Sodium Carbonate

OVERVIEW

Sodium carbonate (SO-dee-um KAR-bun-ate) is an odorless white powder or crystalline solid with an alkaline taste. (Baking soda is another substance with an alkaline taste.) It is hygroscopic, meaning that it has a tendency to absorb moisture from the air. It also exists as the monohydrate (Na₂CO₃·H₂O) and as the decahydrate (Na₂CO₃·10H₂O), each with slightly different physical properties from those of the anhydrous salt. The anhydrous form of sodium carbonate is commonly known as soda ash, while the decahydrate is often called sal soda or washing soda. Sodium carbonate has long been one of the most important chemical compounds produced in the United States. Its primary use is in the manufacture of glass and other chemicals.

KEY FACTS

OTHER NAMES:

Anhydrous salt: soda ash; Solvay soda; decahydrate: sal soda; washing soda (see Overview)

FORMULA:

Na₂CO₃

ELEMENTS:

Sodium, carbon, oxygen

COMPOUND TYPE:

Salt (inorganic)

STATE:

Solid

MOLECULAR WEIGHT:

105.99 g/mol

MELTING POINT:

858.1°C (1576°F)

BOILING POINT:

Not applicable; begins to decompose below melting point

SOLUBILITY:

Soluble in water; insoluble in ethyl alcohol

HOW IT IS MADE

Humans have known about and used sodium carbonate for thousands of years. The ancient Egyptians extracted the compound from a mineral known as natron found in dry lake bottoms. Natron is a combination of sodium carbonate and sodium bicarbonate. The Egyptians used sodium carbonate in the mummification of dead bodies. The compound dried out the bodies of the dead and prevented them from decaying. The technique was so effective that some mummified bodies over 3,000 years old are in as good a condition today as they were when the person died. Over the centuries, sodium carbonate was also produced by the combustion of organic matter, especially seaweed. This method of production accounts for the compound's common name of soda ash (ash containing sodium compounds).

The burning of dead plants does not produce very large quantities of sodium carbonate, so early chemists searched for synthetic methods of producing the increasingly important compound. The first breakthrough in that search occurred in 1791 when French chemist Nicolas Leblanc (1742–1806) invented a method for making sodium carbonate that became the industry standard for nearly a century. In the Leblanc method, sodium chloride (NaCl) is treated with sulfuric acid (H₂SO₄) to make sodium sulfate (Na₂SO₄) and hydrochloric acid (HCl). The sodium sulfate is then heated with charcoal (nearly pure carbon) and limestone (CaCO₃). The product of this reaction is a dark ashy material that contains sodium carbonate, calcium sulfide, carbon dioxide, and other byproducts:

Na₂SO₄ + 2C + CaCO₃ → Na₂CO₃ + CaS + 2CO₂

The sodium carbonate is extracted from this mixture and purified. The Leblanc invention was one of the great breakthroughs in the early years of chemical science. It made possible, among other things, the mass production of soap for the first time in human history.

As important as Leblanc's invention was, it suffered from one serious drawback: It required large amounts of energy. For this reason, chemists were always on the lookout for an alternative method for producing sodium carbonate that was less energy-intensive. That breakthrough came in 1861 when Belgian chemist Ernest Solvay (1838–1922) found a new way to make the important compound. Solvay found that treating sodium chloride with carbon dioxide and ammonia resulted in the formation of sodium bicarbonate and ammonium bicarbonate. Simply heating the sodium bicarbonate converts the bicarbonate to the carbonate. Like Leblanc's discovery, the Solvay process is regarded as one of the great accomplishments in the first century of industrial chemistry. By 1900, almost all of the sodium carbonate produced in the world was being made by the Solvay process.

That situation has changed. Today the most important source of sodium carbonate is natural minerals, such as thermonatrite (sodium carbonate monohydrate; Na₂CO₃·H₂O) or natron (or natrite; sodium carbonate decahydrate; Na₂CO₃·10H₂O). These minerals are obtained from rocky deposits or from brines that are rich in the compound. Brine is water that is saturated with salts, such as sodium chloride, potassium chloride, and sodium carbonate. It is similar to, but saltier than, seawater.

