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Sodium silicate solutions can also be used as a spin-on adhesive layer to bond glass to glass [21] or a silicon dioxide–covered silicon wafer to one another. [22] Sodium silicate glass-to-glass bonding has the advantage that it is a low-temperature bonding technique, as opposed to fusion bonding. [21]
Sodium metasilicate is the chemical substance with formula Na 2 SiO 3, which is the main component of commercial sodium silicate solutions. It is an ionic compound consisting of sodium cations Na + and the polymeric metasilicate anions [– SiO 2− 3 –] n.
Sodium silicide (NaSi, Na 4 Si 4) is a binary inorganic compound consisting of sodium and silicon. It is a solid black or grey crystalline material. [1] Sodium silicide reacts readily with water yielding gaseous hydrogen and aqueous sodium silicate in an exothermic reaction (~175 kJ·mol −1): [2] 2 NaSi + 5 H 2 O → 5 H 2 + Na 2 Si 2 O 5
Sodium fluorosilicate is used in some countries as additives for water fluoridation, opal glass raw material, ore refining, or other fluoride chemical (like sodium fluoride, magnesium silicofluoride, cryolite, aluminum fluoride) production. [5] It also is an ingredient in some ceramic cements.
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.
Sodium orthosilicate is the chemical compound with the molecular formula Na 4 SiO 4. It is one of the sodium silicates, specifically an orthosilicate, formally a salt of the unstable orthosilicic acid H 4 SiO 4. [2] [3] [4]
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]
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.