Sodium bicarbonate (NaHCO3) is a white crystalline powder commonly known to as baking soda. It is classified as an acid salt, formed by combining an acid (carbonic) and abase (sodium hydroxide), and it reacts with other chemicals as a mild alkali. At temperatures above 300°F (149°C), sodium bicarbonate decomposes into sodium carbonate (a more stable substance), water, and carbon dioxide.
The native chemical and physical properties of sodium bicarbonate account for its wide range of applications, including cleaning, deodorizing, buffering, and fire extinguishing. Sodium bicarbonate neutralizes odors chemically, rather than masking or absorbing them. Consequently, it is used in bath salts and deodorant body powders. Sodium bicarbonate 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 sodium bicarbonate 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. Sodium bicarbonate 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, sodium bicarbonate also has many industrial applications. For instance, sodium bicarbonate 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 asa 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, sodium bicarbonate was first used in America during colonial times, but it was not produced in the United States until 1839. In1846, Austin Church, a Connecticut physician, and John Dwight, a farmer from Massachusetts, established a factory in New York to manufacture sodium bicarbonate. 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 sodium bicarbonate 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 sodium bicarbonate 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 tronaore, a natural deposit.
Sodium bicarbonate, comes from soda ash obtained either through the Solvay process or from trona ore, a hard, crystalline material. Trona dates back 50 million years, to when the land surrounding Green River, Wyoming, was covered by a 600 sq mi (1,554 sq km) lake. As it evaporated over time, this lake left a 200-billion-ton deposit of puretrona between layers of sandstone and shale. The deposit at the Green River Basin is large enough to meet the entire world's needs for soda ash and sodium bicarbonate for thousands of years.
Because the synthetic process used in the Solvay method presented some pollution problems, Church & Dwight Co. Inc. is basing more and more of its manufacturing on trona mining. Another large producer of soda ash, the FMC Corporation, also relies on trona to manufacture soda ash and sodium bicarbonate. Trona is mined at 1,500 ft (457.2 m) below the surface. FMC's mine shafts contain nearly 2,500 mi (4,022.5 km) of tunnels and cover 24 sq mi (62 sq km). Fifteen feett (4.57) wide and 9 ft (2.74 m) tall, these tunnels allow the necessary equipment and vehicles to travel through them.
The quality of sodium bicarbonate is controlled at every stage of the manufacturing process. Materials, equipment, and the process itself are selected to yield sodium bicarbonate of the highest possible quality. According to FMC sources, when the company constructed plants, it chose materials and equipment that would be compatible with the stringent quality requirements for making pharmaceutical grade sodium bicarbonate. FMC also uses Statistical Process Control (SPC) to maintain unvarying daily quality, and key operating parameters are charted to maintain process control. Product quality parameters are recorded by lot number, and samples are kept for two to three years.
All U.S.P. grades meet the United States Pharmacopoeia and Food Chemicals Codex specifications for use in pharmaceutical and food applications. In addition, food grade sodium bicarbonate meets the requirements specified by the U.S. Food and Drug Administration as a substance that is Generally Recognized as Safe (GRAS).
At the turn of the twentieth century, 53,000 tons (48,071 metric tons) of sodium bicarbonate were sold annually. While the population increased dramatically, sales by 1990 were down to about 32,000 tons (29,024 metric tons) per year. Self-rising flour and cake and biscuit mixes have decreased the demand for baking soda as an important baking ingredient. Nevertheless, demand for the product is still significant. Commercial bakers (particularly cookie manufacturers) are major users of this product. One of the most important attributes of sodium bicarbonate is that, when exposed to heat, it releases carbon dioxide gas (CO2) which makes the baking goods rise. Sodium bicarbonate is also used in the pharmaceutical and health industries, and it has other industrial applications as well. It therefore continues to be an important product for today and for the future.
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