Orthosilicates s. Silicates

Orthophosphoric acid esters, alkylation with - 22, 775 Orthosilicates s. Silicates Osmic acid s. Osmium tetroxide Osmium tetroxide OCv >CC Oxa... s. a. 0-Heterocyclics Oxacyclimmonium salts, 2-hydroxy- 22, 990, 3,5-Oxadiazines, 6-oxo-... 

Different minerals contain different metal cations to balance the -4 charge on the orthosilicate ion. Examples Include calcium silicate (Ca2 Si04), an important ingredient in cement, and zircon (ZrSi04), which is often sold as artificial diamond. One of the most prevalent minerals in the Earth s mantle is olivine, Af2(Si04), in which M is one or two of the abundant metal cations, Fe -, Mg -, and Mn +. 

Kieflfer S. W. (1980). Thermodynamics and lattice vibrations of minerals, 4 Application to chain and sheet silicates and orthosilicates. Rev. Geophys. Space Phys., 18 862-886. 

We often ask the question Why does such and such a compound exist but more rarely do we ask the question Why does such and such a compound not exist , yet the answer to the second question may be more revealing than the answer to the first. A number of years ago, Dent-Glasser (1979) published a paper entitled Non-existent silicates in which she noted that there were many stoichiometrically allowed silicate structures that had never been observed. In particular she pointed out that the alkali metals rarely formed orthosilicates such as Na4Si04, and transition metals rarely formed highly condensed silicates such as NiSi40g. Dent-Glasser s list of known silicates is shown in Fig. 4.6... 

The US military specifications embodying the requirements for Na silicate are presented in 0-S-604 C (1) for Sodium Metasilicate, Technical (Ref 12a), P-S-651E (1) for Sodium Orthosilicate, Technical (Ref 12b) and O-S-605D for Sodium Silicate Solution (Ref 6a)... 

The outermost layer of our planet, the crust, contains the accessible mineral wealth of the planet. The eight most abundant elements in the crust (Table 1) make up 98.5% of the mass of the crust [10], The most common metal, silicon, is never found in its elemental form in nature. Instead, silicon is combined in silicate minerals, which make up more than 90% of the mass of the Earth s crust [11], Depending on the composition and formation conditions, silicate minerals have structures that range from individual clusters (orthosilicates) to three-dimensional networks (tecto-silicates) [11], These minerals can be contained in relatively pure single mineral deposits or, more commonly, in rocks such as granite that are made up of one or more mineral species. 

If a highly alkaline sodium silicate waste is classified as a hazardous waste under RCRA, it is also a hazardous substance under the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA or Superfund Act), The law s reporting requirements would apply to any release into the environment. This is also true for the previously mentioned sodium orthosilicate products which are EPA hazardous substances, since they are physical mixtures containing sodium hydroxide. For sodium hydroxide the reportable quantity remains... 

Silicon dioxide and other compounds that contain silicon and oxygen comprise over 90% of Earth s crust. Silicates are compounds in which a silicon atom is surrounded in a tetrahedral fashion by four oxygens, as shown in Figure 22.51 . In silicates, silicon is found in its most common oxidation state, +A. The simple Si04 ion, which is known as the orthosilicate ion, is found in very few silicate minerals. We can view the silicate tetrahedra, however, as "building blocks" that are used to build mineral structures. The individual tetrahedra are linked together by a common oxygen atom that serves as a vertex of both tetrahedra. 

Yuh S.-K., Bescher E.P., Babonneau F., Mackenzie J.D. Rare-earth doped, low hydroxyl organically modified silicates. Mater. Res. Soc. Symp. Proc. 1994 346 803-808 Zha C., Atkins G.R., Masters A.F. A spectroscopic study of an anhydrous tetraethyl orthosilicate-boric acid-ethanol system. J. Sol-Gel Sci. Tech. 1998 13 103-107 Zha C., Atkins G.R., Masters A.F. Preparation and spectroscopy of anhydrous borosilicate sols and their application to thin films. J. Non-Cryst. Sohds 1998 242 63-67. 

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