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

AQUEOUS SOLUTION

A solution that consists of some material dissolved in water.

PRECIPITATE

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 AlsoCarbon Dioxide; Citric Acid; Sodium Carbonate

Sodium Bicarbonate

Use in antacids

Use in fighting fires

Use in baking

Resources

Sodium bicarbonate (NaHCO₃), also known as baking soda, bread soda, sodium hydrogen carbonate, bicarbonate of soda, and sodium bicarb, is a white powder that readily dissolves in water to produce sodium (Na⁺) ions and bicarbonate (HCO₃) ions. In the presence of acids, these ions create carbon dioxide gas (CO₂) and water. Baking soda, a weak base, is used in antacids, fire extinguishers, and baking powder. In almost all of its common uses, sodium bicarbonate is employed to produce carbon dioxide gas.

Use in antacids

Many commercial preparations of antacids contain sodium bicarbonate. Alka-Seltzer^® antacid contains sodium bicarbonate in addition to citric acid (C₆H₈O₇), which is used to dissolve the sodium bicarbonate. Pure baking soda will also relieve heartburn, but the citric acid in commercial antacids improves the taste and accelerates the disintegration of the tablet. When sodium bicarbonate is dissolved in water, the compound separates into ions, or charged particles, of sodium (Na⁺) and bicarbonate (HCO₃). The bicarbonate ions then react with acids as shown below. The symbol (aq), meaning aqueous, shows that the substance is dissolved in water; the symbol (g) refers to a gas, and (l) means a liquid. The hydrogen ions (H⁺) are from acids.

H⁺(aq) + HCO₃^- → H₂CO₃ (aq) → H₂O (1) + CO₂(g).

As shown above, one hydrogen ion and one bicarbonate ion react to produce a molecule of liquid water and a molecule of carbon dioxide gas. This can be demonstrated at home by filling a recloseable plastic bag with one ounce (30 ml) of vinegar. The vinegar represents stomach acid. A teaspoon (5 ml) of baking soda (or an Alka-Seltzer^® tablet) is then dropped in the bag and the bag is quickly closed. The fizzing is caused by the production of carbon dioxide gas. The bag will quickly fill up with gas, demonstrating why many people burp after taking an antacid. This belching helps relieve the pressure that builds up in the stomach. In spite of its widespread use, sodium bicarbonate can be harmful in large doses by disrupting the levels of sodium ions in the bloodstream. In a few rare cases, some people have consumed such large amounts of sodium bicarbonate that their stomachs were damaged by the internal pressure that built up from the carbon dioxide gas.

Use in fighting fires

When sodium bicarbonate is heated above 518°F (270°C) it decomposes and produces carbon dioxide. Since carbon dioxide gas is more dense than air, it tends to sink; thus carbon dioxide can smother a fire by obstructing the flow of oxygen to the fuel, which needs oxygen to continue burning. Sodium bicarbonate is employed in fire extinguishers and is widely used on electrical fires.

Use in baking

Baking powder consists of sodium bicarbonate mixed with a weak acid. In much the same manner as

KEY TERMS

Antacid —A basic (alkaline) chemical that relieves the effects of excess stomach acids.

Aqueous —A solution dissolved in water; salt water could be called aqueous salt.

Ion —An atom or molecule that has acquired electrical charge by either losing electrons (positively charged ion) or gaining electrons (negatively charged ion).

citric acid produces carbon dioxide gas in some antacids, the weak acid in baking powder—often potassium hydrogen tartrate (KHC₄H₄O₆)—provides a source of hydrogen ions; the ions react with the sodium bicarbonate to produce carbon dioxide gas, which makes dough and batter rise. Baking powder is often used as a source of carbon dioxide in baking instead of yeast, since yeast produces a distinct taste that is not desirable in all foods, such as cakes.

See also Acids and bases.

Resources

BOOKS

Branen, Larry, et al. Food Additives. New York: Marcel Dekker, 2002.

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

Francis, Frederick John. Wiley Encyclopedia of Food Science and Technology. New York: Wiley, 2000.

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

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.

PERIODICALS

Campbell, Hannah. “The Baker’s Friend: How America’s Best Brand of Baking Soda Was Born.” Country Living, vol. 12, March 1989.

