What is Sodium Silicate?

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Sodium silicate crystals

Sodium silicate, usually known as "water glass" or “liquid glass”, is well-known due to wide commercial and industrial application. It is mostly composed of oxygen-silicon polymer backbone lodging water in molecular matrix pores. Sodium silicate products are manufactured as solids or thick liquids, depending on proposed use. For instance, water glass functions as a sealant in metal components. Finally, even though, sodium silicate manufacture is a mature industry, there is current research for new applications given its heat conductive properties. Sodium silicate is a versatile, inorganic chemical made by combining various ratios of sand and soda ash (sodium carbonate) at high temperature. This process yields a variety of products with unique chemistry that are used in many industrial and consumer applications.


What is the History of Sodium Silicate?

Sodium silicate was first observed by Van Helmont, a chemist, in 1640 as a fluid substance made by melting sand with excess alkali (base that dissolves in water). Water Glass was defined in Von Wagner's Manual of Chemical Technology, in 1892, as any of the soluble alkaline silicates, which was first observed by Van Glaber, a German chemist made “fluid silica” in 1648 from potash and silica. Von Fuchs, another chemist, in 1825, obtained what is now known as water glass by treating silicacid with an alkali, the result being soluble in water. Von Wagner distinguished soda, potash, double (soda and potash), and fixin as types of water glass. The fixing type was "a mixture of silica well saturated with potash water glass and a sodium silicate" used to stabilize inorganic water color pigments on cement work for outdoor signs.


What are the properties of Sodium silicate?

  • Sodium silicate is a white powder that is readily soluble in water, producing an alkaline solution.
  •  It is one of a number of related compounds like, sodium ortho silicate, sodium pyro silicate, etc. All are glassy, colorless and dissolve in water.
  •  Sodium silicate is stable in neutral and alkaline. In acidic solutions, the silicate ion reacts with hydrogen ions to form silicic acid, which when heated and roasted forms silica gel, a hard, glassy substance.
  •  Liquids and solids based on sodium silicate and produced by PQ Corporation have a density from 1.6g/cubic cm. to about 1.4 g/cubic cm.


How is Sodium silicate synthesized?

A synthesis scheme for the substance involves a combination of sodium carbonate (Na2CO3) and silicon dioxide (SiO2) under conditions sufficient to melt both reactants. Sodium silicate is produced by this method with sufficient efficiency to be of commercial use. The chemical reaction is given as:

Na2CO3 + SiO2 → Na2SiO3 + CO2


What are the Uses of sodium Silicate?

  •  In Metal repair: Sodium silicate is used, along with magnesium silicate, in muffler repair and fitting paste. Muffler is a device for reducing the amount of noise emitted by the exhaust of an internal combustion engine. When dissolved in water, both sodium silicate, and magnesium silicate form a thick paste that is easy to apply. When the exhaust system of an internal combustion engine heats up to its operating temperature, the heat drives out all of the excess water from the paste. The silicate compounds that are left over have glass-like properties, making a temporary, brittle repair.
  •  In Automotive repair leaks: Sodium silicate can be used to seal leaks at the head gasket. A head gasket is a gasket that sits between the engine block and cylinder head in an internal combustion engine. A common use is when an alloy cylinder head engine is left sitting for extended periods or the coolant is not changed at proper intervals, electrolysis can "eat out" sections of the head causing the gasket to fail. Rather than remove the cylinder head, "liquid glass" is poured into the radiator and allowed to circulate. The waterglass is injected via the radiator water into the hotspot at the engine.
  •  Car engine disablement: Sodium silicate solution is used to inexpensively, quickly, and permanently disable automobile engines.
  • As Adhesive: Sodium silicate was used to seal combustible nitrated paper together to form a conical paper cartridge to hold the black powder, as well as to cement the lead ball or conical bullet into the open end of the paper cartridge. One common example of its use as paper cement was for producing paper cartridges for black powder revolvers especially during the American Civil War.
  •  Aquaculture: Aquaculture Sodium silicate gel is also used as a substrate algal growth in aquaculture hatcheries.
  •  In Food preservation: Sodium silicate was also used as an egg preservation agent in the early 20th century with large success. When fresh eggs are immersed in it, bacteria which cause the eggs to spoil are kept out and water is kept in. Eggs can be kept fresh using this method for up to nine months.
  •  As a Passive fire protection: Sodium silicates are inherently intumescent (substance which swells as a result of heat exposure,). They come in prill (solid beads) form, as well as the liquid, water glass. The solid sheet form (Palusol) must be waterproofed to ensure long term passive fire protection. Standard, solid, bead form sodium silicates have been used as aggregate within silicone rubber to manufacture plastic pipe firestop devices.
  •  Refractory use: Water glass is a useful binder of solids, such as vermiculite, the natural mineral that expands with the application of heat and perlite, volcanic glass that has a relatively high water content. When blended with the above light weight aggregates, water glass can be used to make hard, high-temperature insulation boards used for refractory.
  •  Concrete treatment: Concrete treated with a sodium silicate solution helps to significantly reduce porosity in most products such as concrete.
  •  Drilling Fluids: Sodium silicate is frequently used in drilling fluids to stabilize borehole wells and to avoid the collapse of bore walls. 


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