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Element Index
Samarium
Scandium
Seaborgium
Selenium
Silicon
Sodium
Strontium
Sulfur
Chemical's truth
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Sodium carbonate, monohydrate
CAS no: 5968-11-6 Formula: Na2CO3.H2O Molecular weight: 124.005
Physical Data
Appearance: Colorless orthorhombic crystals
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Melting point: 100°C (decompose)
Boiling point: -
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Density: 2.25 g/cm3
Solubility: 30.7 g/100 g H2O
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Thermodynamic Data
Enthalpy of formation: -
Gibbs energy of formation: -
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Entropy: -
Heat capacity: -
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Production and preparation
Previously, sodium carbonate was obtained from seaweed ashes, which the name 'soda ash' was derived.
The substance can now be obtained from several mineral sources such as trona, Na2CO3.NaHCO3.nH2O, and natron,
Na2CO3.
Natron, a powdery mass, encased in a plastic cover, to prevent adsorption of moisture. It is obtained from British Columbia.
The monohydrate compound also occurs as thermonatrite in nature. Alternatively, it can be obtained from the ammonia-soda (Solvay) process. It was first carried out successfully in Belgium in the 1860s to
produce sodium carbonate. It was patented in 1861 by the Belgian chemist Ernest Solvay (1838-1922). In this process, a concentrated brine is treated with ammonia and carbon
dioxide (from calcium carbonate) to give sodium bicarbonate and ammonium chloride. Ammonia is recovered when ammonium chloride is heated with lime.
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Sodium carbonate is produced by simply heating sodium bicarbonate. The decahydrate crystals can be obtained by crystallization from solutions, which decomposes at around 34°C to give the monohydrate crystals.
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Behavior and Chemical Properties
Sodium carbonate monohydrate decomposes at about 100°C to give the anhydrous compound.
It behaves as a weak alkali when dissolves in water. For example, in 19% aqueous solution the pH ~11.5. It reacts with acids to release carbon dioxide.
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When carbon dioxide is bubbled into a carbonate solution, sodium bicarbonate (hydrogen carbonate) is formed:
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History and Uses
Sodium carbonate is one of the most important starting materials in chemical manufacturing. The monohydrate compound is used mainly in photography as a constituent in developers.
In the laboratory, sodium carbonate is used in volumetric analysis to standardize acids, and in qualitatively way, for testing cations. This is because sodium carbonate solution gives
precipitates for salts of many metals as the metal carbonate or basic carbonate. In the case of insoluble salts (such as barium sulfate), it is
fused with solid sodium carbonate. Potassium carbonate is usually added to lower the melting point (fusion mixture).
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Hazard, Storage and Handling
Keep in a tightly closed container and isolate from incompatible substances, such as strong acids and aluminium. Dust is dry and fine and ensure the container is stored in a cool, dry and well-ventilated area.
Cause eye irritation and upon prolonged exposure may result skin irritation. It is only slightly toxic but harmful when ingested in large doses. The symptons may include abdominal
pain, vomiting, diarrhea and even death. Inhalation of dust may aggravate asthma and other chronic pulmonary diseases. The oral LD50 for rats is 3160 mg/kg.
Upon spillage, splash the affected area with plenty of water. If swallowed, give plenty of water or milk to drink and seek medical advice. Do not induce vomiting. Do not give acidic fluids such as carbonated drinks or vinegar.
Avoid breathing dust.
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(Last update: March 2006) |
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