Louis Gotlib

Sodium bicarbonate

Sodium bicarbonate (NaHCO3), also known as baking soda or sodium hydrogen carbonate, is a white powder that readily dissolves in water to produce sodium (Na+) ions and bicarbonate (HCO3) ions. In the presence of acids, these ions create carbon dioxide gas (CO2) and water. Baking soda, a weak base, is used in antacids, fire extinguishers, and baking powder. In almost all of its common uses, sodium bicarbonate is employed to produce carbon dioxide gas.

Use in antacids

Many commercial preparations of antacids contain sodium bicarbonate. Alka-Seltzer antacid contains sodium bicarbonate in addition to citric acid (C6H8O7), which is used to dissolve the sodium bicarbonate. Pure baking soda will also relieve heartburn, but the citric acid in commercial antacids improves the taste and accelerates the disintegration of the tablet. When sodium bicarbonate is dissolved in water, the compound separates into ions, or charged particles, of sodium (Na+) and bicarbonate (HCO3). The bicarbonate ions then react with acids as shown below. The symbol (aq), meaning aqueous, shows that the substance is dissolved in water; the symbol (g) refers to a gas, and (l) means a liquid. The hydrogen ions (H+) are from acids.

As shown above, one hydrogen ion and one bicarbonate ion react to produce a molecule of water and a molecule of carbon dioxide gas. This can be demonstrated at home by filling a reclosable plastic bag with one ounce (30 ml) of vinegar. The vinegar represents stomach acid. A teaspoon (5 ml) of baking soda (or an Alka-Seltzer tablet) is then dropped in the bag and the bag is quickly closed. The fizzing is caused by the production of carbon dioxide gas. The bag will quickly fill up with gas, demonstrating why many people burp after taking an antacid. This belching helps relieve the pressure that builds up in the stomach. In spite of its widespread use, sodium bicarbonate can be harmful in large doses by disrupting the levels of sodium ions in the bloodstream. In a few rare cases, some people have consumed such large amounts of sodium bicarbonate that their stomachs were damaged by the internal pressure that built up from the carbon dioxide gas.

Use in fighting fires

When sodium bicarbonate is heated above 518°F (270°C) it decomposes and produces carbon dioxide. Since carbon dioxide gas is more dense than air, it tends to sink; thus carbon dioxide can smother a fire by obstructing the flow of oxygen to the fuel, which needs oxygen to continue burning. Sodium bicarbonate is employed in fire extinguishers and is widely used on electrical fires.

Use in baking

Baking powder consists of sodium bicarbonate mixed with a weak acid. In much the same manner as citric acid produces carbon dioxide gas in some antacids, the weak acid in baking powder—often potassium hydrogen tartrate (KHC4H4O6)—provides a source of hydrogen ions; the ions react with the sodium bicarbonate to produce carbon dioxide gas, which makes dough and batter rise. Baking powder is often used as a source of carbon dioxide in baking instead of yeast , since yeast produces a distinct taste that is not desirable in all foods, such as cakes.

See also Acids and bases.

Resources

books

Francis, Frederick. Wiley Encyclopedia of Food Science and Technology. New York: Wiley, 1999.

Lewis, Richard L. Food Additives Handbook. New York: Van Nostrand Reinhold, 1989.

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

periodicals

Campbell, Hannah. "The Baker's Friend: How America's Best Brand of Baking Soda Was Born." Country Living vol. 12, March 1989.

Norton, Clark. "Facts on Fizz; Bubbly or Creamy, Calcium or Aluminum? Here's How to Choose a Heartburn Remedy." Health vol. 5, July/August 1991.

"Stomach Acid-An Old Remedy." Consumer Reports vol. 59, February 1994.

Louis Gotlib

KEY TERMS

Antacid

—A basic (alkaline) chemical that relieves the effects of excess stomach acids.

Aqueous

—A solution dissolved in water; salt water could be called aqueous salt.

Ion

—An atom or molecule which has acquired electrical charge by either losing electrons (positively charged ion) or gaining electrons (negatively charged ion).

sodium bicarbonate Also known as baking soda or bicarbonate of soda (chemically NaHCO₃), liberates carbon dioxide when in contact with acid. Used as a raising agent in baking flour confectionery. See also baking powder.

A small pinch of sodium bicarbonate preserves the green colour in cooked vegetables (too much destroys the vitamin C). Also helps to reduce acidity when stewing sour plums or rhubarb.

so·di·um bi·car·bon·ate • n. a soluble white powder, NaHCO₃, used in fire extinguishers and effervescent drinks and as a leavening agent in baking. Also called baking soda.