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Protactinium(V) Fluoride
Protactinium(V) fluoride is a fluoride of protactinium with the chemical formula PaF5. Preparation Protactinium(V) fluoride can be obtained by reacting protactinium(V) oxide with bromine trifluoride or bromine pentafluoride at 600 °C: :3 Pa2O5 + 10 BrF3 (6 BrF5) -> 6 PaF5 + 5 Br2 (3 Br2 ) + 7.5 O2 It can also be obtained by reacting protactinium(V) chloride or protactinium(IV) fluoride with fluorine gas at 700 °C: :2 PaF4 + F2 -> 2 PaF5 The hydrate form of protactinium(V) fluoride can be formed by the reaction of protactinium(V) oxide and hydrofluoric acid in an aqueous solution: :Pa2 O5 + 10 HF -> 2 PaF5 . 2 H2O + 6 H2O It can also be decomposed from fluorine-containing protactinium complexes. Properties Protactinium(V) fluoride is a white, volatile, extremely hygroscopic solid that is partially soluble in water and soluble in hydrofluoric acid. It has a tetragonal crystal structure of the β- uranium pentafluoride type with the space group ''I''42''d'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent). It is vital for all known forms of life, despite not providing food, energy or organic micronutrients. Its chemical formula, H2O, indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. "Water" is also the name of the liquid state of H2O at standard temperature and pressure. A number of natural states of water exist. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds consist of suspended droplets of water and ice, its solid state. When finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is steam or water vapor. Water co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hygroscopic
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance's molecules, adsorbing substances can become physically changed, e.g., changing in volume, boiling point, viscosity or some other physical characteristic or property of the substance. For example, a finely dispersed hygroscopic powder, such as a salt, may become clumpy over time due to collection of moisture from the surrounding environment. ''Deliquescent'' materials are sufficiently hygroscopic that they absorb so much water that they become liquid and form an aqueous solution. Etymology and pronunciation The word ''hygroscopy'' () uses combining forms of '' hygro-'' and '' -scopy''. Unlike any other ''-scopy'' word, it no longer refers to a viewing or imaging mode. It did begin that way, with the word ''hygroscope'' referring in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protactinium(V) Compounds
Protactinium (formerly protoactinium) is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray actinide metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds in which protactinium is usually present in the oxidation state +5, but it can also assume +4 and even +3 or +2 states. Concentrations of protactinium in the Earth's crust are typically a few parts per trillion, but may reach up to a few parts per million in some uraninite ore deposits. Because of its scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel. The element was first identified in 1913 by Kazimierz Fajans and Oswald Helmuth Göhring and named ''brevium'' because of the short half-life of the specific isotope studied, i.e. protactinium-234. A more stable isotope of protactinium, 231Pa, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Fluoride
Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock in the preparation of many important compounds including pharmaceuticals and polymers, e.g. polytetrafluoroethylene (PTFE). HF is widely used in the petrochemical industry as a component of superacids. Hydrogen fluoride boils at near room temperature, much higher than other hydrogen halides. Hydrogen fluoride is an extremely dangerous gas, forming corrosive and penetrating hydrofluoric acid upon contact with moisture. The gas can also cause blindness by rapid destruction of the corneas. History In 1771 Carl Wilhelm Scheele prepared the aqueous solution, hydrofluoric acid in large quantities, although hydrofluoric acid had been known in the glass industry before then. French chemist Edmond Frémy (1814–1894) is credited with discoveri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphorus Trifluoride
Phosphorus trifluoride (formula P F3), is a colorless and odorless gas. It is highly toxic and reacts slowly with water. Its main use is as a ligand in metal complexes. As a ligand, it parallels carbon monoxide in metal carbonyls, and indeed its toxicity is due to its binding with the iron in blood hemoglobin in a similar way to carbon monoxide. Physical properties Phosphorus trifluoride has an F−P−F bond angle of approximately 96.3°. Gaseous PF3 has a standard enthalpy of formation of −945 kJ/mol (−226 kcal/ mol). The phosphorus atom has a nuclear magnetic resonance chemical shift of 97 ppm (downfield of H3PO4). Properties Phosphorus trifluoride hydrolyzes especially at high pH, but it is less hydrolytically sensitive than phosphorus trichloride. It does not attack glass except at high temperatures, and anhydrous potassium hydroxide may be used to dry it with little loss. With hot metals, phosphides and fluorides are formed. With Lewis bases such a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrex
