The salts of silicic acids ( H4SiO4 ) are known as silicate.
The compounds derived from silicic acids are call-ed silicate.
1- Sodium silicate , Na2SiO3:
It is sodium Salt of meta Silicic acid, H2SiO3. It is also water glass or soluble glass.Sodium Silicates is prepare by heating mixture of sand and sodium carbonate in a reverberatory furnace.
Na2CO3 + Si2 → Na2SiO3 + CO2
Properties Of Sodium Silicate :
- It is Soluble in water.
- Its aqueous solution is strongly alkaline due to hydrolysis.
Uses of Sodium Silicates:
- Sodium Silicate is use as a filter for soap.
- It is use as a fire proof in textiles.
- It is use as furniture Polish.
- Sodium Silicate is use for Preserving eggs.
- It is use in CaliCO Printing.
When Crystals of Soluble color salts like NiCl2 , FeSO4, CuSO4 or Co(NO3)2 are put in solution of sodium silicate then beautiful growth like plant is produce. It is call as Chemical Garden.
2- Aluminum Silicate:
The Formula of Aluminum Silicate is H2Al2 (SiO4)2.H2O OR Al2O3.2SiO2.2H2O. It is also Call-ed Kaolin Or Pottery Clay.
Due to weathering conditions the complex silicates in rocks change into simple silicates. The formation of Aluminum Silicates is the result of weathering on the rocks. The chemical reaction of water and carbon dioxide with potassium feldspar gives Aluminum silicates.
Properties Of Aluminum Silicate :
- Pure clay is white. It is call as Kaolin.
- Ordinary clay is yellow or reddish yellow. It is due to compounds of iron or other metals.
- Improve clay is easily fusible due to presence of oxides of iron,Calcium,Magnesium etc.
- The articles of impure clay turn reddish on heating. It is due to presence of ferric Oxide.
- When clay is soak in water, then it shows hydration and becomes plastic. On heating water of hydration removes and hard rock like mass is form.
- China wares are made of Kaolin, bone ash, feldspar.
Uses Of Aluminum Silicates ( Clay):
- Pure Clay is use to make porcelain and china wares.
- Impure clay is use to make bricks tiles and stone wares.
- Clay is the main Component of cement.
Glazing Of Clay Articles:
The clay articles are porous. We can Change Porous Article into non Porous articles by throwing salt upon then at high temperature. It is Call as glazing.
In this process salt react with clay and produces sodium aluminate and sodium aluminium silicates. They melt readily and fill and cover the surface pores. On cooling Surface becomes compact, china wares are glazed.
3- Talc Or Soapstone:
Magnesium Silicate, Mg3H2(SiO3)4 is call as Talc or Soapstone. It is greasy to touch. It is use to make household articles. Talc is also use to make cosmetics.
It is Hydrate calcium – Magnesium Silicate, CaMg(SiO3)4. It is use in making incombustible (fire proof) fabrics and hard board.