to be widely used since the loss of knowledge regarding the synthesis of Egyptian blue . European painters had previously used a number of pigments such as indigo dye , smalt , and Tyrian purple , and
1700-470: Is closely related to the Prussian blue, but it significantly differs by its crystallographic structure, molecular framework pore size, and its color. The cubic sodium Prussian white, Na (2−x) K x Fe 2 (CN) 6 ·yH 2 O , and potassium Prussian white, K (2−x) Na x Fe 2 (CN) 6 ·yH 2 O , are candidates as cathode materials for Na-ion batteries . The insertion of Na and K cations in
1800-469: Is displayed the colour cerulean frost . Cerulean frost is one of the colours in the special set of metallic coloured Crayola crayons called Silver Swirls , the colours of which were formulated by Crayola in 1990. Curious Blue is one of the brighter-toned colours of cerulean. Blue Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in
1900-413: Is easily made, cheap, nontoxic, and intensely colored, Prussian blue has attracted many applications. It was adopted as a pigment very soon after its invention and was almost immediately widely used in oil paints, watercolor, and dyeing. The dominant uses are for pigments: about 12,000 tonnes of Prussian blue are produced annually for use in black and bluish inks . A variety of other pigments also contain
2000-459: Is identified by Rex Art and some other manufacturers as "cobalt turquoise". Cerulean is inert with good light resistance, and it exhibits a high degree of stability in both watercolour and acrylic . Cobalt stannate pigment was first synthesized in 1789 by the Swiss chemist Albrecht Höpfner by heating roasted cobalt and tin oxides together. Subsequently, there was limited German production under
2100-412: Is notoriously variable due to the presence of lattice defects, allowing it to be hydrated to various degrees as water molecules are incorporated into the structure to occupy cation vacancies. The variability of Prussian blue's composition is attributable to its low solubility , which leads to its rapid precipitation without the time to achieve full equilibrium between solid and liquid. Prussian blue
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#17328589570912200-399: Is now the blue of blue jeans. As the pace of organic chemistry accelerated, a succession of synthetic blue dyes were discovered including Indanthrone blue , which had even greater resistance to fading during washing or in the sun, and copper phthalocyanine . Woad and true indigo were once used but since the early 1900s, all indigo is synthetic. Produced on an industrial scale, indigo
2300-453: Is prepared as a very fine colloidal dispersion , because the compound is not soluble in water. It contains variable amounts of other ions and its appearance depends sensitively on the size of the colloidal particles. The pigment is used in paints , it became prominent in 19th-century aizuri-e ( 藍摺り絵 ) Japanese woodblock prints , and it is the traditional "blue" in technical blueprints . In medicine, orally administered Prussian blue
2400-683: Is reduced to ferrocyanide by the phenols. The ferric chloride and ferrocyanide react to form Prussian blue. Comparing the absorbance at 700 nm of the samples to the standards allows for the determination of total phenols or polyphenols . Prussian blue is present in some preparations of laundry bluing , such as Mrs. Stewart's Bluing . Prussian blue (PB) has been studied for its applications in electrochemical energy storage since 1978. Prussian Blue proper (the Fe-Fe solid) shows two well-defined reversible redox transitions in K solutions. Weakly solvated potassium ions (as well as Rb and Cs , not shown) have
2500-518: Is still used. Some sources claim that cerulean blue was first marketed in the United Kingdom by colourman George Rowney , as "coeruleum" in the early 1860s. However, the British firm of Roberson was buying "Blue No. 58 (Cerulium)" from a German firm of Frauenknecht and Stotz prior to Rowney. Cerulean blue was only available as a watercolour in the 1860s and was not widely adopted until the 1870s when it
2600-494: Is strongly colored and tends towards black and dark blue when mixed into oil paints . The exact hue depends on the method of preparation, which dictates the particle size. The intense blue color of Prussian blue is associated with the energy of the transfer of electrons from Fe(II) to Fe(III). Many such mixed-valence compounds absorb certain wavelengths of visible light resulting from intervalence charge transfer . In this case, orange-red light around 680 nanometers in wavelength
2700-447: Is the sodium end-member of the totally reduced form of the Prussian blue in which all iron is present as Fe(II). It is a sodium hexacyanoferrate of Fe(II) of formula Na 2 Fe[Fe(CN) 6 ] . Its molecular weight value is 314 g/mol . A more generic formula allowing for the substitution of Na cations by K cations is A (2−x) B x Fe 2 (CN) 6 (in which A or B = Na or K ). The Prussian white
