Occurrence
Ash is a tree found in regions of North America
History
Sodium carbonate, Na2CO3, has been used historically for making glass, soap, and gunpowder. Along with potassium carbonate, known as potash, sodium carbonate was the basis of the alkali industry, which was one of the first major chemical industries. Throughout history, alkalis were obtained from natural sources. Soda ash was also produced by burning wood and leaching the ashes with water to obtain a solution that yielded soda ash when the water was boiled off. The name soda ash originates from the barilla plant, which was used to produce soda ash. The scientific name of this plant is Salsola soda, but it goes by the common names of sodawort or glasswort because the soda produced from it was used in making glass. Barilla is a common plant found in saline waters along the Mediterranean Sea in Spain and Italy.
Barilla was dried and burned to produce soda ash. The depletion of European forests and
international disputes made the availability of alkali salts increasingly uncertain during the
latter part of the 18th century. LeBlanc
proposed a procedure in 1783, and a plant based on LeBlanc’s method was opened in 1791.
Unfortunately, LeBlanc’s association with French Royalty led to the confi scation of the plant
at the time of the French Revolution. Furthermore, confl icting claims for LeBlanc’s method
were made by several other chemists and he never received the reward.
Definition
A
dibasic acid formed in small amounts in solution
when carbon dioxide dissolves in
water:
CO2 + H2O?H2CO2
It forms two series of salts: hydrogencarbonates
(HCO3–) and carbonates (CO32-).
The pure acid cannot be isolated.
Definition
sodium carbonate: Anhydrous sodium carbonate (soda ash, sal soda) is a white powder, which cakes and aggregates on exposure to air due to the formation of hydrates. The monohydrate, Na2CO3·H2O, is a white crystalline material, which is soluble in water and insoluble in alcohol; r.d. 2.532; loses water at 109°C; m.p. 851°C.
The decahydrate, Na2CO3·10H2O (washing soda), is a translucent efÛorescent crystalline solid; r.d. 1.44; loses water at 32–34°C to give the monohydrate; m.p. 851°C.
Sodium carbonate may be manufactured by the Solvay process or by suitable crystallization procedures from any one of a number of natural deposits, such as:
trona (Na2CO3·NaHCO3·2H2O),
natron (Na2CO3·10H2O),
ranksite (2Na2CO3·9Na2SO4·KCl),
pirsonnite (Na2CO3·CaCO3·2H2O),
gaylussite (Na2CO3·CaCO3·5H2O).
The method of extraction is very sensitive to the relative energy costs and transport costs in the region involved. Sodium carbonate is used in photography, in cleaning, in pH control of water, in textile treatment, glasses and glazes, and as a food additive and volumetric reagent.
Production Methods
Sodium carbonate is produced on all continents of the world
from its minerals. It is present in large deposits in Africa and the United States as either carbonate or trona, a mixed ore of
equal molar amounts of carbonate and bicarbonate. However,
about 70% of the world production of sodium carbonate is
manufactured by the Solvay (ammonia soda) process,
whereby ammonia is added to a solution of sodium chloride.
Carbon dioxide is then bubbled through to precipitate the
bicarbonate (NaHCO3) that is decomposed by heat-producing
sodium carbonate. In the United States. all production is
based on the minerals that contain sodium carbonate. Different
qualities of sodium carbonate are produced: technical,
food, and pharmaceutical grades.
General Description
Sodium carbonate is a water soluble inorganic salt commonly used as a weak base. Its aqueous solution has the ability to uptake carbon dioxide. It can also catalyze the conversion of sewage sludge to liquid fuels.
Flammability and Explosibility
Nonflammable
Biochem/physiol Actions
Buffer component, may be used for the removal of peripheral membrane proteins.
Purification Methods
It crystallises from water as the decahydrate which is redissolved in water to give a near-saturated solution. By bubbling CO2, NaHCO3 is precipitated. It is filtered off, washed and ignited for 2hours at 280o [MacLaren & Swinehart J Am Chem Soc 73 1822 1951]. Before being used as a volumetric standard, analytical grade material should be dried by heating at 260-270o for 0.5hour and allowed to cool in a desiccator. It has a transition point at 450o, and its solubility in water is 21.58% at 20o (decahydrate in solid phase), 49.25% at 35o (heptahydrate in solid phase) and 44.88% at 75o(monohydrate in solid phase) [D.nges in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 987-988 1963]. After three recrystallisations, technical grade Na2CO3 had Cr, Mg, K, P, Al, W, Sc and Ti at 32, 9.4, 6.6, 3.6, 2.4, 0.6, 0.2 and 0.2 ppm respectively; another technical source had Cr, Mg, Mo, P, Si, Sn and Ti at 2.6, 0.4, 4.2, 13.4, 32, 0.6, 0.8 ppm respectively.
