Silicon dioxide glass from

Some metals that are chemically combined with oxygen (metal oxides) also dissolve in sodium hydroxide. For example, aluminum ore (known as bauxite) is treated with sodium hydroxide to isolate pure aluminum oxide, from which pure aluminum is obtained. Sand (silicon dioxide) will also dissolve in sodium hydroxide to form a chemical known as sodium silicate or water glass. 

The composition of the particles is related to that of the source rocks. Quartz sand [composed of silica (silicon dioxide)], which makes up the most common variety of silica sand, is derived from quartz rocks. Pure quartz is usually almost free of impurities and therefore almost colorless (white). The coloration of some silica sand is due to chemical impurities within the structure of the quartz. The common buff, brown, or gray, for example, is caused by small amounts of metallic oxides iron oxide makes the sand buff or brown, whereas manganese dioxide makes it gray. Other minerals that often also occur as sand are calcite, feldspar and obsidian Calcite (composed of calcium carbonate), is generally derived from weathered limestone or broken shells or coral feldspar is an igneous rock of complex composition, and obsidian is a natural glass derived from the lava erupting from volcanoes see Chapter 2. 

The shatterproof glass used in impact-resistant windows is actually not a glass material derived from silicon dioxide. Instead, shatterproof glass is a thermoset plastic or thermoplastic, i.e., a pliable material that is even easier to mold when hot. Shatterproof windows are made using a specific thermoset material known as polycarbonate of bisphenol A (or bisphenol A polycarbonate). This clear,... 

Pyrex glass contains about 80% of silicon dioxide, about 5% of alkalies, and has a low expansion coefficient. Ware made from it has a high thermal stability. The softening point of this glass is about 620 °C. 

In 1992, R.M. Laine (University of Michigan, Ann Arbor) announced the development of a process that transforms sand and other forms of silica into reactive silicates that can be used to synthesize unusual silicon-based chemicals, polymers, glasses, and ceramics. The Lame procedure produces pentacoordinate silicates directly from low-cost raw materials—silicon dioxide,ethylene glycol, and an alkali base. The mixture is approximately a 60 1 ratio of silica gel, fused silica (or sand) to metal hydroxide and ethylene... 

A source of error in chemical analyses of montmorillonites (and in other clays) that is not commonly checked is the presence of amorphous material, particularly Si and Al. Table XXXII lists structural formulas given by Osthaus (1955) for montmorillonites which were purified by size fraction and by extraction with 0.5 N NaOH to remove amorphous Si and Al. In six analyses dissolved silica ranged from 3.6 to 8.4% and alumina from 0.6 to 2.25%. Amorphous silicon dioxide should be expected in most montmorillonites derived from volcanic material. The source glass has more Si than is required for the 2 1 layer and the excess must be leached from the glass. Much of the Si is deposited in the sediments underlying the bentonite bed in the form of chert but it is to be expected that the extraction would not be complete and a portion of the colloidal Si would remain in the bentonite bed. 

Sodium silicate is stored and shipped as a liquid, but when exposed to air, it will turn into a hard, glass-like material. In reality, it is a glass in a totally anhydrous form the sodium hydroxide content is 34% by weight, and the remaining 66% is silicon dioxide. These proportions are theoretical, however, as an anhydrous sodium silicate is not really possible because it would always be absorbing water from the air. 

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