COMMON USES AND POTENTIAL HAZARDS

About half of all the sodium carbonate produced in the United States is used to make glass products such as glass containers, flat glass, and fiber insulation. Glass is made by fusing (melting) a mixture of silica (silicon dioxide; SiO₂), sodium carbonate, limestone (calcium carbonate; CaCO₃), and other materials. The recipe differs considerably depending on the type of glass one wishes to make. For example, oxides of various metals such as iron(III) oxide and copper(II) oxide are added to provide a reddish tint to the glass.

The second highest use of sodium carbonate is in the production of other chemical compounds, followed by the compound's use in the production of soaps and detergents. Other applications of the compound include:

• The production of pulp and paper products;
• The removal of sulfur dioxide from flu gases in factories;
• In water purification and waste water treatment facilities;
• As a mordant in the dyeing of cloth;
• In the refining of petroleum;
• As a catalyst in the process by which coal is converted into a liquid fuel;
• For the bleaching of cotton and linen fabrics;
• As an emetic (a compound that induces vomiting); and
• In cosmetics and personal care products because of its ability to clean skin and help clear up rashes.

Interesting Facts

• Over the last decade, consumption of sodium carbonate in the United States has been decreasing, largely because glass containers (made with sodium carbonate) are being replaced by plastic containers. However, the industry has not gone into decline primarily because the demand for glass in developing countries continues to increase at a rate that matches the decline in glass bottle demand in the United States.

No serious health hazards have been associated with the use of sodium carbonate in any of its forms.

Words to Know

ANHYDROUS

Lacking water of hydration.

CATALYST

A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure.

MORDANT

A substance used in dyeing and printing that reacts chemically with both a dye and the material being dyed to help hold the dye permanently to the material.

SYNTHESIS

A chemical reaction in which some desired chemical product is made from simple beginning chemicals, or reactants.

WATER OF HYDRATION

Water that has combined with a compound by some physical means.

FOR FURTHER INFORMATION

Kiefer, David M. "Soda Ash, Solvay Style." Today's Chemist (February 2002): 87-88+. Also available online at http://pubs.acs.org/subscribe/journals/tcaw/11/i02/html/02chemchron.html (accessed on November 8, 2005).

Lister, Ted, compiler. "Sodium Carbonate—A Versatile Material." Royal Society of Chemistry. http://www.chemsoc.org/pdf/LearnNet/rsc/SodiumCarb_sel.pdf (accessed on November 8, 2005).

Monet, Jefferson. "An Overview of Mummification in Ancient Egypt." TourEgypt.net. http://www.touregypt.net/featurestories/mummification.htm (accessed on November 8, 2005).

"Soda Ash or Trona." Mineral Information Institute. http://www.mii.org/Minerals/phototrona.html (accessed on November 8, 2005).

"Sodium Carbonate." United Nations Environmental Programme. http://www.inchem.org/documents/sids/sids/Naco.pdf (accessed on November 8, 2005).

See AlsoSodium Bicarbonate

Sodium Carbonate

Manufacture of sodium carbonate

Properties of sodium carbonate

Uses of sodium carbonate

Resources

Sodium carbonate, also known as washing soda, is a sodium salt of cabonic acid, with a chemical compound that conforms to the general formula: Na₂CO₃.

It is commonly referred to as soda ash because it was originally obtained from the ashes of burnt seaweed. For over one hundred years, soda ash is manufactured primarily by a method known as the Solvay process (also called the ammonia-soda process). Currently, it is one of the top industrial chemicals, in terms of volume, produced in the United States. It is mostly used in the manufacture of glass, but is also used in the manufacture of other products and is an important precursor to many of the sodium compounds used throughout industry.

Manufacture of sodium carbonate

The process for obtaining sodium carbonate has changed significantly over time. Burning seaweeds, which were rich in sodium, originally produced it. When the weeds were burned, sodium would be left in the ashes in the form of sodium carbonate. Although this process was effective, it could not be used to produce large volumes. Sodium carbonate has been used in various forms since ancient times. In ancient Egypt, for instance, natron, which is a mineral of sodium carbonate and sodium bicarbonate, was mined so that it could be used to make glass and as an ingredient to mummify dead bodies.

The first process that allowed production of significant amounts of sodium carbonate was a synthetic process known as the LeBlanc process, developed by French chemist Nicolas LeBlanc (1742–1806). In this process, salt (sodium chloride) was reacted with sulfuric acid to produce sodium sulfate and hydrochloric acid. The sodium sulfate was heated in the presence of limestone and coal and the resulting mixture contained calcium sulfate and sodium carbonate, which was then extracted out.