2800-555: Is the blue chromophore in stained glass windows , such as those in Gothic cathedrals and in Chinese porcelain beginning in the Tang dynasty . Copper(II) (Cu ) also produces many blue compounds, including the commercial algicide copper(II) sulfate (CuSO 4 5H 2 O). Similarly, vanadyl salts and solutions are often blue, e.g. vanadyl sulfate . When sunlight passes through the atmosphere,
2900-646: Is the blue of blue jeans. Blue dyes are organic compounds, both synthetic and natural. For food, the triarylmethane dye Brilliant blue FCF is used for candies. The search continues for stable, natural blue dyes suitable for the food industry. Various raspberry -flavoured foods are dyed blue. This was done to distinguish strawberry , watermelon and raspberry -flavoured foods. The company ICEE used Blue No. 1 for their blue raspberry ICEEs. Blue pigments were once produced from minerals, especially lapis lazuli and its close relative ultramarine . These minerals were crushed, ground into powder, and then mixed with
3000-686: Is the colour of light between violet and cyan on the visible spectrum . Hues of blue include indigo and ultramarine , closer to violet; pure blue, without any mixture of other colours; Azure, which is a lighter shade of blue, similar to the colour of the sky; Cyan, which is midway in the spectrum between blue and green , and the other blue-greens such as turquoise , teal , and aquamarine . Blue also varies in shade or tint; darker shades of blue contain black or grey, while lighter tints contain white. Darker shades of blue include ultramarine, cobalt blue , navy blue , and Prussian blue ; while lighter tints include sky blue , azure , and Egyptian blue (for
3100-432: Is the name of a blue-green pigment consisting of cobalt stannate ( Co 2 SnO 4 ). The pigment was first synthesized in the late eighteenth century by Albrecht Höpfner, a Swiss chemist, and it was known as Höpfner blue during the first half of the nineteenth century. Art suppliers began referring to cobalt stannate as cerulean in the second half of the nineteenth century. It was not widely used by artists until
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3200-545: Is the oldest known painting where Prussian blue was used. Around 1710, painters at the Prussian court were already using the pigment. At around the same time, Prussian blue arrived in Paris, where Antoine Watteau and later his successors Nicolas Lancret and Jean-Baptiste Pater used it in their paintings. François Boucher used the pigment extensively for both blues and greens. In 1731, Georg Ernst Stahl published an account of
3300-566: Is used as an antidote for certain kinds of heavy metal poisoning , e.g., by thallium(I) and radioactive isotopes of cesium . The therapy exploits Prussian blue's ion-exchange properties and high affinity for certain " soft " metal cations . It is on the World Health Organization's List of Essential Medicines , the most important medications needed in a basic health system . Prussian blue lent its name to prussic acid (hydrogen cyanide) derived from it. In German, hydrogen cyanide
3400-597: The Baltic Sea area and Northern Europe , and are also found in Eastern , Central , and Southern Europe . Blue eyes are also found in parts of Western Asia , most notably in Afghanistan , Syria , Iraq , and Iran . In Estonia , 99% of people have blue eyes. In Denmark in 1978, only 8% of the population had brown eyes, though through immigration, today that number is about 11%. In Germany , about 75% have blue eyes. In
3500-562: The Caucasus , and as far away as Mauritania . It was used in the funeral mask of Tutankhamun (1341–1323 BC). A term for Blue was relatively rare in many forms of ancient art and decoration, and even in ancient literature. The Ancient Greek poets described the sea as green, brown or "the colour of wine". The colour is mentioned several times in the Hebrew Bible as ' tekhelet '. Reds, blacks, browns, and ochres are found in cave paintings from
3600-560: The Immaculate Conception in diocese currently or formerly under the Spanish Crown . Pantone , in a press release, declared the pale hue of cerulean at right, which they call cerulean , as the "colour of the millennium". The source of this colour is the " Pantone Textile Paper eXtended (TPX)" colour list, colour #15-4020 TPX—Cerulean. This bright tone of cerulean is the colour called cerulean by Crayola crayons . At right
3700-465: The Munsell colour wheel ). In 1993, high-brightness blue LEDs were demonstrated by Shuji Nakamura of Nichia Corporation . In parallel, Isamu Akasaki and Hiroshi Amano of Nagoya University were working on a new development which revolutionized LED lighting. Nakamura was awarded the 2006 Millennium Technology Prize for his invention. Nakamura, Hiroshi Amano and Isamu Akasaki were awarded
