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Sodium silicate may be used for various paints and coatings, such as those used on welding rods. Such coatings can be cured in two ways. One method is to heat a thin layer of sodium silicate into a gel and then into a hard film. To make the coating water-resistant, high temperatures of 100 °C (212 °F; 373 K) are needed. [16]
An aqueous solution of sodium silicate is acidified to produce a gelatinous precipitate that is washed, then dehydrated to produce colorless silica gel. [6] When a visible indication of the moisture content of the silica gel is required, ammonium tetrachlorocobaltate(II) (NH 4) 2 [CoCl 4] or cobalt(II) chloride CoCl 2 is added. [6]
When the sodium silicate gel forms and swells inside a porous siliceous aggregate, it first expands and occupies the free porosity. When this latter is completely filled, and if the soluble but very viscous gel cannot be easily expelled from the silica network, the hydraulic pressure rises inside the attacked aggregate and leads to its fracture.
Sulfuric acid and sodium silicate solutions are added simultaneously with agitation to water. Precipitation is carried out under acidic or basic conditions. The choice of agitation , duration of precipitation, the addition rate of reactants, their temperature and concentration and pH can vary the properties of the resulting silica.
Sodium Metasilicate reacts with acids to produce silica gel. [6] Cements and Binders - dehydrated sodium metasilicate forms cement or binding agent. Pulp and Par - sizing agent and buffer/stabilizing agent when mixed with hydrogen peroxide. Soaps and Detergents - as an emulsifying and suspension agent.
The subunits of colloidal silica particles are typically in the range of 1 to 5 nm. Whether or not these subunits are joined depends on the conditions of polymerization. Initial acidification of a water-glass (sodium silicate) solution yields Si(OH) 4. If the pH is reduced below 7 or if salt is added, then the units tend to fuse together in chains.
This article states: silica gel is made from Na 2 SiO 3 - sodium silicate. The sodium silicate article states In acidic solutions, the silicate ion reacts with hydrogen ions to form silicic acid, which when heated and roasted forms silica gel,, while the silicic acid article states Silicic acids are formed by acidification of sodium silicate in ...
Ormosils (organically modified silicate) are obtained when silane is added to gel-derived silica during sol–gel process. The product is a molecular-scale composite with improved mechanical properties. Sono-Ormosils are characterized by a higher density than classic gels as well as an improved thermal stability. An explanation therefore might ...