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71-551: The formation is mostly reddish-brown clay -rich siltstone and fine-grained sandstone , with sandstone beds up to 20 feet (6.1 m) thick. The formation also contains conglomerate lenses up to 20 feet (6.1 m). The total thickness of the formation is 550 feet (170 m). The formation unconformably overlies the Baldy Hill Formation and underlies the Sloan Canyon Formation or locally

142-400: A base catalyst . The base abstracts a proton from a weak acid to give an intermediate that goes on to react with another reagent. Common substrates for proton abstraction are alcohols , phenols , amines , and carbon acids . The p K a value for dissociation of a C–H bond is extremely high, but the pK a alpha hydrogens of a carbonyl compound are about 3 log units lower. Typical p K

213-527: A catalyst . The hydroxide ion forms salts , some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical . The corresponding electrically neutral compound HO is the hydroxyl radical . The corresponding covalently bound group  –OH of atoms is the hydroxy group . Both the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry . Many inorganic substances which bear

284-409: A basic hydroxide of aluminium , is the principal ore from which the metal is manufactured. Similarly, goethite (α-FeO(OH)) and lepidocrocite (γ-FeO(OH)), basic hydroxides of iron , are among the principal ores used for the manufacture of metallic iron. Aside from NaOH and KOH, which enjoy very large scale applications, the hydroxides of the other alkali metals also are useful. Lithium hydroxide

355-463: A bridging hydroxide tends to be at a lower frequency as in [( bipyridine )Cu(OH) 2 Cu( bipyridine )] (955 cm ). M−OH stretching vibrations occur below about 600 cm . For example, the tetrahedral ion [Zn(OH) 4 ] has bands at 470 cm ( Raman -active, polarized) and 420 cm (infrared). The same ion has a (HO)–Zn–(OH) bending vibration at 300 cm . Sodium hydroxide solutions, also known as lye and caustic soda, are used in

426-575: A gel of orthosilicic acid ).) The clay minerals formed depend on the composition of the source rock and the climate. Acid weathering of feldspar -rich rock, such as granite , in warm climates tends to produce kaolin. Weathering of the same kind of rock under alkaline conditions produces illite . Smectite forms by weathering of igneous rock under alkaline conditions, while gibbsite forms by intense weathering of other clay minerals. There are two types of clay deposits: primary and secondary. Primary clays form as residual deposits in soil and remain at

497-836: A great capacity to take up water, and they increase greatly in volume when they do so. When dried, they shrink back to their original volume. This produces distinctive textures, such as mudcracks or "popcorn" texture, in clay deposits. Soils containing swelling clay minerals (such as bentonite ) pose a considerable challenge for civil engineering, because swelling clay can break foundations of buildings and ruin road beds. Clay minerals most commonly form by prolonged chemical weathering of silicate-bearing rocks. They can also form locally from hydrothermal activity. Chemical weathering takes place largely by acid hydrolysis due to low concentrations of carbonic acid , dissolved in rainwater or released by plant roots. The acid breaks bonds between aluminium and oxygen, releasing other metal ions and silica (as

568-415: A kind of close-packing of magnesium and hydroxide ions. The amphoteric hydroxide Al(OH) 3 has four major crystalline forms: gibbsite (most stable), bayerite , nordstrandite , and doyleite . All these polymorphs are built up of double layers of hydroxide ions – the aluminium atoms on two-thirds of the octahedral holes between the two layers – and differ only in the stacking sequence of

639-484: A layered structure, made up of tetrahedral Li(OH) 4 and (OH)Li 4 units. This is consistent with the weakly basic character of LiOH in solution, indicating that the Li–OH bond has much covalent character. The hydroxide ion displays cylindrical symmetry in hydroxides of divalent metals Ca, Cd, Mn, Fe, and Co. For example, magnesium hydroxide Mg(OH) 2 ( brucite ) crystallizes with the cadmium iodide layer structure, with

710-402: A major challenge in civil engineering . The defining mechanical property of clay is its plasticity when wet and its ability to harden when dried or fired. Clays show a broad range of water content within which they are highly plastic, from a minimum water content (called the plastic limit ) where the clay is just moist enough to mould, to a maximum water content (called the liquid limit) where

