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Phosphorus Sesquisulfide
Phosphorus sesquisulfide is the inorganic compound with the formula . It was developed by Henri Sevene and Emile David Cahen in 1898 as part of their invention of friction matches that did not pose the health hazards of white phosphorus. This yellow solid is one of two commercially produced phosphorus sulfides. It is a component of "strike anywhere" matches. Depending on purity, samples can appear yellow-green to grey. The compound was discovered by G. Lemoine and first produced safely in commercial quantities in 1898 by Albright and Wilson. It dissolves in an equal weight of carbon disulfide (), and in a 1:50 weight ratio of benzene. Unlike some other phosphorus sulfides, is slow to hydrolyze and has a well-defined melting point. Structure and synthesis The molecule has C3v symmetry. It is a derivative of the tetrahedral () unit from insertion of sulfur into three P-P bonds. The P-S and P-P distances are 2.090 and 2.235 Å, respectively. and adopt the same structures. These ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base (''a'' by ''b'') and height (''c''), such that ''a'', ''b'', and ''c'' are distinct. All three bases intersect at 90° angles, so the three lattice vectors remain mutually orthogonal. Bravais lattices There are four orthorhombic Bravais lattices: primitive orthorhombic, base-centered orthorhombic, body-centered orthorhombic, and face-centered orthorhombic. For the base-centered orthorhombic lattice, the primitive cell has the shape of a right rhombic prism;See , row oC, column Primitive, where the cell parameters are given as a1 = a2, α = β = 90° it can be constructed because the two-dimensional centered rectangular base layer can also be described with primitive rhombic axes. Note that the length a of the primit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Albright And Wilson
Albright and Wilson was founded in 1856 as a United Kingdom manufacturer of potassium chlorate and white phosphorus for the match industry. For much of its first 100 years of existence, phosphorus-derived chemicals formed the majority of its products. It was set up as a partnership between two Quakers, Arthur Albright, and John Edward Wilson. It became a private limited company, Albright & Wilson Ltd, in 1892; and it remained a double family-owned firm, for nearly 100 years, until 5 March 1948, when it became a public company.Threlfall (1951). Chapter XIV: ''The Public Company.'' Albright and Wilson expanded considerably into silicones, detergents, food additives, metal finishing chemicals, strontium based chemicals and chromium based chemicals. It was the second largest chemical manufacturer in the United Kingdom; although it was always very much smaller than ICI. In 1971 Tenneco bought a part of Albright and Wilson's share holdings; and in 1978 obtained full ownership. In the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contact Dermatitis
Contact dermatitis is a type of acute or chronic inflammation of the skin caused by exposure to chemical or physical agents. Symptoms of contact dermatitis can include itchy or dry skin, a red rash, bumps, blisters, or swelling. These rashes are not contagious or life-threatening, but can be very uncomfortable. Contact dermatitis results from either exposure to allergens (allergic contact dermatitis), or irritants (irritant contact dermatitis). Allergic contact dermatitis involves a delayed type of hypersensitivity and previous exposure to an allergen to produce a reaction. Irritant contact dermatitis is the most common type and represents 80% of all cases. It is caused by prolonged exposure to irritants, leading to direct injury of the epidermal cells of the skin, which activates an immune response, resulting in an inflammatory cutaneous reaction. Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight. Diagnosis of allergic contact dermatitis can o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Match
A match is a tool for starting a fire. Typically, matches are made of small wooden sticks or stiff paper. One end is coated with a material that can be ignited by friction generated by striking the match against a suitable surface. Wooden matches are packaged in matchboxes, and paper matches are partially cut into rows and stapled into matchbooks. The coated end of a match, known as the match "head", consists of a bead of active ingredients and binder (material), binder, often colored for easier inspection. There are two main types of matches: safety matches, which can be struck only against a specially prepared surface, and strike-anywhere matches, for which any suitably frictional surface can be used. Because of the substance used to coat each match, this makes them non-biodegradable. Etymology Historically, the term ''match'' referred to lengths of rope, cord (later cambric) impregnated with chemicals, and allowed to burn continuously. These were used to light fires and fir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Chlorate
Potassium chlorate is a compound containing potassium, chlorine and oxygen, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. After sodium chlorate, it is the second most common chlorate in industrial use. It is a strong oxidizing agent and its most important application is in safety matches. In other applications it is mostly obsolete and has been replaced by safer alternatives in recent decades. It has been used * in fireworks, propellants and explosives, * to prepare oxygen, both in the lab and in chemical oxygen generators, * as a disinfectant, for example in medical mouthwashes, * in agriculture as an herbicide. Production On the industrial scale, potassium chlorate is produced by the salt metathesis reaction of sodium chlorate and potassium chloride: : NaClO3 + KCl → NaCl + KClO3 The reaction is driven by the low solubility of potassium chlorate in water. The equilibrium of the reaction is shifted to the right hand side by the continuo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphorus Pentasulfide
