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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]
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. It is a colorless crystalline hygroscopic and deliquescent solid, soluble in water (giving an alkaline solution) but not in alcohols. [1]
Silicates with alkali cations and small or chain-like anions, such as sodium ortho-and metasilicate, are fairly soluble in water. They form several solid hydrates when crystallized from solution. Soluble sodium silicates and mixtures thereof, known as waterglass are important industrial and household chemicals. Silicates of non-alkali cations ...
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.
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.
For the production of 4A sieve, typically aqueous solutions of sodium silicate and sodium aluminate are combined at 80 °C. The product is "activated" by "heating" at 400 °C [15] 4A sieves serve as the precursor to 3A and 5A sieves through cation exchange of sodium for potassium (for 3A) or calcium (for 5A) [16] [17]
This is because all the fluid inside the membrane is too dense to float and thereby exerts a downward force. The concentration of sodium silicate becomes important in growth rate. After the growth has ceased, the sodium silicate solution can be removed by a continuous addition of water at a very slow rate. This prolongs the life of the garden. [6]
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]