781-429: A reddish or brownish colour from small amounts of iron oxide . Clays develop plasticity when wet but can be hardened through firing . Clay is the longest-known ceramic material. Prehistoric humans discovered the useful properties of clay and used it for making pottery . Some of the earliest pottery shards have been dated to around 14,000 BCE, and clay tablets were the first known writing medium. Clay

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852-452: Is Armenian bole , which is used to soothe an upset stomach. Some animals such as parrots and pigs ingest clay for similar reasons. Kaolin clay and attapulgite have been used as anti-diarrheal medicines. Clay as the defining ingredient of loam is one of the oldest building materials on Earth , among other ancient, naturally occurring geologic materials such as stone and organic materials like wood. Between one-half and two-thirds of

923-429: Is amphoteric . The hydroxide itself is insoluble in water, with a solubility product log  K * sp of −11.7. Addition of acid gives soluble hydrolysis products, including the trimeric ion [Be 3 (OH) 3 (H 2 O) 6 ] , which has OH groups bridging between pairs of beryllium ions making a 6-membered ring. At very low pH the aqua ion [Be(H 2 O) 4 ] is formed. Addition of hydroxide to Be(OH) 2 gives

994-438: Is a basic lead carbonate, (PbCO 3 ) 2 ·Pb(OH) 2 , which has been used as a white pigment because of its opaque quality, though its use is now restricted because it can be a source for lead poisoning . The hydroxide ion appears to rotate freely in crystals of the heavier alkali metal hydroxides at higher temperatures so as to present itself as a spherical ion, with an effective ionic radius of about 153 pm. Thus,

1065-446: Is a strong base, with a p K b of −0.36. Lithium hydroxide is used in breathing gas purification systems for spacecraft , submarines , and rebreathers to remove carbon dioxide from exhaled gas. The hydroxide of lithium is preferred to that of sodium because of its lower mass. Sodium hydroxide , potassium hydroxide , and the hydroxides of the other alkali metals are also strong bases . Beryllium hydroxide Be(OH) 2

1136-507: Is a strong base. Carbon forms no simple hydroxides. The hypothetical compound C(OH) 4 ( orthocarbonic acid or methanetetrol) is unstable in aqueous solution: Carbon dioxide is also known as carbonic anhydride, meaning that it forms by dehydration of carbonic acid H 2 CO 3 (OC(OH) 2 ). Silicic acid is the name given to a variety of compounds with a generic formula [SiO x (OH) 4−2 x ] n . Orthosilicic acid has been identified in very dilute aqueous solution. It

1207-620: Is a unique type of marine clay indigenous to the glaciated terrains of Norway , North America , Northern Ireland , and Sweden . It is a highly sensitive clay, prone to liquefaction , and has been involved in several deadly landslides . Modelling clay is used in art and handicraft for sculpting . Clays are used for making pottery , both utilitarian and decorative, and construction products, such as bricks, walls, and floor tiles. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware, stoneware, and porcelain. Prehistoric humans discovered

1278-411: Is a weak acid with p K a1  = 9.84, p K a2  = 13.2 at 25 °C. It is usually written as H 4 SiO 4 , but the formula Si(OH) 4 is generally accepted. Other silicic acids such as metasilicic acid (H 2 SiO 3 ), disilicic acid (H 2 Si 2 O 5 ), and pyrosilicic acid (H 6 Si 2 O 7 ) have been characterized. These acids also have hydroxide groups attached to

1349-459: Is clay with visible annual layers that are formed by seasonal deposition of those layers and are marked by differences in erosion and organic content. This type of deposit is common in former glacial lakes . When fine sediments are delivered into the calm waters of these glacial lake basins away from the shoreline, they settle to the lake bed. The resulting seasonal layering is preserved in an even distribution of clay sediment banding. Quick clay

1420-407: Is formed together with some basic hydroxo complexes. The structure of [Sn 3 (OH) 4 ] has a triangle of tin atoms connected by bridging hydroxide groups. Tin(IV) hydroxide is unknown but can be regarded as the hypothetical acid from which stannates, with a formula [Sn(OH) 6 ] , are derived by reaction with the (Lewis) basic hydroxide ion. Hydrolysis of Pb in aqueous solution is accompanied by