3800-822: The Nobel Prize in Physics in 2014 for the invention of an efficient blue LED. Lasers emitting in the blue region of the spectrum became widely available to the public in 2010 with the release of inexpensive high-powered 445–447 nm laser diode technology. Previously the blue wavelengths were accessible only through DPSS which are comparatively expensive and inefficient, but still widely used by scientists for applications including optogenetics , Raman spectroscopy , and particle image velocimetry , due to their superior beam quality. Blue gas lasers are also still commonly used for holography , DNA sequencing , optical pumping , among other scientific and medical applications. Blue
3900-629: The Old French bleu , a word of Germanic origin, related to the Old High German word blao (meaning 'shimmering, lustrous'). In heraldry , the word azure is used for blue . In Russian , Spanish, Mongolian , Irish , and some other languages, there is no single word for blue, but rather different words for light blue ( голубой , goluboj ; Celeste ) and dark blue ( синий , sinij ; Azul ) (see Colour term ). Several languages, including Japanese and Lakota Sioux , use
4000-474: The RGB (additive) colour model . It lies between violet and cyan on the spectrum of visible light . The term blue generally describes colours perceived by humans observing light with a dominant wavelength that's between approximately 450 and 495 nanometres . Most blues contain a slight mixture of other colours; azure contains some green, while ultramarine contains some violet. The clear daytime sky and
4100-568: The Renaissance , to make the pigment ultramarine , the most expensive of all pigments. In the eighth century Chinese artists used cobalt blue to colour fine blue and white porcelain . In the Middle Ages , European artists used it in the windows of cathedrals . Europeans wore clothing coloured with the vegetable dye woad until it was replaced by the finer indigo from America. In the 19th century, synthetic blue dyes and pigments gradually replaced organic dyes and mineral pigments. Dark blue became
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4200-583: The Tyndall scattering of light in the stroma, an optical effect similar to what accounts for the blueness of the sky. The irises of the eyes of people with blue eyes contain less dark melanin than those of people with brown eyes, which means that they absorb less short-wavelength blue light, which is instead reflected out to the viewer. Eye colour also varies depending on the lighting conditions, especially for lighter-coloured eyes. Blue eyes are most common in Ireland,
4300-402: The iridophore cells in some fish and frogs. Blue eyes do not actually contain any blue pigment. Eye colour is determined by two factors: the pigmentation of the eye's iris and the scattering of light by the turbid medium in the stroma of the iris . In humans, the pigmentation of the iris varies from light brown to black. The appearance of blue, green, and hazel eyes results from
4400-425: The mandarin fish and the picturesque dragonet . More commonly, blueness in animals is a structural colouration ; an optical interference effect induced by organized nanometre-sized scales or fibres. Examples include the plumage of several birds like the blue jay and indigo bunting , the scales of butterflies like the morpho butterfly , collagen fibres in the skin of some species of monkey and opossum , and
4500-488: The solvated radius , which fits the framework of Prussian Blue. On the other hand, the sizes of solvated Na and Li are too large for the PB cavity, and the intercalation of these ions is hindered and much slower. The low and high voltage sets of peaks in the cyclic voltammetry correspond to 1 and ⅔ electron per Fe atom, respectively. The high voltage set is due to the Fe /Fe transition at
4600-452: The visible spectrum . He chose seven colours because that was the number of notes in the musical scale, which he believed was related to the optical spectrum. He included indigo , the hue between blue and violet, as one of the separate colours, though today it is usually considered a hue of blue. In painting and traditional colour theory , blue is one of the three primary colours of pigments (red, yellow, blue), which can be mixed to form
4700-424: The "500-mg Prussian blue capsules, when manufactured under the conditions of an approved New Drug Application, can be found safe and effective therapy" in certain poisoning cases. Radiogardase (Prussian blue insoluble capsules ) is a commercial product for the removal of caesium-137 from the intestine , so indirectly from the bloodstream by intervening in the enterohepatic circulation of caesium-137, reducing