Phosphorus pentasulfide is the inorganic compound with the formula (monomer) or (dimer). This yellow solid is the one of two phosphorus sulfides of commercial value. Samples often appear greenish-gray due to impurities. It is soluble in carbon disulfide but reacts with many other solvents such as alcohols, DMSO, and DMF. Structure and synthesis Its tetrahedral molecular structure is similar to that of adamantane and almost identical to the structure of phosphorus pentoxide. Phosphorus pentasulfide is obtained by the reaction of liquid white phosphorus () with sulfur above 300 °C. The first synthesis of by Berzelius in 1843 was by this method. Alternatively, can be formed by reacting elemental sulfur or pyrite, , with ferrophosphorus, a crude form of (a byproduct of white phosphorus () production from phosphate rock): : : Applications Approximately 150,000 tons of are produced annually. The compound is mainly converted to other derivatives for use as lubrication ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphorus Selenide
Phosphorus selenides are a relatively obscure group of compounds. There have been some studies of the phosphorus - selenium phase diagram and the glassy amorphous phases are reported. The compounds that have been reported are shown below. While some of phosphorus selenides are similar to their sulfide analogues, there are some new forms, molecular and the polymeric ''catena''-. There is also some doubt about the existence of molecular . Crystallographically confirmed compounds Molecular has a norbornane like structure with two phosphorus atoms with oxidation state +3 bridged by two diselenide units (, analogous to disulfide) and one selenide unit (). It was isolated by solvent ( ) extraction from a amorphous phase made from the elements. has been characterised crystallographically and has the same structure as the low temperature form of . It can be prepared from the elements. One preparation is to extract and recrystallise using tetralin. The molecule has the same struct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Symmetry
Molecular symmetry in chemistry describes the symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explain many of a molecule's chemical properties, such as whether or not it has a dipole moment, as well as its allowed spectroscopic transitions. To do this it is necessary to use group theory. This involves classifying the states of the molecule using the irreducible representations from the character table of the symmetry group of the molecule. Symmetry is useful in the study of molecular orbitals, with applications to the Hückel method, to ligand field theory, and to the Woodward-Hoffmann rules. Many university level textbooks on physical chemistry, quantum chemistry, spectroscopy and inorganic chemistry discuss symmetry. Another framework on a larger scale is the use of crystal systems to describe crystallographic symmetry in bulk materia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline. It is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although benzene is a major industrial chemical, it finds limited use in consumer items because of its toxicity. History Discovery The word "''benzene''" derives from "''gum benzoin''" (benzoin res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Disulfide
Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non-polar solvent. It has an "ether-like" odor, but commercial samples are typically contaminated with foul-smelling impurities.. It is of comparable toxicity to carbon monoxide. History In 1796, the German chemist Wilhelm August Lampadius (1772–1842) first prepared carbon disulfide by heating pyrite with moist charcoal. He called it "liquid sulfur" (''flüssig Schwefel''). The composition of carbon disulfide was finally determined in 1813 by the team of the Swedish chemist Jöns Jacob Berzelius (1779–1848) and the Swiss-British chemist Alexander Marcet (1770–1822). Their analysis was consistent with an empirical formula of CS2. Occurrence, manufacture, properties Small amounts of carbon disulfide are released by volcanic eruptio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commerce
Commerce is the large-scale organized system of activities, functions, procedures and institutions directly and indirectly related to the exchange (buying and selling) of goods and services among two or more parties within local, regional, national or international economies. More specifically, commerce is not business, but rather the part of business which facilitates the movement and distribution of finished or unfinished but valuable goods and services from the producers to the end consumers on a large scale, as opposed to the sourcing of raw materials and manufacturing of those goods. Commerce is subtly different from trade as well, which is the final transaction, exchange or transfer of finished goods and services between a seller and an end consumer. Commerce not only includes trade as defined above, but also a series of transactions that happen between the producer and the seller with the help of the auxiliary services and means which facilitate such trade. These auxiliary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schönflies Notation
The Schoenflies (or Schönflies) notation, named after the German mathematician Arthur Moritz Schoenflies, is a notation primarily used to specify point groups in three dimensions. Because a point group alone is completely adequate to describe the symmetry of a molecule, the notation is often sufficient and commonly used for spectroscopy. However, in crystallography, there is additional translational symmetry, and point groups are not enough to describe the full symmetry of crystals, so the full space group is usually used instead. The naming of full space groups usually follows another common convention, the Hermann–Mauguin notation, also known as the international notation. Although Schoenflies notation without superscripts is a pure point group notation, optionally, superscripts can be added to further specify individual space groups. However, for space groups, the connection to the underlying symmetry elements is much more clear in Hermann–Mauguin notation, so the latter not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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