1491-674: Is important to soil fertility. Clay is a common component of sedimentary rock . Shale is formed largely from clay and is the most common of sedimentary rocks. However, most clay deposits are impure. Many naturally occurring deposits include both silts and clay. Clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts , which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in particle size and other physical properties. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider

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1562-415: Is known as limewater and can be used to test for the weak acid carbon dioxide. The reaction Ca(OH) 2 + CO 2 ⇌ Ca + HCO 3 + OH illustrates the basicity of calcium hydroxide. Soda lime , which is a mixture of the strong bases NaOH and KOH with Ca(OH) 2 , is used as a CO 2 absorbent. The simplest hydroxide of boron B(OH) 3 , known as boric acid , is an acid. Unlike the hydroxides of

1633-406: Is manipulated by careful control of temperature and alkali concentration. In the first phase, aluminium dissolves in hot alkaline solution as Al(OH) 4 , but other hydroxides usually present in the mineral, such as iron hydroxides, do not dissolve because they are not amphoteric. After removal of the insolubles, the so-called red mud , pure aluminium hydroxide is made to precipitate by reducing

1704-502: Is often written with the formula H 2 TeO 4 ·2H 2 O but is better described structurally as Te(OH) 6 . Ortho -periodic acid can lose all its protons, eventually forming the periodate ion [IO 4 ] . It can also be protonated in strongly acidic conditions to give the octahedral ion [I(OH) 6 ] , completing the isoelectronic series, [E(OH) 6 ] , E = Sn, Sb, Te, I; z = −2, −1, 0, +1. Other acids of iodine(VII) that contain hydroxide groups are known, in particular in salts such as

1775-512: Is used in many industrial processes, such as paper making, cement production, and chemical filtering . Bentonite clay is widely used as a mold binder in the manufacture of sand castings . Clay is a common filler used in polymer nanocomposites . It can reduce the cost of the composite, as well as impart modified behavior: increased stiffness , decreased permeability , decreased electrical conductivity , etc. Traditional uses of clay as medicine go back to prehistoric times. An example

1846-886: Is used in many modern industrial processes, such as paper making, cement production, and chemical filtering . Between one-half and two-thirds of the world's population live or work in buildings made with clay, often baked into brick, as an essential part of its load-bearing structure. Clay is a very common substance. Shale , formed largely from clay, is the most common sedimentary rock. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts , which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. Mixtures of sand , silt and less than 40% clay are called loam . Soils high in swelling clays ( expansive clay ), which are clay minerals that readily expand in volume when they absorb water, are

1917-417: Is very dependent on the total aluminium concentration. Various other hydroxo complexes are found in crystalline compounds. Perhaps the most important is the basic hydroxide AlO(OH), a polymeric material known by the names of the mineral forms boehmite or diaspore , depending on crystal structure. Gallium hydroxide , indium hydroxide , and thallium(III) hydroxide are also amphoteric. Thallium(I) hydroxide

1988-655: The Exeter Sandstone . The formation is usually assigned to the Dockum Group . The proposal of Spencer G. Lucas and his collaborators to abandon the Dockum Group, possibly in favor of the Chinle Group , is highly controversial. A fossil phytosaur skull and metoposaurids have been found in the formation. The formation was first named by Baldwin and Muelberger in 1959. Lucas et al. rejected

2059-471: The band width increases when the OH group is involved in hydrogen bonding. A water molecule has an HOH bending mode at about 1600 cm , so the absence of this band can be used to distinguish an OH group from a water molecule. When the OH group is bound to a metal ion in a coordination complex , an M−OH bending mode can be observed. For example, in [Sn(OH) 6 ] it occurs at 1065 cm . The bending mode for

2130-568: The hydrolysis reaction Although the base strength of sodium carbonate solutions is lower than a concentrated sodium hydroxide solution, it has the advantage of being a solid. It is also manufactured on a vast scale (42 million tonnes in 2005) by the Solvay process . An example of the use of sodium carbonate as an alkali is when washing soda (another name for sodium carbonate) acts on insoluble esters, such as triglycerides , commonly known as fats, to hydrolyze them and make them soluble. Bauxite ,

2201-399: The meso periodate ion that occurs in K 4 [I 2 O 8 (OH) 2 ]·8H 2 O. As is common outside of the alkali metals, hydroxides of the elements in lower oxidation states are complicated. For example, phosphorous acid H 3 PO 3 predominantly has the structure OP(H)(OH) 2 , in equilibrium with a small amount of P(OH) 3 . The oxoacids of chlorine , bromine , and iodine have

