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69-555: Muscovite (also known as common mica , isinglass , or potash mica ) is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl 2 (Al Si 3 O 10 )( F ,O H ) 2 , or ( KF ) 2 ( Al 2 O 3 ) 3 ( SiO 2 ) 6 ( H 2 O ). It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets) which are often highly elastic . Sheets of muscovite 5 meters × 3 meters (16.5 feet × 10 feet) have been found in Nellore , India . Muscovite has

138-430: A Mohs hardness of 2–2.25 parallel to the [001] face, 4 perpendicular to the [001] and a specific gravity of 2.76–3. It can be colorless or tinted through grays, violet or red, and can be transparent or translucent. It is anisotropic and has high birefringence . Its crystal system is monoclinic . The green, chromium -rich variety is called fuchsite ; mariposite is also a chromium-rich type of muscovite. Muscovite

207-464: A TOT-c structure. In other words, a crystal of muscovite consists of layers ( TOT ) bonded to each other by potassium cations ( c ). Each layer is composed of three sheets. The outer sheets ('T' or tetrahedral sheets) consist of silicon-oxygen tetrahedra and aluminium -oxygen tetrahedra, with three of the oxygen anions of each tetrahedron shared with neighboring tetrahedra to form a hexagonal sheet. The fourth oxygen anion in each tetrahedral sheet

276-400: 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

345-409: 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

414-463: 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

483-415: 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

552-484: 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

621-420: A shared oxygen vertex—a silicon:oxygen ratio of 2:7. The Nickel–Strunz classification is 09.B. Examples include: Cyclosilicates (from Greek κύκλος kýklos 'circle'), or ring silicates, have three or more tetrahedra linked in a ring. The general formula is (Si x O 3 x ) , where one or more silicon atoms can be replaced by other 4-coordinated atom(s). The silicon:oxygen ratio is 1:3. Double rings have

690-403: 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

759-510: A three-dimensional framework of silicate tetrahedra with SiO 2 in a 1:2 ratio. This group comprises nearly 75% of the crust of the Earth . Tectosilicates, with the exception of the quartz group, are aluminosilicates . The Nickel–Strunz classifications are 09.F and 09.G, 04.DA (Quartz/ silica family). Examples include: Hydroxide Many inorganic substances which bear the word hydroxide in their names are not ionic compounds of

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828-417: A type of plankton known as diatoms construct their exoskeletons ("frustules") from silica extracted from seawater . The frustules of dead diatoms are a major constituent of deep ocean sediment , and of diatomaceous earth . A silicate mineral is generally an inorganic compound consisting of subunits with the formula [SiO 2+ n ] . Although depicted as such, the description of silicates as anions

897-552: A wide variety of electronics and as a filler in paints, plastic, and wallboard . It lends a silky luster to wallpaper . It is also used in tire manufacture as a mold release agent , in drilling mud , and in various cosmetics for its luster. Silicate minerals#Phyllosilicates Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust . In mineralogy , silica (silicon dioxide, SiO 2 )

966-429: 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

1035-401: Is 09.D – examples include: Phyllosilicates (from Greek φύλλον phýllon 'leaf'), or sheet silicates, form parallel sheets of silicate tetrahedra with Si 2 O 5 or a 2:5 ratio. The Nickel–Strunz classification is 09.E. All phyllosilicate minerals are hydrated , with either water or hydroxyl groups attached. Examples include: Tectosilicates, or "framework silicates," have

1104-438: 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,

1173-439: Is a simplification. Balancing the charges of the silicate anions are metal cations, M . Typical cations are Mg , Fe , and Na . The Si-O-M linkage between the silicates and the metals are strong, polar-covalent bonds. Silicate anions ([SiO 2+ n ] ) are invariably colorless, or when crushed to a fine powder, white. The colors of silicate minerals arise from the metal component, commonly iron. In most silicate minerals, silicon

1242-446: 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

1311-507: 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

1380-411: 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

1449-399: Is almost always much darker in color than muscovite. Paragonite can be difficult to distinguish from muscovite but is much less common, though it is likely mistaken for muscovite often enough that it may be more common that is generally appreciated. Muscovite mica from Brazil is red due to manganese(3+). Like all mica minerals, muscovite is a phyllosilicate (sheet silicate) mineral with

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1518-444: Is called an apical oxygen anion. There are three silicon cations for each aluminium cation but the arrangement of aluminium and silicon cations is largely disordered. The middle octahedral ( O ) sheet consists of aluminium cations that are each surrounded by six oxygen or hydroxide anions forming an octahedron, with the octahedrons sharing anions to form a hexagonal sheet similar to the tetrahedral sheets. The apical oxygen anions of

1587-448: Is common. Nesosilicates (from Greek νῆσος nēsos 'island'), or orthosilicates, have the orthosilicate ion , present as isolated (insular) [SiO 4 ] tetrahedra connected only by interstitial cations . The Nickel–Strunz classification is 09.A –examples include: Sorosilicates (from Greek σωρός sōros 'heap, mound') have isolated pyrosilicate anions Si 2 O 7 , consisting of double tetrahedra with

