So we are eating something mined from the ground?
Yep, like salt.
The chemicals they put in our foods, can be used to extinguish fires.
Enjoy gentlemen.
Subject: How baking soda is made - Background, Raw materials, Quality control
[1]How Products Are Made :: [2]Volume 1
Baking Soda
Background
Baking soda is a white crystalline powder (NaHCO[3]) 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 mouth-wash 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
(Na[2]CO[3]), 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
Pharnacopoeia (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.
Raw Materials
Baking soda, or 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-square-mile
(1,554-square-kilometer) lake. As it evaporated over time, this lake
left a 200-billion-ton deposit of pure trona 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 feet (457.2 meters) below
the surface. FMC's mine shafts contain nearly 2,500 (4,022.5
kilometers) miles of tunnels and cover 24 square miles (62 square
kilometers). Fifteen feet (4.57 meters) wide and nine feet (2.74
meters) tall, these tunnels allow the necessary equipment and vehicles
to travel through them.
The Manufacturing
Process
Making soda ash
* 1 Soda ash can be manufactured chemically using the Solvay process,
or it can be made from trona ore. If trona ore is used, it must
first be mined. After it has been brought to the surface, the trona
ore is transported to a variety of processing plants. There, the
ore is refined into a slurry of sodium sesquicarbonate, an
intermediate soda ash product that actually contains both soda ash
(sodium carbonate) and baking soda (sodium bicarbonate).
Making baking soda
* 2 Next, the intermediate soda ash solution is put into a
centrifuge, which separates the liquid from the crystals. The
crystals are then dissolved in a bicarbonate solution (a soda ash
solution made by the manufacturer) in a rotary dissolver, thereby
becoming a saturated solution. This solution is filtered to remove
any non-soluble materials and is then pumped through a feed tank to
the top of a carbonating tower.
* 3 Purified carbon dioxide is introduced into the bottom of the
tower and held under pressure. As the saturated sodium solution
moves through the tower, it cools and reacts with the carbon
dioxide to form sodium bicarbonate crystals. These crystals are
collected at the bottom of the tower and transferred to another
centrifuge, where excess solution (filtrate) is filtered out. The
crystals are then washed in a bicarbonate solution, forming a
cake-like substance ready for drying. The filtrate that is removed
from the centrifuge is recycled to the rotary dissolver, where it
is used to saturate more intermediate soda ash crystals.
* 4 The washed filter cake is then dried on either a continuous belt
conveyor or in a vertical tube drier called a flash dryer. The
theoretical yield from the process, according to the Church &
Dwight Company, is between 90 and 95 percent, and the baking soda
manufactured is more than 99 percent pure.
An illustration of the baking soda manufacturing process. A key step in
the process occurs in the carbonating tower. Here, the saturated soda
ash solution moves from the top of the tower downward. As it falls, the
solution cools and reacts with carbon dioxide to form sodium
bicarbonate crystals—baking soda. After filtering, washing, and
drying, the crystals are sorted by particle size and packaged
appropriately.
An illustration of the baking soda manufacturing process. A key step in
the process occurs in the carbonating tower. Here, the saturated soda
ash solution moves from the top of the tower downward. As it falls, the
solution cools and reacts with carbon dioxide to form sodium
bicarbonate crystals--baking soda. After filtering, washing, and
drying, the crystals are sorted by particle size and packaged
appropriately.
Sorting and storing the
different grades
* 5 Next, the dried crystals of sodium bicarbonate are separated into
various grades by particle size. Standard grades of sodium
bicarbonate and special grades are manufactured to meet customers'
specific requirements, and particle size is the major determinant
of grades. Powdered #1 and fine granular #2 have a wide range of
uses in foods, chemicals, and pharmaceuticals. Granular grades #4
and #5 are found in foods and doughnuts, cleaning compounds,
pharmaceuticals, and many other products. Industrial grade sodium
bicarbonate is used in diverse applications, including oil well
drilling fluids, fire extinguishing materials, and water treatment.
* 6 Each grade goes to a holding bin wherein atmosphere, carbon
dioxide, and moisture content are controlled to "cure" the product.
Once cured, the grades are ready to be packaged and shipped.
Quality Control
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).
The Future
At the turn of the twentieth century, 53,000 tons (48,071 metric tons)
of baking soda 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 one of the
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 (CO[2]) 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.
Where To Learn More
Books
Coyle, L. Patrick, Jr. The World Encyclopedia of Food. Facts on File,
1982.
Root, Waverley and Richard de Rochemont. Eating in America: A History.
William Morrow & Co., Inc., 1976.
Periodicals and Pamphlets
Grosswirth, Marvin. "The Wonders of NaHCO[3]," Science Digest. March,
1976.
History of the Arm & Hammer Trademark. Church & Dwight Co., Inc.
Sodium Bicarbonate. FMC Corporation.
Sodium Bicarbonate--Chemical Properties, Manufacturing. Church & Dwight
Co., Inc.
--Eva Sideman
User Contributions:
[3]1
[4]Vu Yong Wui Sti
[5]Report this comment as inappropriate
Jul 25, 2007 @ 9:09 am
This is a very detailed and well planned document; however it needs a
little more to be added to it, so that students can access more
efficient and accurate information.
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