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2272-445: The active site. Solutions containing the hydroxide ion attack glass . In this case, the silicates in glass are acting as acids. Basic hydroxides, whether solids or in solution, are stored in airtight plastic containers. The hydroxide ion can function as a typical electron-pair donor ligand , forming such complexes as tetrahydroxoaluminate/tetrahydroxido aluminate [Al(OH) 4 ] . It is also often found in mixed-ligand complexes of

2343-521: The alkali and alkaline earth hydroxides, it does not dissociate in aqueous solution. Instead, it reacts with water molecules acting as a Lewis acid, releasing protons. A variety of oxyanions of boron are known, which, in the protonated form, contain hydroxide groups. Aluminium hydroxide Al(OH) 3 is amphoteric and dissolves in alkaline solution. In the Bayer process for the production of pure aluminium oxide from bauxite minerals this equilibrium

2414-407: The assignment of the formation to the Dockum Group and adjusted the lower contact. Clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite , Al 2 Si 2 O 5 ( OH ) 4 ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as

2485-526: The bichromate ion [HCrO 4 ] dissociates according to with a p K a of about 5.9. The infrared spectra of compounds containing the OH functional group have strong absorption bands in the region centered around 3500 cm . The high frequency of molecular vibration is a consequence of the small mass of the hydrogen atom as compared to the mass of the oxygen atom, and this makes detection of hydroxyl groups by infrared spectroscopy relatively easy. A band due to an OH group tends to be sharp. However,

2556-445: The chloride salt of a tetrameric cation [Zr 4 (OH) 8 (H 2 O) 16 ] in which there is a square of Zr ions with two hydroxide groups bridging between Zr atoms on each side of the square and with four water molecules attached to each Zr atom. The mineral malachite is a typical example of a basic carbonate. The formula, Cu 2 CO 3 (OH) 2 shows that it is halfway between copper carbonate and copper hydroxide . Indeed, in

2627-415: The cohesion that makes it plastic. In kaolinite clay, the bonding between plates is provided by a film of water molecules that hydrogen bond the plates together. The bonds are weak enough to allow the plates to slip past each other when the clay is being moulded, but strong enough to hold the plates in place and allow the moulded clay to retain its shape after it is moulded. When the clay is dried, most of

2698-444: The equal charge constraint. The pH of a solution is equal to the decimal cologarithm of the hydrogen cation concentration; the pH of pure water is close to 7 at ambient temperatures. The concentration of hydroxide ions can be expressed in terms of pOH , which is close to (14 − pH), so the pOH of pure water is also close to 7. Addition of a base to water will reduce the hydrogen cation concentration and therefore increase

2769-516: The first known writing medium. Clay was chosen due to the local material being easy to work with and widely available. Scribes wrote on the tablets by inscribing them with a script known as cuneiform , using a blunt reed called a stylus , which effectively produced the wedge shaped markings of their writing. After being written on, clay tablets could be reworked into fresh tablets and reused if needed, or fired to make them permanent records. Purpose-made clay balls were used as sling ammunition . Clay

2840-400: The formation of various hydroxo-containing complexes, some of which are insoluble. The basic hydroxo complex [Pb 6 O(OH) 6 ] is a cluster of six lead centres with metal–metal bonds surrounding a central oxide ion. The six hydroxide groups lie on the faces of the two external Pb 4 tetrahedra. In strongly alkaline solutions soluble plumbate ions are formed, including [Pb(OH) 6 ] . In

2911-544: The formula O ⁠ n −1 / 2 ⁠ A(OH), where n is the oxidation number : +1, +3, +5, or +7, and A = Cl, Br, or I. The only oxoacid of fluorine is F(OH), hypofluorous acid . When these acids are neutralized the hydrogen atom is removed from the hydroxide group. The hydroxides of the transition metals and post-transition metals usually have the metal in the +2 (M = Mn, Fe, Co, Ni, Cu, Zn) or +3 (M = Fe, Ru, Rh, Ir) oxidation state. None are soluble in water, and many are poorly defined. One complicating feature of