4800-478: The 1870s when it became available in oil paint . The primary chemical constituent of the pigment is cobalt (II) stannate ( Co 2 SnO 4 ). The pigment is a greenish-blue colour. In watercolour, it has a slight chalkiness. When used in oil paint , it loses this quality. Today, cobalt chromate is sometimes marketed under the cerulean blue name but is darker and greener than the cobalt stannate version. The chromate makes excellent turquoise colours and
4900-712: The Islamic world, blue was the colour worn by Christians and Jews, because only Muslims were allowed to wear white and green. In the art and life of Europe during the early Middle Ages , blue played a minor role. This changed dramatically between 1130 and 1140 in Paris, when the Abbe Suger rebuilt the Saint Denis Basilica . Suger considered that light was the visible manifestation of the Holy Spirit. He installed stained glass windows coloured with cobalt , which, combined with
5000-646: The Romans, blue was the colour of mourning, as well as the colour of barbarians. The Celts and Germans reportedly dyed their faces blue to frighten their enemies, and tinted their hair blue when they grew old. The Romans made extensive use of indigo and Egyptian blue pigment, as evidenced, in part, by frescos in Pompeii . The Romans had many words for varieties of blue, including caeruleus , caesius , glaucus , cyaneus , lividus , venetus , aerius , and ferreus , but two words, both of foreign origin, became
5100-462: The United States, as of 2006, 1 out of every 6 people, or 16.6% of the total population, and 22.3% of the white population , have blue eyes, compared with about half of Americans born in 1900, and a third of Americans born in 1950. Blue eyes are becoming less common among American children . In the US, males are 3–5% more likely to have blue eyes than females. As early as the 7th millennium BC , lapis lazuli
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#17328589570915200-706: The Upper Paleolithic period, but not blue. Blue was also not used for dyeing fabric until long after red, ochre, pink, and purple. This is probably due to the perennial difficulty of making blue dyes and pigments. On the other hand, the rarity of blue pigment made it even more valuable. The earliest known blue dyes were made from plants – woad in Europe, indigo in Asia and Africa, while blue pigments were made from minerals, usually either lapis lazuli or azurite , and required more. Blue glazes posed still another challenge since
5300-577: The blue coat of the woman in her Summer's Day , 1879 in cerulean blue in conjunction with artificial ultramarine and cobalt blue . When the United Nations was formed at the end of World War II, they adopted cerulean blue for their emblem. The designer Oliver Lundquist stated that he chose the colour because it was "the opposite of red, the colour of war." In the Catholic Church, cerulean vestments are permitted on certain Marian feast days, primarily
5400-418: The blue wavelengths are scattered more widely by the oxygen and nitrogen molecules, and more blue comes to our eyes. This effect is called Rayleigh scattering , after Lord Rayleigh and confirmed by Albert Einstein in 1911. The sea is seen as blue for largely the same reason: the water absorbs the longer wavelengths of red and reflects and scatters the blue, which comes to the eye of the viewer. The deeper
5500-654: The cubic framework is built from Fe(II)–C–N–Fe(III) sequences, with Fe(II)–carbon distances of 1.92 Å and Fe(III)–nitrogen distances of 2.03 Å. One-fourth of the sites of Fe(CN) 6 subunits (supposedly at random) are vacant (empty), leaving three such groups on average per unit cell. The empty nitrogen sites are filled with water molecules instead, which are coordinated to Fe(III). The Fe(II) centers, which are low spin , are surrounded by six carbon ligands in an octahedral configuration. The Fe(III) centers, which are high spin , are octahedrally surrounded on average by 4.5 nitrogen atoms and 1.5 oxygen atoms (the oxygen from
5600-434: The deep sea appear blue because of an optical effect known as Rayleigh scattering . An optical effect called the Tyndall effect explains blue eyes . Distant objects appear more blue because of another optical effect called aerial perspective . Blue has been an important colour in art and decoration since ancient times. The semi-precious stone lapis lazuli was used in ancient Egypt for jewellery and ornament and later, in
5700-459: The early blue dyes and pigments were not thermally robust. In c. 2500 BC , the blue glaze Egyptian blue was introduced for ceramics, as well as many other objects. The Greeks imported indigo dye from India, calling it indikon, and they painted with Egyptian blue. Blue was not one of the four primary colours for Greek painting described by Pliny the Elder (red, yellow, black, and white). For
