Silicon dioxide tridymite

Silicon dioxide (tridymite) respirable size Tridymite 15468-32-3... 

Thenardite, see Sodium sulfate Thionyl, see Sulflnyl Thorianite, see Thorium dioxide Topaz, see Aluminum hexafluorosilicate Tridymite, see Silicon dioxide Troilite, see Iron(II) sulflde... 

The arrangement of oxygen atoms in ice I is isomorphous with the wurtzite form of zinc sulphide, and also with the silicon atoms in the tridymite form of silicon dioxide. Hence, ice I is sometimes referred to as the wurtzite or tridymite form of ice (Eisenberg Kauzmann, 1969). 

In the different forms of silicon dioxide (quartz, tridymite, cristobalite, etc.), each silicon is surrounded by four oxygen atoms, each oxygen atom of a tetrahedral group Si04 being shared by two such groups. 

Silicon dioxide (sihca), SiO. , occurs in nature in three different crystal forms, as the minerals quartz (hexagonal), cristohalite (cubic), and tridymite (hexagonal). Quartz is the most widespread of these minerals it occurs in many deposits as well-formed hexagonal crystals, and also as a clrystalline constituent of many rocks, such as granite. It is a hard, colorless substance, with hardness 7 on the Mohs scale. Its crystals may be identified as right-handed or left-handed, by their face development (Fig. 31-1), and also by the direction in which they rotate the plane of polarization of polarized light. 

In contrast to the discrete molecules of carbon dioxide, silicon dioxide forms condensed, three-dimensional systems of indefinite extension which are high-melting solids. Silica has three forms, quartz, tridymite and cristobalite, each of which has a low-temperature (a) and a high-temperature (/3) modification. 

Silicon Dioxide. Silica silicic anhydride. 02Si mol wt 60.09. O 53.25%, Si 46.75%. Si02. Occurs in nature as agate, amethyst, chalcedony, cristobalite, flint, quartz, sand, tridymite. Reviews Several authors in Kirk-Othmer Encyclopedia of Chemical Technology vol. 18 (Interscience. New York, 2nd ed., 1969) pp 46.111 Rochow in Comprehensive Inorganic Chemistry vol. 1, I. C. Bailar, Jr. et al Eds. (Pergamon Press, Oxford, 1973) pp 1388-1402. 

Although methods are available for synthesizing silicon dioxide, there is no practical reason for doing so. The abundant quantities of silicon dioxide found in the earth s crust are sufficient to satisfy all industrial needs. Among the minerals and earths that contain silicon dioxide in an uncombined form are quartz, flint, diatomite, stishovite, agate, amethyst, chalcedony, cristobalite, and tridymite. 

Definition Oaurs in nature as agate, amethyst, chalcedony, cristobalite, flinL quartz, sand, tridymite, diatomite. The designation silica (silicon dioxide) ind. ctysL, amoqthous forms which are hydrated or hydroxy-... 

Silicon dioxide cristobalite (regular) tridymite (hexagonal) quartz (trigonal)... 

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