1656-407: 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

1725-576: Is in demand for the manufacture of fireproofing and insulating materials and to some extent as a lubricant . The name muscovite comes from Muscovy-glass , a name given to the mineral in Elizabethan England due to its use in medieval Russia ( Muscovy ) as a cheaper alternative to glass in windows. This usage became widely known in England during the sixteenth century with its first mention appearing in letters by George Turberville ,

1794-415: 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

1863-406: 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

1932-502: 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

2001-409: Is tetrahedral, being surrounded by four oxides. The coordination number of the oxides is variable except when it bridges two silicon centers, in which case the oxide has a coordination number of two. Some silicon centers may be replaced by atoms of other elements, still bound to the four corner oxygen corners. If the substituted atom is not normally tetravalent, it usually contributes extra charge to

2070-413: Is the most common mica , found in granites , pegmatites , gneisses , and schists , and as a contact metamorphic rock or as a secondary mineral resulting from the alteration of topaz , feldspar , kyanite , etc. It is characteristic of peraluminous rock , in which the content of aluminum is relatively high. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite

2139-539: Is usually considered a silicate mineral rather than an oxide mineral . Silica is found in nature as the mineral quartz , and its polymorphs . On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working the crust for billions of years. These processes include partial melting , crystallization , fractionation , metamorphism , weathering , and diagenesis . Living organisms also contribute to this geologic cycle . For example,

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2208-417: 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

2277-471: 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

2346-568: 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 ,

2415-399: 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

2484-445: 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

2553-521: 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

2622-401: The anion [AlSi 3 O 8 ] n , whose charge is neutralized by the potassium cations K . In mineralogy , silicate minerals are classified into seven major groups according to the structure of their silicate anion: Tectosilicates can only have additional cations if some of the silicon is replaced by an atom of lower valence such as aluminum. Al for Si substitution

2691-408: The anion, which then requires extra cations . For example, in the mineral orthoclase [KAlSi 3 O 8 ] n , the anion is a tridimensional network of tetrahedra in which all oxygen corners are shared. If all tetrahedra had silicon centers, the anion would be just neutral silica [SiO 2 ] n . Replacement of one in every four silicon atoms by an aluminum atom results in

2760-526: 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,

2829-445: 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

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2898-400: 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

2967-585: The formula (Si 2 x O 5 x ) or a 2:5 ratio. The Nickel–Strunz classification is 09.C. Possible ring sizes include: Some example minerals are: The ring in axinite contains two B and four Si tetrahedra and is highly distorted compared to the other 6-member ring cyclosilicates. Inosilicates (from Greek ἴς is [genitive: ἰνός inos ] 'fibre'), or chain silicates, have interlocking chains of silicate tetrahedra with either SiO 3 , 1:3 ratio, for single chains or Si 4 O 11 , 4:11 ratio, for double chains. The Nickel–Strunz classification

3036-544: 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

3105-534: 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

3174-431: 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

3243-512: 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

3312-421: 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

3381-488: 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

3450-475: 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

3519-402: 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 the equal charge constraint. The pH of

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3588-413: The hydroxide. Muscovite in which the mole fraction of silicon is greater than aluminium, and magnesium or iron replaces some of the aluminium to maintain charge balance, is called phengite . Muscovite can be cleaved into very thin transparent sheets that can substitute for glass, particularly for high-temperature applications such as industrial furnace or oven windows. It is also used in the manufacture of

3657-473: 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

3726-407: 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

3795-434: 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

3864-437: The octahedral sheet; fluorine or chlorine can substitute for hydroxide; and the ratio of aluminium to silicon in the tetrahedral sheets can change to maintain charge balance where necessary (as when magnesium cations, with a charge of +2, substitute for aluminium ions, with a charge of +3). Up to 10% of the potassium may be replaced by sodium, and up to 20% of the hydroxide by fluorine. Chlorine rarely replaces more than 1% of

3933-403: The outer T sheets face inwards and are shared by the octahedral sheet, binding the sheets firmly together. The relatively strong binding between oxygen anions and aluminium and silicon cations within a layer, compared with the weaker binding of potassium cations between layers, gives muscovite its perfect basal cleavage. In muscovite, alternate layers are slightly offset from each other, so that

4002-442: 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

4071-480: 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

4140-402: 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

4209-579: The secretary of England's ambassador to the Russian tsar Ivan the Terrible , in 1568. Micas are distinguished from other minerals by their pseudohexagonal crystal shape and their perfect cleavage, which allows the crystals to be pulled apart into very thin elastic sheets. Pyrophyllite , and talc are softer than micas and have a greasy feel, while chlorite is green in color and its cleavage sheets are inelastic. The other common mica mineral, biotite ,

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4278-400: 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 ]

4347-550: 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

4416-499: 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,

4485-482: 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

4554-475: The structure repeats every two layers. This is called the 1 M polytype of the general mica structure. The formula for muscovite is typically given as KAl 2 (AlSi 3 O 10 )(OH) 2 , but it is common for small amounts of other elements to substitute for the main constituents. Alkali metals such as sodium , rubidium , and caesium substitute for potassium; magnesium , iron , lithium , chromium , titanium , or vanadium can substitute for aluminium in

4623-429: 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 ]

4692-653: 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

4761-485: 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,

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