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2982-534: The formula suggests these substances contain M(OH) 6 octahedral structural units. Layered double hydroxides may be represented by the formula [M 1− x M x (OH) 2 ] (X ) q ⁄ n · y H 2 O . Most commonly, z  = 2, and M = Ca , Mg , Mn , Fe , Co , Ni , Cu , or Zn ; hence q  =  x . Potassium hydroxide and sodium hydroxide are two well-known reagents in organic chemistry . The hydroxide ion may act as

3053-431: The high-temperature forms of KOH and NaOH have the sodium chloride structure, which gradually freezes in a monoclinically distorted sodium chloride structure at temperatures below about 300 °C. The OH groups still rotate even at room temperature around their symmetry axes and, therefore, cannot be detected by X-ray diffraction . The room-temperature form of NaOH has the thallium iodide structure. LiOH, however, has

3124-512: The higher oxidation states of the pnictogens , chalcogens , halogens , and noble gases there are oxoacids in which the central atom is attached to oxide ions and hydroxide ions. Examples include phosphoric acid H 3 PO 4 , and sulfuric acid H 2 SO 4 . In these compounds one or more hydroxide groups can dissociate with the liberation of hydrogen cations as in a standard Brønsted–Lowry acid. Many oxoacids of sulfur are known and all feature OH groups that can dissociate. Telluric acid

3195-421: The hydroxide ion concentration (decrease pH, increase pOH) even if the base does not itself contain hydroxide. For example, ammonia solutions have a pH greater than 7 due to the reaction NH 3 + H ⇌ NH 4 , which decreases the hydrogen cation concentration, which increases the hydroxide ion concentration. pOH can be kept at a nearly constant value with various buffer solutions . In an aqueous solution

3266-488: The hydroxide ion is a base in the Brønsted–Lowry sense as it can accept a proton from a Brønsted–Lowry acid to form a water molecule. It can also act as a Lewis base by donating a pair of electrons to a Lewis acid. In aqueous solution both hydrogen and hydroxide ions are strongly solvated, with hydrogen bonds between oxygen and hydrogen atoms. Indeed, the bihydroxide ion H 3 O 2 has been characterized in

3337-475: The hydroxide ion reacts rapidly with atmospheric carbon dioxide , acting as an acid, to form, initially, the bicarbonate ion. The equilibrium constant for this reaction can be specified either as a reaction with dissolved carbon dioxide or as a reaction with carbon dioxide gas (see Carbonic acid for values and details). At neutral or acid pH, the reaction is slow, but is catalyzed by the enzyme carbonic anhydrase , which effectively creates hydroxide ions at

3408-473: The hydroxides is their tendency to undergo further condensation to the oxides, a process called olation . Hydroxides of metals in the +1 oxidation state are also poorly defined or unstable. For example, silver hydroxide Ag(OH) decomposes spontaneously to the oxide (Ag 2 O). Copper(I) and gold(I) hydroxides are also unstable, although stable adducts of CuOH and AuOH are known. The polymeric compounds M(OH) 2 and M(OH) 3 are in general prepared by increasing

3479-407: The layers. The structures are similar to the brucite structure. However, whereas the brucite structure can be described as a close-packed structure in gibbsite the OH groups on the underside of one layer rest on the groups of the layer below. This arrangement led to the suggestion that there are directional bonds between OH groups in adjacent layers. This is an unusual form of hydrogen bonding since

3550-434: The manufacture of pulp and paper , textiles , drinking water , soaps and detergents , and as a drain cleaner . Worldwide production in 2004 was approximately 60 million tonnes . The principal method of manufacture is the chloralkali process . Solutions containing the hydroxide ion are generated when a salt of a weak acid is dissolved in water. Sodium carbonate is used as an alkali, for example, by virtue of

3621-404: The material. The clay mineral kaolinite is transformed into a non-clay material, metakaolin , which remains rigid and hard if moistened again. Further firing through the stoneware and porcelain stages further recrystallizes the metakaolin into yet stronger minerals such as mullite . The tiny size and plate form of clay particles gives clay minerals a high surface area. In some clay minerals,

