Introduction to Sodium Silicate
The sodium silicate or water glass is the technical and common name for a mixture of compounds, chiefly the metasilicate (sodium oxide and silica ). Its formula is Na2Sio3.
The commercial product is available in water solution or in solid form. It is often greenish or blue owing to the presence of iron-containing impurities.
History of Sodium Silicate
The observation began since the year 1500 by European alchemists. But the terms “water glass” and “soluble glass” were used by Leopold Wolff in 1846, by Émile Kopp in 1857 and by Hermann Krätzer in 1887.
In 1892, Rudolf Von Wagner gave us soda, potash, double (soda and potash), and fixing as types of water glass. The fixing is a combination of several compounds.
Well-saturated silica is included here along with the inclusion of potash water glass and sodium silicate. It is also used to stabilize inorganic watercolour pigments on cement work for outdoor signs and murals.
Properties of Sodium Silicate
Sodium silicates are either colourless glassy or crystalline solids or white powders. It is readily soluble in water except for the most silicon-rich ones, producing alkaline solutions. It is a stable compound in neutral and alkaline solutions.
In acidic solutions, the reaction of silicate ions takes place with hydrogen ions to form silicic acids, which tend to decompose into hydrated silicon dioxide gel. When this gel is heated it results in a hard translucent substance which is silica gel, widely used as a desiccant. It can withstand temperatures up to 1100°.
Production of Sodium Silicate
Treating a mixture of silica (usually as quartz sand), caustic soda, and water, with hot steam in a reactor produces solutions of sodium silicates. The overall reaction is
2 x NaOH + SiO2 → (Na2O) x SiO2 + x H2O
These substances are also obtainable by dissolving silica SiO2 in molten sodium carbonate. The compound is also obtainable from sodium sulfate (melting point 884 °C) with carbon as a reducing agent.
Sodium Silicate Uses
As a Cohesive- The largest application of this substance is as cement for producing cardboard. When used as a paper cement, the sodium silicate joint tends to crack within a few years. At this point, it no longer binds the cementing paper surfaces together.
Detergent supplemental- Its use takes place in detergent auxiliaries such as complex sodium disilicate and modified sodium disilicate. The detergent particles gain their ruggedness from a coating of silicates.
Water treatment- Use of this substance takes place as an alum coagulant and an iron flocculant in wastewater treatment plants. Sodium silicate holds colloidal molecules, creating larger aggregates that sink to the bottom of the water column.
Drilling fluids- This substance is quite useful in drilling fluids to stabilize borehole walls and to avoid the collapse of bore walls. It is very useful when drill holes pass through argillaceous formations containing swelling clay minerals such as smectite or montmorillonite.
In Automotive Industry repair- Sodium silicate is effective helps in repairing mufflers, resonators, tailpipes, and other exhaust components, with and without fibreglass reinforcing tapes.
Safe construction- A mixture of sodium silicate and sawdust (or wood shavings) is useful between the double skin of certain safes. This not only makes them more fire-resistant but also hard to cut with an oxyacetylene torch.
Pottery- Sodium silicate is a compound which helps in casting slips to reduce viscosity and the need for large amounts of water to liquidize the clay body. It is also effective in creating a crackle effect in pottery, usually wheel-thrown.
Solved Questions For You
Q.1. What is the pH of sodium silicate?
Ans- All silicate solutions happen to be alkaline. Furthermore, the pH of commercial silicate solutions ranges from approximately 10 to 13.
The pH decreases with increasing silica content. pH value influences the stability of a sodium silicate solution.
Q.2. Which country produces the highest amount of sodium silicate?
Ans- According to an estimate, China is to be the leading market for sodium silicate in the Asia Pacific. Other major countries like India, Japan, and South Korea are also contributing a lot to the growth of the sodium silicate market.