Silicate, sodium

000 poise. Poise is the unit of measurement for viscosities. Other physical properties of the sodium silicates also vary considerably depending on the relative proportions of sodium oxide and silicon dioxide present. The sodium 

Sodium silicate. Red atoms are oxygen orange atom is silicon and turquoise atoms are sodium. Gray stick indicates double bond, publishers 

Sodium silicates are made by fusing (melting) sand (silicon dioxide) and soda ash (sodium carbonate) or sodium hydroxide in a gas-fired open hearth furnace, somewhat similar to the furnaces used in the manufacture of steel. The products of this reaction are lumps of sodium silicate that are broken apart and dissolved in a stream of hot steam. The proportions of sand and soda ash used, the temperature of the reaction, and the amount of water that remains in the final product all determine the physical properties of the final product. 

About 1.1 million metric tons (1.3 million short tons) of sodium silicate was produced in the United States in 2004. The primary application for the compound is in the manufacture of soaps and detergents. It improves the cleaning ability of these products and is less damaging to metal components of dishwashers and washing machines than other ingredients of soaps and detergents. Sodium silicate 

One of the early uses of sodium silicate was as a preservative for eggs. 

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The alkali silicates are soluble in water and are used industrially. See sodium silicates. 

Corks are badly attacked and must be renewed in each run. It is preferable to employ asbestos - sodium silicate stoppers, which can be used repeatedly. 

Old rubber stoppers may be used, but are slifthtly attacked. Asbestos-sodium silicate Stoppers (for preparation, see Section III,161,Note 2) or ground glass joints are, of course, to be preferred. 

As of the mid-1990s, soluble sihcates are used primarily as sources of reactive siUca (57%), in detergency (qv) (23%), in pulp (qv) and paper (qv) production (7%), for adhesives and binders (5%), and in other appHcations (8%). The stmcture and chemistry of solutions containing polymeric siHcate species have been characterized using modem analytical techniques. This improved understanding of siHcate speciation contributes to the development of new markets. Thus, the sodium silicates constitute a versatile, stable, and growing commodity and are ranked among the top 50 commodity chemicals. 

Fig. 3. The viscosity and liquidus curves for molten sodium silicates, where the numbers on the dashed lines ate viscosity ia Pa-s (1).

Fig. 5. Viscosities of sodium silicate solutions vs percent solids A, ratio of 3.22 B, 2.4 C, 2.0 D, 1.6 and (-----), NaOH. To convert Pa-s to poise, divide...

Sodium Silicate-Oil and Hac rdous Materials—Technical Assistance Data System, National Institute of Health, Washington, D.C. (an on-line database). 

Silicate Grouts. Sodium silicate [1344-09-8] h.3.s been most commonly used in the United States. Its properties include specific gravity, 1.40 viscosity, 206 mPa-s(=cP) at 20°C Si02 Na20 = 3.22. Reaction of sodium silicate solutions with acids, polyvalent cations, such organic compounds as formamide, or their mixtures, can lead to gel formation at rates, which depend on the quantity of acid or other reagent(s) used. 

In the Shoe or one-shot method (4), formamide is used to coagulate sodium silicate. The silicate solution used in the Joosten method can be diluted with water to lower its viscosity. Concentrations of sodium silicate between 10—70% are used (viscosities of 2.5—50 mPa-s). Concentrations of formamide are between 2 and 30%. Other reactants such as CaCl2 and sodium aluminate are used in concentrations between 2.4—12 g/L of silicate solution. 

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. 

The Shoe grouting system is considered nonhazardous and nonpolluting. Sodium silicate is essentially nontoxic. Formamide is toxic and corrosive, but does not present a serious hazard if normal safety precautions are followed. Shoe chemical grout materials are two to five times more expensive than Portland cement, depending on the sodium silicate to formamide concentration ratios. Installed costs are generally more similar to those for cement grouts. 

Syneresis of sodium silicate gels may occur under some conditions, eg, in pure gels or coarse formations. Cement grouting should then precede chemical grouting. Leaching that results from dissolution under water-saturated conditions may be eliminated by use of proper reagent proportions. 

Dispersants andfloeculants. These are important for the control of slimes that sometimes interfere with the selectivity and increase reagent consumption. For example, soda ash, lime sodium silicate, and lignin sulfonates are used as dispersants, and starch and polyacrylamide are used as flocculants. 

A number of cement materials are used with brick. Standard are phenolic and furan resins, polyesters, sulfur, silicate, and epoxy-based materials. Carbon-filled polyesters and furanes are good against nonoxidizing acids, salts, and solvents. Silica-filled resins should not be used against hydrofluoric or fluosihcic acids. Sulfur-based cements are limited to 93°C (200°F), while resins can be used to about 180°C (350°F). The sodium silicate-based cements are good against acids to 400°C (750°F). 

Decreasing attack can involve pH control and chemical inhibition. Sodium silicate markedly improves the corrosion resistance of aluminum... 

It is advisable to saturate all corks with sodium silicate solution after fitting and boring them (p. 3, Note i). They are then covered with lead foil, wired in, and coated with shellac. 

Sodium silicate solution [1344-09-8] pKj 9.51, pKj 11.77 (for silicic acid, H4Si04) Purified by contact filtration with activated charcoal. 

Figure 7.10. (a) Zachariasen s two-dimensional model of an AiOj glass, after Zachariasen (1932). (b) Two-dimensional representation of a sodium silicate glass,... 

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