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3692-724: The moulded clay is just dry enough to hold its shape. The plastic limit of kaolinite clay ranges from about 36% to 40% and its liquid limit ranges from about 58% to 72%. High-quality clay is also tough, as measured by the amount of mechanical work required to roll a sample of clay flat. Its toughness reflects a high degree of internal cohesion. Clay has a high content of clay minerals that give it its plasticity. Clay minerals are hydrous aluminium phyllosilicate minerals , composed of aluminium and silicon ions bonded into tiny, thin plates by interconnecting oxygen and hydroxide ions. These plates are tough but flexible, and in moist clay, they adhere to each other. The resulting aggregates give clay

3763-442: The pH of an aqueous solutions of the corresponding metal cations until the hydroxide precipitates out of solution. On the converse, the hydroxides dissolve in acidic solution. Zinc hydroxide Zn(OH) 2 is amphoteric, forming the tetrahydroxido zincate ion Zn(OH) 4 in strongly alkaline solution. Numerous mixed ligand complexes of these metals with the hydroxide ion exist. In fact, these are in general better defined than

3834-480: The past the formula was written as CuCO 3 ·Cu(OH) 2 . The crystal structure is made up of copper, carbonate and hydroxide ions. The mineral atacamite is an example of a basic chloride. It has the formula, Cu 2 Cl(OH) 3 . In this case the composition is nearer to that of the hydroxide than that of the chloride CuCl 2 ·3Cu(OH) 2 . Copper forms hydroxyphosphate ( libethenite ), arsenate ( olivenite ), sulfate ( brochantite ), and nitrate compounds. White lead

3905-467: The plates carry a negative electrical charge that is balanced by a surrounding layer of positive ions ( cations ), such as sodium, potassium, or calcium. If the clay is mixed with a solution containing other cations, these can swap places with the cations in the layer around the clay particles, which gives clays a high capacity for ion exchange . The chemistry of clay minerals, including their capacity to retain nutrient cations such as potassium and ammonium,

3976-402: The process of olation , forming polyoxometalates . In some cases, the products of partial hydrolysis of metal ion, described above, can be found in crystalline compounds. A striking example is found with zirconium (IV). Because of the high oxidation state, salts of Zr are extensively hydrolyzed in water even at low pH. The compound originally formulated as ZrOCl 2 ·8H 2 O was found to be

4047-408: The removal of heavy metals from waste water and air purification. Hydroxide Hydroxide is a diatomic anion with chemical formula OH . It consists of an oxygen and hydrogen atom held together by a single covalent bond , and carries a negative electric charge . It is an important but usually minor constituent of water . It functions as a base , a ligand , a nucleophile , and

4118-696: The separation to occur at a particle size of 2 μm (clays being finer than silts), sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Clay-size particles and clay minerals are not the same, despite a degree of overlap in their respective definitions. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits . ISO 14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. Mixtures of sand , silt and less than 40% clay are called loam . Some clay minerals (such as smectite ) are described as swelling clay minerals, because they have

4189-400: The silicon; the formulas suggest that these acids are protonated forms of poly oxyanions . Few hydroxo complexes of germanium have been characterized. Tin(II) hydroxide Sn(OH) 2 was prepared in anhydrous media. When tin(II) oxide is treated with alkali the pyramidal hydroxo complex Sn(OH) 3 is formed. When solutions containing this ion are acidified, the ion [Sn 3 (OH) 4 ]

4260-550: The simpler derivatives. Many can be made by deprotonation of the corresponding metal aquo complex . Vanadic acid H 3 VO 4 shows similarities with phosphoric acid H 3 PO 4 though it has a much more complex vanadate oxoanion chemistry. Chromic acid H 2 CrO 4 , has similarities with sulfuric acid H 2 SO 4 ; for example, both form acid salts A [HMO 4 ] . Some metals, e.g. V, Cr, Nb, Ta, Mo, W, tend to exist in high oxidation states. Rather than forming hydroxides in aqueous solution, they convert to oxo clusters by

4331-841: The site of formation. Secondary clays are clays that have been transported from their original location by water erosion and deposited in a new sedimentary deposit. Secondary clay deposits are typically associated with very low energy depositional environments such as large lakes and marine basins. The main groups of clays include kaolinite , montmorillonite - smectite , and illite . Chlorite , vermiculite , talc , and pyrophyllite are sometimes also classified as clay minerals. There are approximately 30 different types of "pure" clays in these categories, but most "natural" clay deposits are mixtures of these different types, along with other weathered minerals. Clay minerals in clays are most easily identified using X-ray diffraction rather than chemical or physical tests. Varve (or varved clay )

