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Sodium silicate, also known as water glass, is a compound used in cements and textile processing.
Sodium carbonate and silicon dioxide react when molten to form sodium silicate and carbon dioxide.
Sodium silicate is a white solid that is soluble in water, producing an alkaline solution. There are many kinds of this compound, including sodium orthosilicate, Na4SiO4; sodium metasilicate, Na2SiO3; sodium polysilicate, (Na2SiO3)n; sodium pyrosilicate, Na6Si2O7, and others. All are glassy, colourless and dissolve in water.
Sodium silicate is stable in neutral and alkaline solutions. 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 that absorbs water readily.
Sodium silicate was 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.
Texas A&M University recently received a patent on using sodium silicate in a refining process for vegetable oil that removes fatty acids and other impurities. The process uses sodium silicate and filtration instead of sodium hydroxide and centrifuges. Sodium silicate commands a 50 to 100 percent price premium over sodium hydroxide, and the process needs the equivalent to 0.5 to 1 percent of it to the volume of crude vegetable oil as a neutralizing agent, depending on the acidity of the oil.
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