silicates (from the Latin word «silex» translated as "stone") are the salt of the acid metasilicic H2SiO3.For example, sodium silicate, whose chemical formula is written as follows: Na2SiO3.Another name for salt - sodium metasilicate.The molar mass of the substance is equal to 122.06 g / mol.Appearance - white opaque crystals with a greenish tint.The density was 2.4 g / cm3.Purity has a refractive index which is equal to 1.52.Melting point - plus 1088 ° C.The substance is soluble in water and insoluble in alcohol.A dilute aqueous solution has unique properties: immersed in a freshly laid eggs can be stored up to nine months at room temperature.Sodium silicate is stable in neutral and alkaline media, and the acid anion SiO3- reacts with H + cations to form silicic acid.
silicon dioxide (also called silica or silicic anhydride) is the most stable compound that occurs naturally in the form of quartz.It accounts for 12% of the mass of the Earth's crust.Quartz contaminated with impurities is a common sand, which is formed due to the destruction of rocks.Under the action of alkali on silica chemical reaction: NaOH + SiO2 → Na2SiO3 + H2O.The result is a salt of silicic acid - sodium silicate.Hydrolysis of salt (decomposition with water) follows the scheme: 2Na2SiO3 + H2O → Na2SiO5 + 2NaOH, and formed dvumetasilikat sodium.With a decrease in concentration of the solution, the hydrolysis proceeds readily.The 1N.hydrolyzed solution of 14% salt in 0.1N.- 28% to 0.001% - 32%.Hydrolysis dvumetasilikata sodium flows already weaker.
Sodium silicate is formed by the interaction of silicon with alkali: Si + H2O + 2NaOH → Na2SiO3 + 2H2.Such a reaction can occur with weak alkalis, and is very easy with water in the presence of even a small amount of anions OH-: enough traces of alkalis extracted from the glass.Since the sodium metasilicate formed is a salt of a weak metasilicic acid, in dilute solution, it is almost completely hydrolyzed, the concentration of OH- ions in the reaction is not reduced, so that all comes down to the decomposition of the silicon water.The presence of traces of alkali are the catalyst.From 0.63 kg silicon obtained in this way 1 m3 of hydrogen, whereas iron would require almost 4 times more.In industry
different brands of sodium silicate characterized by the ratio of SiO2 and Na2O.It may vary from 2: 1 to 3.75: 1.Cultivars with a ratio of 2.85: 1 and below are considered basic.Those with a higher ratio are characterized as "neutral".Sodium silicate in form of aqueous concentrated solutions are liquid or soluble glass.But along with Na2SiO3 at present water glass and other silicates of sodium, so it is usually expressed by the composition formula, that is approximate, Na2O • nSiO2, wherein n = 2 ÷ 4.The gradual elimination of SiO2 (usually during prolonged storage) leads to a haze or waterglass to the conversion sometimes gelatinous mass.Therefore, it is held in the laboratory in containers closed with rubber stoppers as cortical or glass to the neck simply pasted.
Sodium silicate is used in the production of detergents.Annual production of liquid glass in the hundreds of thousands of tons.It is used to strengthen the soil during construction (for example, the protection of concrete floor screed against abrasion), as well as other agents such as sodium tripolyphosphate is used in many industries (both of salt, for example, are used for water softening).Impregnation Na2SiO3 automobile concrete roads greatly reduces their abrasion.
processing of wood or other material to protect against fire (for example, construction or theatrical scenery).Often it serves as a basis for refractory cements or paper glue.Simple composition putty suitable for bonding porcelain and glass.They can be prepared by mixing (to a dough consistency) chalk with liquid glass.The mixture quickly hardens and turns white and very solid ground.
of cement, mixed with the liquid glass, do quickly hardening the putty, which is used for bonding stones.The mixture of sodium silicate with sawdust is used to fill the space between the double walls of some safes.This makes them more fire resistant, and also serves as additional protection against opening by means of an acetylene torch because of the heavy smoke and alarm.