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4402-499: The solid state. This compound is centrosymmetric and has a very short hydrogen bond (114.5  pm ) that is similar to the length in the bifluoride ion HF 2 (114 pm). In aqueous solution the hydroxide ion forms strong hydrogen bonds with water molecules. A consequence of this is that concentrated solutions of sodium hydroxide have high viscosity due to the formation of an extended network of hydrogen bonds as in hydrogen fluoride solutions. In solution, exposed to air,

4473-482: The soluble tetrahydroxoberyllate or tetrahydroxido beryllate anion, [Be(OH) 4 ] . The solubility in water of the other hydroxides in this group increases with increasing atomic number . Magnesium hydroxide Mg(OH) 2 is a strong base (up to the limit of its solubility, which is very low in pure water), as are the hydroxides of the heavier alkaline earths: calcium hydroxide , strontium hydroxide , and barium hydroxide . A solution or suspension of calcium hydroxide

4544-429: The temperature and adding water to the extract, which, by diluting the alkali, lowers the pH of the solution. Basic aluminium hydroxide AlO(OH), which may be present in bauxite, is also amphoteric. In mildly acidic solutions, the hydroxo/hydroxido complexes formed by aluminium are somewhat different from those of boron, reflecting the greater size of Al(III) vs. B(III). The concentration of the species [Al 13 (OH) 32 ]

4615-653: The two hydroxide ion involved would be expected to point away from each other. The hydrogen atoms have been located by neutron diffraction experiments on α-AlO(OH) ( diaspore ). The O–H–O distance is very short, at 265 pm; the hydrogen is not equidistant between the oxygen atoms and the short OH bond makes an angle of 12° with the O–O line. A similar type of hydrogen bond has been proposed for other amphoteric hydroxides, including Be(OH) 2 , Zn(OH) 2 , and Fe(OH) 3 . A number of mixed hydroxides are known with stoichiometry A 3 M (OH) 6 , A 2 M (OH) 6 , and AM (OH) 6 . As

4686-485: The type [ML x (OH) y ] , where L is a ligand. The hydroxide ion often serves as a bridging ligand , donating one pair of electrons to each of the atoms being bridged. As illustrated by [Pb 2 (OH)] , metal hydroxides are often written in a simplified format. It can even act as a 3-electron-pair donor, as in the tetramer [PtMe 3 (OH)] 4 . When bound to a strongly electron-withdrawing metal centre, hydroxide ligands tend to ionise into oxide ligands. For example,

4757-548: The useful properties of clay. Some of the earliest pottery shards recovered are from central Honshu , Japan . They are associated with the Jōmon culture, and recovered deposits have been dated to around 14,000 BCE. Cooking pots, art objects, dishware, smoking pipes , and even musical instruments such as the ocarina can all be shaped from clay before being fired. Ancient peoples in Mesopotamia adopted clay tablets as

4828-426: The water molecules are removed, and the plates hydrogen bond directly to each other, so that the dried clay is rigid but still fragile. If the clay is moistened again, it will once more become plastic. When the clay is fired to the earthenware stage, a dehydration reaction removes additional water from the clay, causing clay plates to irreversibly adhere to each other via stronger covalent bonding , which strengthens

4899-426: The word hydroxide in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxy groups . The hydroxide ion is naturally produced from water by the self-ionization reaction: The equilibrium constant for this reaction, defined as has a value close to 10 at 25 °C, so the concentration of hydroxide ions in pure water is close to 10  mol∙dm , to satisfy

4970-493: The world's population, in both traditional societies as well as developed countries, still live or work in buildings made with clay, often baked into brick, as an essential part of their load-bearing structure. Also a primary ingredient in many natural building techniques, clay is used to create adobe , cob , cordwood , and structures and building elements such as wattle and daub , clay plaster, clay render case, clay floors and clay paints and ceramic building material . Clay

5041-461: Was used as a mortar in brick chimneys and stone walls where protected from water. Clay, relatively impermeable to water, is also used where natural seals are needed, such as in pond linings, the cores of dams , or as a barrier in landfills against toxic seepage (lining the landfill, preferably in combination with geotextiles ). Studies in the early 21st century have investigated clay's absorption capacities in various applications, such as

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