Two significant problems with the LeBlanc process, high expense and significant pollution, inspired Belgian chemical engineer Ernest Solvay (1838–1922) to develop a better process for creating sodium carbonate. In the Solvay process, ammonia and carbon dioxide are used to produce sodium carbonate from salt and limestone. Initially, the ammonia and carbon dioxide are reacted with water to form the weak electrolytes ammonium hydroxide and carbonic acid. These ions react further and form sodium bicarbonate. Since the bicarbonate barely dissolves in water, it separates out from the solution. At this point, the sodium bicarbonate is filtered and converted into sodium carbonate by heating.

Synthetic production is not the only method of obtaining sodium carbonate. A significant amount is mined directly from naturally occurring sources. The largest natural sources for sodium carbonate in the United States are found around Green River, Wyoming, and in dried-up Lake Searles within the Mojave Desert in California.

Properties of sodium carbonate

At room temperature, sodium carbonate (Na₂CO₃) is an odorless, grayish white powder that is hygroscopic. This property means when it is exposed to air, it can spontaneously absorb water molecules. Another familiar compound that has this hygroscopic quality is sugar. Sodium carbonate has a melting point of 1,564°F (851°C), a density of 2.53 g/cm³, and is soluble in water. A water solution of soda ash has a basic pH and a strong alkaline taste. When it is placed in a slightly acidic solution, it decomposes and forms bubbles. This effect, called effervescence, is found in many commercial antacid products that use sodium carbonate as an active ingredient.

Anhydrous (without water) sodium carbonate can absorb various amounts of water and form hydrates that have slightly different characteristics. When one water molecule per molecule of sodium carbonate is absorbed, the resulting substance, sodium carbonate monohydrate, is represented by the chemical formula Na₂CO₃• H₂O. This compound has a slightly lower density than the anhydrous version. Another common hydrate is formed by the absorption of ten water molecules per molecule of sodium carbonate. This compound, Na₂CO₃• 10H₂O, known as sodium carbonate decahydrate, exists as transparent crystals that readily effervesce when exposed to air.

Uses of sodium carbonate

Sodium carbonate is utilized by many industries during the manufacture of different products. The most significant user is the glass industry, which uses sodium carbonate to decompose silicates for glass making. The cosmetic industry uses it for manufacturing soap. The chemical industry uses it as a precursor to numerous sodium containing reagents. It is also important in photography, the textile industry, and water treatment. In addition to these industrial applications, sodium carbonate is used in medicine as an antacid. Around the house, sodium carbonate is used as a water softener for laundry, which is why it is sometimes called washing soda. Used for this purpose, it helps to remove stains from alcohol, grease, oil, and others.

KEY TERMS

Anhydrous —A compound which does not contain any absorbed water.

Hydrate —A compound which contains a certain amount of absorbed water.

Hygroscopic —A compound which has a tendency to absorb water molecules.

LeBlanc process —A method of sodium carbonate production using salt, limestone, and coal.

Soda ash —A name for sodium carbonate which reflects its original source, the ashes of burnt seaweed.

Solvay process —The current synthetic method of sodium carbonate production from ammonia, carbon dioxide, salt, and limestone.

Resources

BOOKS

Carey, Francis A. Organic Chemistry. Dubuque, IA: McGraw-Hill, 2006.

Faith, W.L., Donald Keyes, and Ronald Clark. Industrial Chemicals. New York: John Wiley & Sons, 1966.

Hester, R.E. and R.M. Harrison, eds. Chemicals in the Environment: Assessing and Managing Risk. Cambridge, UK: Royal Society of Chemistry, 2006.

Hoffman, Robert V. Organic Chemistry: An Intermediate Text. Hoboken, NJ: Wiley-Interscience, 2004.

Lide, David R., ed. CRC Handbook of Chemistry and Physics Boca Raton, FL: CRC Press, 2005.

The Merck Index. Whitehouse Station, NJ: Merck, 2001.

Snyder, C.H. The Extraordinary Chemistry of Ordinary Things. 4th ed. New York: John Wiley and Sons, 2002.

Perry Romanowski

Sodium carbonate

Sodium carbonate is a chemical compound which conforms to the general formula Na2CO3.