5800-481: The expensive lapis lazuli-derived ultramarine and was an important topic in the letters exchanged between Johann Leonhard Frisch and the president of the Prussian Academy of Sciences , Gottfried Wilhelm Leibniz , between 1708 and 1716. It is first mentioned in a letter written by Frisch to Leibniz, from March 31, 1708. Not later than 1708, Frisch began to promote and sell the pigment across Europe. By August 1709,
5900-501: The extremely expensive ultramarine made from lapis lazuli . Japanese painters and woodblock print artists , likewise, did not have access to a long-lasting blue pigment until they began to import Prussian blue from Europe. Prussian blue Fe 7 ( CN ) 18 (also ( Fe 4 [Fe(CN) 6 ] 3 ·xH 2 O ) was probably synthesized for the first time by the paint maker Johann Jacob Diesbach in Berlin around 1706. The pigment
6000-447: The first synthesis of Prussian blue. The story involves not only Diesbach, but also Johann Konrad Dippel . Diesbach was attempting to create a red lake pigment from cochineal, but obtained the blue instead as a result of the contaminated potash he was using. He borrowed the potash from Dippel, who had used it to produce his animal oil . No other known historical source mentions Dippel in this context. It is, therefore, difficult to judge
6100-532: The formula M 2 Fe[Fe(CN) 6 ] where M = Na or K . The iron in this material is all ferrous, hence the absence of deep color associated with the mixed valency. Oxidation of this white solid with hydrogen peroxide or sodium chlorate produces ferricyanide and affords Prussian blue. A "soluble" form, KFe [Fe (CN) 6 ] , which is really colloidal , can be made from potassium ferrocyanide and iron(III): The similar reaction of potassium ferricyanide and iron(II) results in
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#17328589570916200-491: The formula of his colour. In 1828, another scientist, Christian Gmelin then a professor of chemistry in Tübingen, found the process and published his formula. This was the beginning of new industry to manufacture artificial ultramarine, which eventually almost completely replaced the natural product. In 1878 German chemists synthesized indigo . This product rapidly replaced natural indigo, wiping out vast farms growing indigo. It
6300-487: The framework of potassium Prussian white provides favorable synergistic effects improving the long-term battery stability and increasing the number of possible recharge cycles, lengthening its service life. The large-size framework of Prussian white easily accommodating Na and K cations facilitates their intercalation and subsequent extraction during the charge/discharge cycles. The spacious and rigid host crystal structure contributes to its volumetric stability against
6400-448: The genus Nessaea , where blue is created by pterobilin . Other blue pigments of animal origin include phorcabilin, used by other butterflies in Graphium and Papilio (specifically P. phorcas and P. weiskei ), and sarpedobilin, which is used by Graphium sarpedon . Blue-pigmented organelles , known as "cyanosomes", exist in the chromatophores of at least two fish species,
6500-483: The infantry and artillery regiments of the Prussian Army . As Dunkelblau (dark blue), this shade achieved a symbolic importance and continued to be worn by most German soldiers for ceremonial and off-duty occasions until the outbreak of World War I , when it was superseded by greenish-gray field gray ( Feldgrau ). Prussian blue is produced by oxidation of ferrous ferrocyanide salts. These white solids have
6600-750: The internal residency time (and exposure) by about two-thirds. In particular, it was used to adsorb and remove Cs from those poisoned in the Goiânia accident in Brazil. Prussian blue is a common histopathology stain used by pathologists to detect the presence of iron in biopsy specimens, such as in bone marrow samples. The original stain formula, known historically (1867) as " Perls Prussian blue " after its inventor, German pathologist Max Perls (1843–1881), used separate solutions of potassium ferrocyanide and acid to stain tissue (these are now used combined, just before staining). Iron deposits in tissue then form
6700-413: The internal swelling stress and strain developing in sodium-batteries after many cycles. The material also offers perspectives of high energy densities (Ah/kg) while providing high recharge rate, even at low temperature. Prussian blue is a microcrystalline blue powder. It is insoluble, but the crystallites tend to form a colloid. Such colloids can pass through fine filters. Despite being one of
6800-614: The light from the red glass, filled the church with a bluish violet light. The church became the marvel of the Christian world , and the colour became known as the "bleu de Saint-Denis" . In the years that followed even more elegant blue stained glass windows were installed in other churches, including at Chartres Cathedral and Sainte-Chapelle in Paris. In the 12th century the Roman Catholic Church dictated that painters in Italy (and
