Silicate stability

Figure 4. Silicate stability. KF, KM, G, K, and Q are K+-feld-spar, K+-mica, gibbsite, kaolinite, and amorphous silica, respectively. M and AB are montmorillonite and albite. W, S, FW, and SW represent areas of winter lake data, summer lake data, extracted fresh water sediments, and extracted sea water sediments, respectively...

Figure 11.10 (a) Rate of syneresis for sodium silicate stabilized with glyoxal. (From Reference 19.) (b) Syneresis rates of silicate with different catalysts. (From Reference 18.)... 

G. Wa5me Clough, William Kuck and Gyimah Kasali, Silicate Stabilized Sands, Journal of the Geotechnical Engineering Division, January, 1979, ASCE, Reston, VA. 

A neutral sol of 3 per cent silica prepared in this way is liable to set to a thin gel on standing, since there is not enough electrolyte present to stabilize it. A very little sodium silicate stabilizes the sol so that it can be concentrated to 20 per cent silica content, and such a sol is used in large quantities in textile dressing. 

Figure 2.62 Silicate stability fields in water vs. Ca +/2H ratio and H SiO content at 25 C and pressure 0.1 MPa (Shvartsev, 1998). Symbols describe ground water composition in West Africa 1. Guinea 2. Korhogo 3. Cote d Ivoire 4. North Nigeria 5. Chad 6. Senegal 7. Line separating kaolinite and gibbsite, after Helgeson et al.

The modification that is most reactive and thus the most important in cement chemistry is -028, which is thermodynamically unstable at any temperature. Upon cooling it tends to transform to urrless doped with stabiUzing ions. In its doped form P-C2S, also called belite, is a regular corrstituent of a variety of inorganic binders, including Portland cement High-temperature modifications of dicaldum silicate, stabilized by different dopants, exhibit variable reactivities, and may be found in some special cements. 

Alkalinity sodium hydroxide, silicate Stabilize bleach 0.25-5... 

Silicate Esters. Silicate esters, Si(OR)4 where R is an aryl or alkyl group, have excellent thermal stability, and using proper inhibitors, show... 

For waterproofing, sodium silicate concentrations below 30% are adequate concentrations between 35 and 70% are used for strength improvement. Grouts having 35 vol % or higher silicate resist deterioration on freeze—thaw or wet—dry cycles. Water permeability of sands can be reduced from 10 to 10 cm/s. Unconfined compressive strengths of stabilized sand can vary from 103 to 4130 kPa (15—600 psi) the normal range is between 690 and 1380 kPa. 

Pigment Systems. Most of the crystals used for ceramic pigments are complex oxides, owing to the great stability of oxides in molten silicate glasses. Table 3 fists these materials. The one significant exception to the use of oxides is the family of cadmium sulfoselenide red pigments. This family is used because the colors obtained caimot be obtained in oxide systems thus it is necessary to sustain the difficulties of a nonoxide system. 

Chemical Reactivity - Reactivity with Water Reacts vigorously to form corrosive and toxic hydrofluoric acid Reactivity with Common Materials In the presence of moisture, is corrosive to glass, other siliceous materials, and most metals Stability During Transport Stable Neutralizing Agents for Acids and Caustics Flush with water, rinse with sodium bicarbonate or lime solution Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

C) for cast iron and up to 140 °F for marstenitic SS (60 °C). It is widely used where silicates are present with the iron oxides. Typically, 5 to 7.5% HC1 is employed. The ammonium bifluoride normally is present at 0.5%, but it may be increased to a maximum of 1.5% for a boiler that has not been cleaned for many years. The presence of hydrofluoric acid (HF), which is formed by the reaction of ammonium bifluoride with HC1 (see equation), tends to increase the rate of iron oxide dissolution and reduce the corrosion rate of exposed steel, when compared to using HC1 alone. This is due to the stability of the hexafluoroferric ion (FeFg3 ), which prevents the ferric ion from corroding exposed steel. 

The 3 percent hydrogen peroxide you get at the drugstore is often protected from decomposing by the addition of sodium silicate, magnesium sulfate, or tin compounds. These stabilizers lock up the iron, copper, and other transition metals that can act as catalysts. 

Ceramic materials are typically noncrystalline inorganic oxides prepared by heat-treatment of a powder and have a network structure. They include many silicate minerals, such as quartz (silicon dioxide, which has the empirical formula SiO,), and high-temperature superconductors (Box 5.2). Ceramic materials have great strength and stability, because covalent bonds must be broken to cause any deformation in the crystal. As a result, ceramic materials under physical stress tend to shatter rather than bend. Section 14.22 contains further information on the properties of ceramic materials. 

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