It is commonly referred to as soda ash because it was originally obtained from the ashes of burnt seaweed. Now, soda ash is primarily manufactured by a method known as the Solvay process. Currently, it is one of the top industrial chemicals, in terms of volume , produced in the United States. It is mostly used in the manufacture of glass , but is also used in the manufacture of other products and is an important precursor to many of the sodium compounds used throughout industry.

Manufacture of sodium carbonate

The process for obtaining sodium carbonate has changed significantly over time. It was originally produced by burning seaweeds that were rich in sodium. When the weeds were burned, sodium would be left in the ashes in the form of sodium carbonate. Although this process was effective, it could not be used to produce large volumes.

The first process that allowed production of significant amounts of sodium carbonate was a synthetic process known as the LeBlanc process, developed by the French chemist Nicolas LeBlanc (1742-1806). In this process, salt was reacted with sulfuric acid to produce sodium sulfate and hydrochloric acid. The sodium sulfate was heated in the presence of limestone and coal and the resulting mixture contained calcium sulfate and sodium carbonate, which was then extracted out.

Two significant problems with the LeBlanc process, high expense and significant pollution , inspired a Belgian chemical engineer named Ernest Solvay (1838-1922) to develop a better process for creating sodium carbonate. In the Solvay process, ammonia and carbon dioxide are used to produce sodium carbonate from salt and limestone. Initially, the ammonia and carbon dioxide are reacted with water to form the weak electrolytes ammonium hydroxide and carbonic acid. These ions react further and form sodium bicarbonate . Since the bicarbonate barely dissolves in water, it separates out from the solution . At this point, the sodium bicarbonate is filtered and converted into sodium carbonate by heating.

Synthetic production is not the only method of obtaining sodium carbonate. A significant amount is mined directly from naturally occurring sources. The largest natural sources for sodium carbonate in the United States are found around Green River, Wyoming, and in the dried-up desert Lake Searles in California.

Properties of sodium carbonate

At room temperature , sodium carbonate (Na2CO3) is an odorless, grayish white powder which is hygroscopic. This means when it is exposed to air, it can spontaneously absorb water molecules. Another familiar compound that has this hygroscopic quality is sugar. Sodium carbonate has a melting point of 1,564°F (851°C), a density of 2.53 g/cm3, and is soluble in water. A water solution of soda ash has a basic pH and a strong alkaline taste. When it is placed in a slightly acidic solution, it decomposes and forms bubbles. This effect, called effervescence, is found in many commercial antacid products which use sodium carbonate as an active ingredient.

Anhydrous (without water) sodium carbonate can absorb various amounts of water and form hydrates which have slightly different characteristics. When one water molecule per molecule of sodium carbonate is absorbed, the resulting substance, sodium carbonate monohydrate, is represented by the chemical formula Na2CO3 • H2O. This compound has a slightly lower density than the anhydrous version. Another common hydrate is formed by the absorption of ten water molecules per molecule of sodium carbonate. This compound, Na2CO3• 10H2O, known as sodium carbonate decahydrate, exists as transparent crystals which readily effervesce when exposed to air.

Uses of sodium carbonate

Sodium carbonate is utilized by many industries during the manufacture of different products. The most significant user is the glass industry which uses sodium carbonate to decompose silicates for glass making. The cosmetic industry uses it for manufacturing soap . The chemical industry uses it as a precursor to numerous sodium containing reagents. It is also important in photography , the textile industry, and water treatment . In addition to these industrial applications, sodium carbonate is used in medicine as an antacid.

Resources

books

Budavari, Susan, ed. The Merck Index. Rahway: Merck & Co., Inc., 1989.

Faith, W.L., Donald Keyes, and Ronald Clark. Industrial Chemicals. New York: John Wiley & Sons, 1966.

Lide, D.R., ed. CRC Handbook of Chemistry and Physics Boca Raton: CRC Press, 2001.

Perry Romanowski

KEY TERMS

Anhydrous

—A compound which does not contain any absorbed water.

Hydrate

—A compound which contains a certain amount of absorbed water.

Hygroscopic

—A compound which has a tendency to absorb water molecules.

LeBlanc process

—A method of sodium carbonate production using salt, limestone, and coal.

Soda ash

—A name for sodium carbonate which reflects its original source, the ashes of burnt seaweed.

Solvay process

—The current synthetic method of sodium carbonate production from ammonia, carbon dioxide, salt, and limestone.

sodium carbonate See soda