Baking soda is a white crystalline powder (NaHCO3) better known to chemists as sodium bicarbonate, bicarbonate of soda, sodium hydrogen carbonate, or sodium acid carbonate. It is classified as an acid salt, formed by combining an acid (carbonic) and a base (sodium hydroxide), and it reacts with other chemicals as a mild alkali. At temperatures above 300 degrees Fahrenheit (149 degrees Celsius), baking soda decomposes into sodium carbonate (a more stable substance), water, and carbon dioxide.
The native chemical and physical properties of baking soda account for its wide range of applications, including cleaning, deodorizing, buffering, and fire extinguishing. Baking soda neutralizes odors chemically, rather than masking or absorbing them. Consequently, it is used in bath salts and deodorant body powders. Baking soda tends to maintain a pH of 8.1 (7 is neutral) even when acids, which lower pH, or bases, which raise pH, are added to the solution. Its ability to tabletize makes it a good effervescent ingredient in antacids and denture cleaning products. Sodium bicarbonate is also found in some anti-plaque mouthwash products and toothpaste. When baking soda is used as a cleaner in paste form or dry on a damp sponge, its crystalline structure provides a gentle abrasion that helps to remove dirt without scratching sensitive surfaces. Its mild alkalinity works to turn up fatty acids contained in dirt and grease into a form of soap that can be dissolved in water and rinsed easily. Baking soda is also used as a leavening agent in making baked goods such as bread or pancakes. When combined with an acidic agent (such as lemon juice), carbon dioxide gas is released and is absorbed by the product's cells. As the gas expands during baking, the cell walls expand as well, creating a leavened product.
In addition to its many home uses, baking soda also has many industrial applications. For instance, baking soda releases carbon dioxide when heated. Since carbon dioxide is heavier than air, it can smother flames by keeping oxygen out, making sodium bicarbonate a useful agent in fire extinguishers. Other applications include air pollution control (because it absorbs sulfur dioxide and other acid gas emissions), abrasive blastings for removal of surface coatings, chemical manufacturing, leather tanning, oil well drilling fluids (because it precipitates calcium and acts as a lubricant), rubber and plastic manufacturing, paper manufacturing, textile processing, and water treatment (because it reduces the level of lead and other heavy metals).
Imported from England, baking soda was first used in America during colonial times, but it was not produced in the United States until 1839. In 1846, Austin Church, a Connecticut physician, and John Dwight, a farmer from Massachusetts, established a factory in New York to manufacture baking soda. Dr. Church's son, John, owned a mill called the Vulcan Spice Mills. Vulcan, the Roman god of forge and fire, was represented by an arm and hammer, and the new baking soda company adopted the arm and hammer logo as its own. Today, the Arm & Hammer brand of baking soda is among the most widely recognized brand names.
Named after Nicolas Leblanc, the French chemist who invented it, the Leblanc process was the earliest means of manufacturing soda ash (Na2C03), from which sodium bicarbonate is made. Sodium chloride (table salt) was heated with sulfuric acid, producing sodium sulfate and hydrochloric acid. The sodium sulfate was then heated with coal and limestone to form sodium carbonate, or soda ash.
In the late 1800s, another method of producing soda ash was devised by Ernest Solvay, a Belgian chemical engineer. The Solvay method was soon adapted in the United States, where it replaced the Leblanc process. In the Solvay process, carbon dioxide and ammonia are passed into a concentrated solution of sodium chloride. Crude sodium bicarbonate precipitates out and is heated to form soda ash, which is then further treated and refined to form sodium bicarbonate of United States Pharmacopoeia (U.S.P.) purity.
Although this method of producing baking soda ash is widely used, it is also problematic because the chemicals used in the process are pollutants and cause disposal problems. An alternative is to refine soda ash from trona ore, a natural deposit.
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