6900-509: The light interferes destructively. Diverse colours therefore appear despite the absence of colourants. Egyptian blue , the first artificial pigment, was produced in the third millennium BC in Ancient Egypt. It is produced by heating pulverized sand, copper, and natron . It was used in tomb paintings and funereal objects to protect the dead in their afterlife. Prior to the 1700s, blue colourants for artwork were mainly based on lapis lazuli and
7000-456: The manufacture of wallpaper, and in the 19th century was widely used by French impressionist painters. Beginning in the 1820s, Prussian blue was imported into Japan through the port of Nagasaki . It was called bero-ai , or Berlin blue, and it became popular because it did not fade like traditional Japanese blue pigment, ai-gami , made from the dayflower . Prussian blue was used by both Hokusai , in his wave paintings, and Hiroshige . In 1799
7100-409: The marked high spots. Prussian blue is preferable because it will not abrade the extremely precise reference surfaces as many ground pigments may. Other uses include marking gear teeth during assembly to determine their interface characteristics. Prussian blue is formed in the Prussian blue assay for total phenols . Samples and phenolic standards are given acidic ferric chloride and ferricyanide, which
7200-584: The material. Engineer's blue and the pigment formed on cyanotypes —giving them their common name blueprints . Certain crayons were once colored with Prussian blue (later relabeled midnight blue ). Similarly, Prussian blue is the basis for laundry bluing . Nanoparticles of Prussian blue are used as pigments in some cosmetics ingredients, according to the European Union Observatory for Nanomaterials. Prussian blue's ability to incorporate monovalent metallic cations ( Me ) makes it useful as
7300-417: The more blue it often appears to the eye. For example, mountains in the distance often appear blue. This is the effect of atmospheric perspective ; the farther an object is away from the viewer, the less contrast there is between the object and its background colour, which is usually blue. In a painting where different parts of the composition are blue, green and red, the blue will appear to be more distant, and
7400-713: The most enduring; blavus , from the Germanic word blau , which eventually became bleu or blue; and azureus , from the Arabic word lazaward , which became azure. Blue was widely used in the decoration of churches in the Byzantine Empire. By contrast, in the Islamic world, blue was of secondary to green, believed to be the favourite colour of the Prophet Mohammed . At certain times in Moorish Spain and other parts of
7500-406: The name of Cölinblau . It was generally known as Höpfner blue from the late eighteenth century until the middle of the nineteenth century. In the late 1850s, art suppliers begin referring to the pigment as "ceruleum" blue. The London Times of 28 December 1859 had an advertisement for "Caeruleum, a new permanent colour prepared for the use of artists." Ure's Dictionary of Arts from 1875 describes
7600-427: The observer goes, the darker the blue becomes. In the open sea, only about 1% of light penetrates to a depth of 200 metres (see underwater and euphotic depth ). The colour of the sea is also affected by the colour of the sky, reflected by particles in the water; and by algae and plant life in the water, which can make it look green; or by sediment, which can make it look brown. The farther away an object is,
7700-502: The oldest known synthetic compounds, the composition of Prussian blue remained uncertain for many years. Its precise identification was complicated by three factors: The chemical formula of insoluble Prussian blue is Fe 7 (CN) 18 · x H 2 O , where x = 14–16. The structure was determined by using IR spectroscopy , Mössbauer spectroscopy , X-ray crystallography , and neutron crystallography . Since X-ray diffraction cannot easily distinguish carbon from nitrogen in
7800-568: The painting include cobalt and cerulean blue, with some areas of ultramarine . Laboratory analysis conducted by the National Gallery identified a relatively pure example of cerulean blue pigment in the shadows of the station's canopy. Researchers at the National Gallery suggested that "cerulean probably offered a pigment of sufficiently greenish tone to displace Prussian blue , which may not have been popular by this time." Berthe Morisot painted
7900-413: The pigment as "Caeruleum . . . consisting of stannate of protoxide of cobalt, mixed with stannic acid and sulphate of lime ." Cerulean was also referred to as coeurleum, cerulium, bleu céleste (celestial blue). Other nineteenth century English pigment names included "ceruleum blue" and "corruleum blue". By 1935, Max Doerner referred to the pigment as cerulean, as do most modern sources, though ceruleum
