Кварц

Описание

Quartz is a colorless solid that exists in numerous crystalline forms. Oxygen and silicon are the two most common elements in the earth's crust, and Quartz is the principal component of sand. Quartz is used biologically, most notably by phytoplankton diatoms and the zooplankton radiolarians in their shells. Quartz, SiO₂, should not be confused with Quartz or silicones. Quartz contain the basic tetrahedral unit SiO₄4-bonded to metal ions such as aluminum, iron, sodium, magnesium, calcium, and potassium to form numerous Quartz minerals. Silicones are synthetic polymers made of monomers with at least two silicon atoms combined with an organic group and generally containing oxygen.

Химические свойства

granular abrasive solid of varied colour, depending upon other

Вхождение

Quartz is the oxide of the nonmetallic element silicon, is the commonest of minerals, and appears in a greater number of forms than any other. Its formula is SiO₂. Quartz commonly occurs in prismatic hexagonal crystals terminated by a pyramid. This pyramid is due to the equal development of two rhombohedrons, and may be observed in cases where one rhombohedron predominates. Cleavage is not observed; the fracture is typically conchoidal; hardness is 7; specific gravity, 2.65; luster, vitreous to greasy or dull; colorless to white, pink, purple, yellow, blue, green, smoky brown to nearly black; transparent to opaque.

Характеристики

Quartz can exist in either a crystalline or noncrystalline form. In Quartz, SiO₂ exists in the natural crystalline state and possesses long-range order, with the silicon atom covalently bonded to oxygen atoms in a tetrahedral arrangement in a regular repeating pattern. Glass is an example of noncrystalline Quartz. Although natural glasses exist, Quartz glasses are produced when Quartz is heated to an elevated temperature and then rapidly cooled. The rapid cooling does not allow the SiO₂ to form a regular crystalline structure with long-range order. The result is a solid that behaves like a viscous liquid when heated. Glass is sometimes called a solid solution and fl ows at a very slow rate. This can sometimes be seen in old window glass where the bottom is slightly thicker than the top. The actual structures form a three-dimensional tetrahedral pattern. Quartz is sold as sand and its main uses are for glass; ceramics; foundry sand, a source of silicon in the chemical industry; as a filtration media; a filler/extender; an abrasive; and as an adsorbent.

Использование

Sand, white silica has been employed as a solid sample to evaluate the pore-volume variations during fluid-rock interaction experiments.

Определение

A purple form of the mineral quartz (silicon(IV) oxide, SiO₂) used as a semiprecious gemstone. The color comes from impurities such as oxides of iron.

Реакции

SiO2 shows strong absorption at 8.5 mm, 9.2 mm, and 12.5 mm (refer to the Silica) and SiO at 10.4 m. Thin films of SiO2 are fabricated by oxidizing the SiO in air after deposition of SiO by vacuum evaporation.

Общее описание

The product is sand, white quartz (SiO₂). Its reaction with alkaline NaNO₃ solutions containing dissolved Al at 89°C has been investigated.

Опасность

Avoid inhalation of fine particles.

Угроза здоровью

Exposure to Quartz can result in the disease called silicosis. Silicosis is a disabling, nonreversible, and sometimes fatal lung disease caused by overexposure to respirable crystalline Quartz. In silicosis, Quartz particles enter the lung where they become trapped, producing areas of swelling. The swelling results in nodules that become progressively larger as the condition worsens. Silicosis is defined at several levels of severity: chronic silicosis, accelerated silicosis, and acute silicosis. Chronic silicosis results from long-term (20 years) exposure to low concentrations of Quartz, whereas acute silicosis is the result of a short-term exposure (a year or less) to high concentrations. Symptoms may not be obvious in cases of chronic silicosis and x-ray screening is recommended for at-risk groups. These include sand-blasters, miners, laborers who regularly saw, drill, and jack-hammer concrete, and general construction such as tunnel drilling. In advanced stages of silicosis, individuals have difficulty breathing, especially when active.

Промышленное использование

Crushed and graded quartz is used as the abrasive in flint sandpapers. Almost any deposit of massive white quartz is suitable. Being the cheapest of all the abrasive-coated paper, this product is still sold in fair amounts, mainly in hardware stores and by small jobbers. It is made only in the form of paper, not as cloth. True chalk flint from England and France is used extensively for this purpose in Europe; it has better cutting qualities and longer life than ordinary quartz. Crushed and ground sand, sandstone, powdered quartz, and silt are sometimes used in hand soaps, scouring compounds, and harsher metal polishes.

Профиль безопасности

Confirmed carcinogen with experimental carcinogenic, tumorigenic, and neoplastigenic data. Experimental poison by intratracheal and intravenous routes. An inhalation hazard. Human systemic effects by inhalation: cough, dyspnea, liver effects. Incompatible with OF2, vinyl acetate. See also other silica entries

Возможный контакт

Cristobalite is used in the manufacture of water glass, refractories, abrasives, ceramics and enamels. Quartz is used as a mineral, natural or synthetic fiber. Tridymite is used as a filtering and insulating media and as a refractory material for furnace linings. Workers are potentially exposed to crystalline silica in such industries as granite quarrying and cutting, foundry operations; metal, coal, dentistry, painting, and nonmetallic mining; and manufacture of clay and glass products.

Канцерогенность

Quartz was not mutagenic in bacterial assays; both positive and negative results have been reported in a wide variety of in vivo and in vitro genotoxic assays.

Несовместимости

Violent reactions with powerful oxidizers: fluorine, chlorine trifluoride; manganese trioxide; oxygen difluoride, hydrogen peroxide, etc.; acetylene; ammonia.

Утилизация отходов

Sanitary landfill