Sodium Carbonate anhydrous 99% 1Kg
Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, water-soluble salts. All forms have a strongly alkaline taste and give moderately alkaline solutions in water. Historically it was extracted from the ashes of plants growing in sodium-rich soils. Because the ashes of these sodium-rich plants were noticeably different from ashes of wood (once used to produce potash), sodium carbonate became known as “soda ash.” It is produced in large quantities from sodium chloride and limestone by the Solvay process.
Hydrates
Sodium carbonate is obtained as three hydrates and as the anhydrous salt:
- sodium carbonate decahydrate (natron), Na2CO3·10H2O, which readily effloresces to form the monohydrate.
- sodium carbonate heptahydrate (not known in mineral form), Na2CO3·7H2O.
- sodium carbonate monohydrate (thermonatrite), Na2CO3·H2O. Also known as crystal carbonate.
- anhydrous sodium carbonate (natrite), also known as calcined soda, is formed by heating the hydrates. It is also formed when sodium hydrogencarbonate is heated (calcined) e.g. in the final step of the Solvay process.
The decahydrate is formed from water solutions crystallizing in the temperature range −2.1 to +32.0 °C. The heptahydrate in the narrow range 32.0 to 35.4 °C and above this temperature the monohydrate forms. In dry air the decahydrate and heptahydrate lose water to give the monohydrate. Other hydrates have been reported, e.g. with 2.5 units of water per sodium carbonate unit (“pentahemihydrate”).
Washing soda
Sodium carbonate decahydrate (Na2CO3·10H2O), also known as washing soda, is the most common hydrate of sodium carbonate containing 10 molecules of water of crystallization. Soda ash is dissolved in water and crystallized to get washing soda.
- {\displaystyle {\ce {Na2CO3 + 10H2O -> Na2CO3.10H2O}}}
- It is white crystalline solid;
- It is one of the few metal carbonates which are soluble in water;
- It is alkaline; it turns red litmus to blue;
- It has detergent properties through the process of saponification which makes fats and grease water-miscible.
Applications
Some common applications of sodium carbonate (or washing soda) include:
- Sodium carbonate (or washing soda) is used as a cleansing agent for domestic purposes like washing clothes. Sodium carbonate is a component of many dry soap powders.
- It is used for removing temporary and permanent hardness of water. (see water softening).
- It is used in the manufacture of glass, soap and paper. (see glass manufacture)
- It is used in the manufacture of sodium compounds like borax.
Glass manufacture
Sodium carbonate serves as a flux for silica, lowering the melting point of the mixture to something achievable without special materials. This “soda glass” is mildly water-soluble, so some calcium carbonate is added to the melt mixture to make the glass insoluble. Bottle and window glass (soda-lime glass) is made by melting such mixtures of sodium carbonate, calcium carbonate, and silica sand (silicon dioxide (SiO2)). When these materials are heated, the carbonates release carbon dioxide. In this way, sodium carbonate is a source of sodium oxide. Soda-lime glass has been the most common form of glass for centuries. It is also a key input for tableware glass manufacturing.
Water softening
Hard water contains dissolved compounds, usually calcium or magnesium compounds. Sodium carbonate is used for removing temporary and permanent hardness of water.
As sodium carbonate is water-soluble and magnesium carbonate and calcium carbonate are insoluble, the former is used to soften water by removing Mg2+ and Ca2+. These ions form insoluble solid precipitates upon treatment with carbonate ions:
- {\displaystyle {\ce {Ca^2+ + CO3^2- -> CaCO3}}}
- {\displaystyle {\ce {Ca^2+(aq) + Na2CO3(aq) -> CaCO3(s) + 2Na+(aq)}}}
Similarly, {\displaystyle {\ce {Mg^2+(aq) + Na2CO3(aq) -> MgCO3(s) + 2Na+(aq)}}}
The water is softened because it no longer contains dissolved calcium ions and magnesium ions.
Physical properties
The integral enthalpy of solution of sodium carbonate is −28.1 kJ/mol for a 10% w/w aqueous solution. The Mohs hardness of sodium carbonate monohydrate is 1.3.
Occurrence as natural mineral
Sodium carbonate is soluble in water, and can occur naturally in arid regions, especially in mineral deposits (evaporites) formed when seasonal lakes evaporate. Deposits of the mineral natron have been mined from dry lake bottoms in Egypt since ancient times, when natron was used in the preparation of mummies and in the early manufacture of glass.
The anhydrous mineral form of sodium carbonate is quite rare and called natrite. Sodium carbonate also erupts from Ol Doinyo Lengai, Tanzania’s unique volcano, and it is presumed to have erupted from other volcanoes in the past, but due to these minerals’ instability at the earth’s surface, are likely to be eroded. All three mineralogical forms of sodium carbonate, as well as trona, trisodium hydrogendicarbonate dihydrate, are also known from ultra-alkaline pegmatitic rocks, that occur for example in the Kola Peninsula in Russia.
Extraterrestrially, known sodium carbonate is rare. Deposits have been identified as the source of bright spots on Ceres, interior material that has been brought to the surface. While there are carbonates on Mars, and these are expected to include sodium carbonate, deposits have yet to be confirmed, this absence is explained by some as being due to a global dominance of low pH in previously aqueous Martian soil.