8000-604: The pigment had been termed Preussisch blau ; by November 1709, the German name Berlinisch Blau had been used for the first time by Frisch. Frisch himself is the author of the first known publication of Prussian blue in the paper Notitia Coerulei Berolinensis nuper inventi in 1710, as can be deduced from his letters. Diesbach had been working for Frisch since about 1701. To date, the Entombment of Christ , dated 1709 by Pieter van der Werff (Picture Gallery, Sanssouci , Potsdam)
8100-502: The plant kingdom". In the few plants that exploit structural colouration, brilliant colours are produced by structures within cells. The most brilliant blue colouration known in any living tissue is found in the marble berries of Pollia condensata , where a spiral structure of cellulose fibrils scattering blue light. The fruit of quandong ( Santalum acuminatum ) can appear blue owing to the same effect. Blue-pigmented animals are relatively rare. Examples of which include butterflies of
8200-574: The presence of heavier elements such as iron, the location of these lighter elements is deduced by spectroscopic means, as well as by observing the distances from the iron atom centers. Neutron diffraction can easily distinguish N and C atoms, and it has been used to determine the detailed structure of Prussian blue and its analogs. PB has a face centered cubic lattice structure, with four iron(III) ions per unit cell. "Soluble" PB crystals contain interstitial K ions; insoluble PB has interstitial water, instead. In ideal insoluble PB crystals,
8300-433: The purple Prussian blue dye in place, and are visualized as blue or purple deposits. Engineer's blue , Prussian blue in an oily base, is the traditional material used for spotting metal surfaces such as surface plates and bearings for hand scraping . A thin layer of nondrying paste is applied to a reference surface and transfers to the high spots of the workpiece. The toolmaker then scrapes, stones, or otherwise removes
8400-430: The red closer to the viewer. The cooler a colour is, the more distant it seems. Blue light is scattered more than other wavelengths by the gases in the atmosphere , hence our "blue planet". Some of the most desirable gems are blue, including sapphire and tanzanite . Compounds of copper(II) are characteristically blue and so are many copper-containing minerals. Azurite ( Cu 3 (CO 3 ) 2 (OH) 2 ) , with
8500-543: The reds and the blues so no one colour dominated the picture. Ultramarine was the most prestigious blue of the Renaissance, being more expensive than gold. Wealthy art patrons commissioned works with the most expensive blues possible. In 1616 Richard Sackville commissioned a portrait of himself by Isaac Oliver with three different blues, including ultramarine pigment for his stockings. Prussian blue Sodium ferrocyanide Prussian blue (also known as Berlin blue , Brandenburg blue , Parisian and Paris blue )
8600-472: The related mineral ultramarine. A breakthrough occurred in 1709 when German druggist and pigment maker Johann Jacob Diesbach discovered Prussian blue . The new blue arose from experiments involving heating dried blood with iron sulphides and was initially called Berliner Blau. By 1710 it was being used by the French painter Antoine Watteau , and later his successor Nicolas Lancret . It became immensely popular for
8700-441: The reliability of this story today. In 1724, the recipe was finally published by John Woodward. In 1752, French chemist Pierre J. Macquer made the important step of showing Prussian blue could be reduced to a salt of iron and a new acid, which could be used to reconstitute the dye. The new acid, hydrogen cyanide , first isolated from Prussian blue in pure form and characterized in 1782 by Swedish chemist Carl Wilhelm Scheele ,
8800-518: The rest of Europe consequently) to paint the Virgin Mary with blue, which became associated with holiness, humility and virtue. In medieval paintings, blue was used to attract the attention of the viewer to the Virgin Mary. Paintings of the mythical King Arthur began to show him dressed in blue. The coat of arms of the kings of France became an azure or light blue shield, sprinkled with golden fleur-de-lis or lilies. Blue had come from obscurity to become
8900-400: The royal colour. Blue came into wider use beginning in the Renaissance, when artists began to paint the world with perspective, depth, shadows, and light from a single source. In Renaissance paintings, artists tried to create harmonies between blue and red, lightening the blue with lead white paint and adding shadows and highlights. Raphael was a master of this technique, carefully balancing