Pyrex (trademarked as ''PYREX'' and ''pyrex'') is a brand introduced by Corning Inc. in 1915 for a line of clear, low-thermal-expansion borosilicate glass used for laboratory glassware and kitchenware. It was later expanded to include kitchenware products made of soda-lime glass and other materials. In 1998, the kitchenware division of Corning Inc. responsible for the development of Pyrex spun off from its parent company as Corning Consumer Products Company, subsequently renamed Corelle Brands (and would later merge with Instant Brands). Corning Inc. no longer manufactures or markets consumer products, only industrial ones. Both trademarks, PYREX (all uppercase) and pyrex (all lowercase, introduced in 1975), were used interchangeably in the marketing of kitchenware products made of both borosilicate and soda lime glass, in addition to related accessories, for several decades. The latter trademark is now used for kitchenware sold in the United States, South America, and Asia. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at . Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz, several of which are classified as gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. Quartz is the mineral defining the val ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium Pentafluoride
Uranium pentafluoride is the inorganic compound with the chemical formula UF5. It is a pale yellow paramagnetic solid. The compound has attracted interest because it is related to uranium hexafluoride, which is widely used to produce uranium fuel. It crystallizes in two polymorphs, called α- and β-UF5. Synthesis and structure Uranium pentafluoride is an intermediate in the conversion of uranium tetrafluoride to volatile UF6: :2UF4 + F2 → 2UF5 :2UF5 + F2 → 2UF6 It can be produced by reduction of the hexafluoride with carbon monoxide at elevated temperatures. : 2UF6 + CO → 2UF5 + COF2 Other reducing agents have been examined. The α form is a linear coordination polymer consisting of chains of octahedral uranium centers in which one of the five fluoride anion forms a bridge to the next uranium atom. The structure is reminiscent of that for vanadium pentafluoride. In the β form, the uranium centers adopt a square antiprismatic structure. The β polymorp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns that repeat along the principal directions of Three-dimensional space (mathematics), three-dimensional space in matter. The smallest group of particles in the material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive Translation (geometry), translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice. The lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants, also called ''lattice parameters'' or ''cell parameters''. The symmetry properties of the crystal are described by the con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetragonal Crystal System
In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square base (''a'' by ''a'') and height (''c'', which is different from ''a''). Bravais lattices There are two tetragonal Bravais lattices: the primitive tetragonal and the body-centered tetragonal. The base-centered tetragonal lattice is equivalent to the primitive tetragonal lattice with a smaller unit cell, while the face-centered tetragonal lattice is equivalent to the body-centered tetragonal lattice with a smaller unit cell. Crystal classes The point groups that fall under this crystal system are listed below, followed by their representations in international notation, Schoenflies notation, orbifold notation, Coxeter notation and mineral examples.Hurlbut, Cornelius S.; Klein, Cornelis, 1985, ''Manual of Mineralogy'', 20th ed., pp. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solubility
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubility of a substance in a specific solvent is generally measured as the concentration of the solute in a saturated solution, one in which no more solute can be dissolved. At this point, the two substances are said to be at the solubility equilibrium. For some solutes and solvents, there may be no such limit, in which case the two substances are said to be " miscible in all proportions" (or just "miscible"). The solute can be a solid, a liquid, or a gas, while the solvent is usually solid or liquid. Both may be pure substances, or may themselves be solutions. Gases are always miscible in all proportions, except in very extreme situations,J. de Swaan Arons and G. A. M. Diepen (1966): "Gas—Gas Equilibria". ''Journal of Chemical Physics'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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