Sodium Bicarbonate
Overview
Sodium bicarbonate (SO-dee-um bye-KAR-bun-ate) is a white, odorless, crystalline solid or powder that is stable in dry air, but that slowly decomposes in moist air to form sodium carbonate. The compound's primary uses are as an additive in human and animal food products.
Key Facts
Other Names:
Bicarbonate of soda; baking soda
Formula:
NaHCO3
Elements:
Sodium, hydrogen, carbon, oxygen
Compound Type:
Acid salt (inorganic)
State:
Solid
Molecular Weight:
84.01 g/mol
Melting Point:
about 50°C (120°F); decomposes
Boiling Point:
Not applicable; decomposes
Solubility:
Soluble in water; insoluble in ethyl alcohol
Sodium bicarbonate has been used by humans for thousands of years. Ancient Egyptian documents mention the use of a sodium bicarbonate and sodium chloride solution in the mummification of the dead. For centuries, people around the world have used sodium bicarbonate as a leavening agent for baking. A leavening agent is a substance that causes dough or batter to rise. Sodium bicarbonate produces this effect because, when heated or dissolved in water, it breaks down to produce carbon dioxide (CO2) gas:
2NaHCO3 → Na2CO3 + CO2 + H2O
Since all the compounds present in this reaction are safe for human consumption, sodium bicarbonate makes an ideal leavening agent.
Commercial production of sodium bicarbonate as baking soda dates to the late 1700s. In 1846, Connecticut physician Austin Church (1799–?) and John Dwight (1819–?) of Dedham, Massachusetts, founded a company to make and sell sodium bicarbonate. They started their company in the kitchen of Dwight's home, making the product by hand and packing it in paper bags for sale to neighbors. The Church-Dwight operation grew over the years to become the largest producer of household baking soda, now sold under the name of Arm & Hammer® baking soda. The company still produces 90 percent of all the baking soda used for household purposes in the United States. Consumers use the product for cooking, cleaning, and deodorizing homes.
How It Is Made
Sodium bicarbonate is made commercially by one of two methods. In the first method, carbon dioxide gas is passed through an aqueous solution of sodium carbonate (Na2CO3):
Na2CO3 + CO2 + H2O → 2NaHCO3
Since the bicarbonate is less soluble than the carbonate, it precipitates out of solution and can be removed by filtration.
Sodium bicarbonate is also obtained as a byproduct of the Solvay process. The Solvay process was invented in the late 1850s by Belgian chemist Ernest Solvay (1838–1922) primarily as a way of making sodium carbonate. Sodium carbonate had long been a very important industrial chemical for which no relatively inexpensive method of preparation existed. Solvay developed a procedure by which sodium chloride is treated with carbon dioxide and ammonia, resulting in the formation of sodium bicarbonate and ammonium bicarbonate. The sodium bicarbonate is then heated to obtain sodium carbonate. Although sodium carbonate is the desired product in this reaction, sodium bicarbonate can also be obtained by deleting the final step by which it is converted into sodium carbonate.
Interesting Facts
- Sodium bicarbonate is a very effective cleaning agent for certain materials. In the 1980s, restorers used an aqueous solution of the compound to clean the Statue of Liberty.
Common Uses and Potential Hazards
An estimated 560,000 metric tons (615,000 short tons) of sodium bicarbonate were consumed in the United States in 2003. About one-third of that amount was used by the food products industry, primarily in the manufacture of baking soda (pure sodium bicarbonate) and baking powder (a mixture of sodium bicarbonate and at least one other compound). Baking powder differs from baking soda in that it includes an acidic compound that reacts with sodium bicarbonate to produce carbon dioxide. One of the most common compounds mixed with sodium bicarbonate in baking powder is tartaric acid (HOOC(CHOH)2COOH), or its salt, potassium bitartrate (HOOC(CHOH)2COOK). Baking powder is a more efficient leavening agent in baking than is baking soda by itself. Baking soda is also used as an additive in foods and drinks to provide effervescence (a bubbling, fizzing, or sparkling effect) or to maintain an acidic environment in the food. The acidity provides a sharp taste and helps to preserve a food.
The second largest use of sodium bicarbonate is as an additive in animal feed. As with human foods, it maintains the proper acidity of an animal's feed, improving its ability to digest and absorb its food.
Sodium bicarbonate is also used in a number of pharmaceutical applications. For example, it is a common ingredient in antacids, products designed to relieve heartburn, acid indigestion, sour stomach, and other discomforts caused by overeating or improper foods. Some pharmaceuticals, such as Alka-Seltzer®, contain a combination of citric acid and sodium bicarbonate. The citric acid helps the sodium bicarbonate dissolve more quickly and produces more effervescence when the tablet is dissolved in water.
Sodium bicarbonate is also used in cleaning products on both a household and industrial level. Many householders use commercial baking soda, such as that sold by the Arm & Hammer company, to clean kitchen and bathroom appliances, such as sinks, stoves, and toilet bowls. Industries also use sodium bicarbonate filters to remove sulfur dioxide and other pollutants in flu gases released from factory smokestacks. The compound is also used in the treatment of wastewater to maintain proper acidity, remove certain odors (such as those of sulfur dioxide), and destroy bacteria. Some communities have used aqueous solutions of sodium bicarbonate sprayed at high pressure to remove graffiti; paint; soot and smoke residues; and mold from buildings, walls, and other public structures.
Some other applications of sodium bicarbonate include:
- As a component of fire extinguishers; when it comes into contact with an acid in the fire extinguisher, the sodium bicarbonate releases carbon dioxide and a flow of water under pressure to fight the fire;
- As a blowing agent in the preparation of plastics; blowing agents are substances that produce large volumes of gas that convert a molten product into a foamy product;
- In the manufacture of other sodium compounds;
- For gold and platinum plating; and
- To prevent the growth of mold on timber.
Sodium bicarbonate is considered safe when handled or ingested in reasonable amounts. As with any chemical, however, excessive amounts of the compound can have harmful effects. When ingested in large amounts, sodium bicarbonate can cause stomach cramps, gas, upset stomach, vomiting, frequent urination, loss of appetite, and blood in the urine and stools.
Words to Know
A solution that consists of some material dissolved in water. A solid material that settles out of a solution, often as the result of a chemical reaction.For Further Information
"Pure Baking Soda." Arm & Hammerz®. http://www.armhammer.com/ (accessed on November 8, 2005).
Snyder, C. H. The Extraordinary Chemistry of Ordinary Things, 4th ed. New York: John Wiley and Sons, 2002.
"Sodium Bicarbonate." Chemical Land 21. http://www.chemicalland21.com/arokorhi/industrialchem/inorganic/SODIUM%20BICARBONATE.htm (accessed on November 8, 2005).
"Sodium Bicarbonate." DC Chemical Co., Ltd. http://www.dcchem.co.kr/english/product/p_basic/p_basic02.htm (accessed on November 8, 2005).
See Also
Carbon Dioxide; Citric Acid; Sodium Carbonate
This is the complete article, containing 1,102 words
(approx. 4 pages at 300 words per page).