9000-424: The same across several other countries, including China, Malaysia, and Indonesia. Past surveys in the US and Europe have found that blue is the colour most commonly associated with harmony , confidence , masculinity , knowledge , intelligence , calmness , distance , infinity , the imagination , cold , and sadness . The modern English word blue comes from Middle English bleu or blewe , from
9100-487: The same colloidal solution, because [Fe (CN) 6 ] is converted into ferrocyanide. The "insoluble" Prussian blue is obtained if, in the reactions above, an excess of Fe(III) is added: Despite the fact that it is prepared from cyanide salts, Prussian blue is not toxic because the cyanide groups are tightly bound to iron. Both ferrocyanide (( Fe (CN) 6 ) ) and ferricyanide (( Fe (CN) 6 ) ) are particularly stable and non-toxic polymeric cyanometalates due to
9200-617: The same word to describe blue and green. For example, in Vietnamese , the colour of both tree leaves and the sky is xanh . In Japanese, the word for blue ( 青 , ao ) is often used for colours that English speakers would refer to as green, such as the colour of a traffic signal meaning "go". In Lakota, the word tȟó is used for both blue and green, the two colours not being distinguished in older Lakota (for more on this subject, see Blue–green distinction in language ). Linguistic research indicates that languages do not begin by having
9300-460: The silica prior to firing. The cobalt occupies sites otherwise filled with silicon. Methyl blue is the dominant blue pigment in inks used in pens. Blueprinting involves the production of Prussian blue in situ. Certain metal ions characteristically form blue solutions or blue salts. Of some practical importance, cobalt is used to make the deep blue glazes and glasses. It substitutes for silicon or aluminum ions in these materials. Cobalt
9400-410: The six coordinated water molecules). Around eight (interstitial) water molecules are present in the unit cell, either as isolated molecules or hydrogen bonded to the coordinated water. It is worth noting that in soluble hexacyanoferrates Fe(II or III) is always coordinated to the carbon atom of a cyanide , whereas in crystalline Prussian blue Fe ions are coordinated to both C and N. The composition
9500-446: The strong iron coordination to cyanide ions. Although cyanide bonds well with transition metals in general like chromium, these non-iron coordination compounds are not as stable as iron cyanides, therefore increasing the risk of releasing CN ions, and subsequently comparative toxicity. In former times, the addition of iron(II) salts to a solution of ferricyanide was thought to afford a material different from Prussian blue. The product
9600-620: Was eventually given the name Blausäure (literally "blue acid") because of its derivation from Prussian blue, and in English became known popularly as Prussic acid. Cyanide , a colorless anion that forms in the process of making Prussian blue, derives its name from the Greek word for dark blue. In the late 1800s, Rabbi Gershon Henoch Leiner , the Hasidic Rebbe of Radzin , dyed tzitziyot with Prussian blue made with sepia , believing that this
9700-674: Was mined in the Sar-i Sang mines, in Shortugai , and in other mines in Badakhshan province in northeast Afghanistan . Lapis lazuli artifacts, dated to 7570 BC, have been found at Bhirrana , which is the oldest site of Indus Valley civilisation . Lapis was highly valued by the Indus Valley Civilisation (7570–1900 BC). Lapis beads have been found at Neolithic burials in Mehrgarh ,
9800-431: Was the true techeiles dye. Even though some have questioned its identity as techeiles because of its artificial production, and claimed that had Rabbi Leiner been aware of this he would have retracted his position that his dye was techeiles, others have disputed this and claimed that Rabbi Leiner would not have retracted. From the beginning of the 18th century, Prussian blue was the predominant uniform coat color worn by
9900-400: Was traditionally named Turnbull's blue (TB). X-ray diffraction and electron diffraction methods have shown, though, that the structures of PB and TB are identical. The differences in the colors for TB and PB reflect subtle differences in the methods of precipitation, which strongly affect particle size and impurity content. Prussian white, also known as Berlin white or Everett's salt ,
10000-400: Was used in oil paint. It was popular with artists including Claude Monet , Paul Signac , and Picasso . Van Gogh created his own approximation of cerulean blue using a mixture of cobalt blue , cadmium yellow , and white. In 1877, Monet had added the pigment to his palette, using it in a painting from his series La Gare Saint-Lazare (now in the National Gallery, London). The blues in
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