Sodium bicarbonate (IUPAC name: sodium hydrogen carbonate) is a chemical compound with the formula NaHCO3. It is a salt composed of sodium ions and bicarbonate ions. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate). The natural mineral form is nahcolite. It is a component of the mineral natron and is found dissolved in many mineral springs. It is among the food additives encoded by the European Union, identified as E 500.
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Nomenclature
Since it has long been known and is widely used, the salt has many related names such as baking soda, bread soda, cooking soda, and bicarbonate of soda. In colloquial usage, the names sodium bicarbonate and bicarbonate of soda are often truncated. Forms such as sodium bicarb, bicarb soda, bicarbonate, bicarb, or even bica are common. The word saleratus, from Latin sal æratus meaning "aerated salt", was widely used in the 19th century for both sodium bicarbonate and potassium bicarbonate.
The prefix, bi, in bicarbonate comes from an outdated naming system and is based on the observation that there is twice as much carbonate (CO3) per sodium in sodium bicarbonate (NaHCO3) as there is carbonate per sodium in sodium carbonate (Na2CO3) and other carbonates. The modern way of analyzing the situation based on the exact chemical composition (which was unknown when the name sodium bicarbonate was coined) says this the other way around: there is half as much sodium in NaHCO3 as in Na2CO3 (Na versus Na2).
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Uses
Sodium bicarbonate has a wide variety of uses.
Cooking
Sodium bicarbonate, referred to as baking soda, is primarily used in baking, as a leavening agent. It reacts with acidic components in batters, releasing carbon dioxide, which causes expansion of the batter and forms the characteristic texture and grain in pancakes, cakes, quick breads, soda bread, and other baked and fried foods. Acidic compounds that induce this reaction include phosphates, cream of tartar, lemon juice, yogurt, buttermilk, cocoa and vinegar. Natural acids in sourdough can be leavened with the addition of small amounts as well.
Heat can also independently cause sodium bicarbonate to act as a raising agent by releasing carbon dioxide when used in baking. When used on its own, only half the available CO2 is released. Additionally, without an acid added to baking soda, sodium carbonate is produced that is strongly alkaline and gives the baked product a bitter, "soapy" taste and a yellow color. Baking powder differs in that it includes an acid which is activated by the addition of water. Carbon dioxide production from exposure to heat starts at temperatures above 80 °C.
Since the reaction occurs slowly at room temperature, mixtures (cake batter, etc.) can be allowed to stand without rising until they are heated in the oven.
Many forms of baking powder will contain sodium bicarbonate combined with calcium acid phosphate, sodium aluminium phosphate or cream of tartar. Sodium bicarbonate was sometimes used in cooking vegetables, to make them softer, although this has gone out of fashion, as most people now prefer firmer vegetables. However, it is still used in Asian and Latin American cuisine to tenderise meats. Baking soda may react with acids in food, including vitamin C (L-ascorbic acid). It is also used in breading such as for fried foods to enhance crispness and allow passages for steam to escape, so the breading is not blown off during cooking.
Pest control
Sodium bicarbonate can be used to kill cockroaches. Once consumed, it causes internal organs of cockroaches to burst due to gas collection.
Sodium bicarbonate can be an effective way of controlling fungal growth, and in the United States is registered by the Environmental Protection Agency as a biopesticide.
Paint and corrosion removal
Sodium bicarbonate is used in a process for removing paint and corrosion called sodablasting; the process is particularly suitable for cleaning aluminium panels which can be distorted by other types of abrasive.
Alkalinity/pH increase
Sodium bicarbonate can be administered to pools, spas, and garden ponds to raise the total alkalinity. This will also raise the pH level and make maintaining proper pH easier. In the event that the pH is low and the alkalinity is adequate or high, sodium bicarbonate should not be used to adjust the pH.
Pyrotechnics
Sodium bicarbonate is one of the main components of the common incendiary "black snake" firework. The effect is caused by the thermal decomposition, which produces carbon dioxide gas to produce a long snake-like ash as a combustion product of the other main component, sucrose.
Mild disinfectant
It has weak disinfectant properties, and it may be an effective fungicide against some organisms. Because baking soda will absorb musty smells, it has become a reliable method for used-book sellers when making books less malodorous.
Fire extinguisher
Sodium bicarbonate can be used to extinguish small grease or electrical fires by being thrown over the fire, as heating of sodium bicarbonate releases carbon dioxide. However, it should not be applied to fires in deep fryers; the sudden release of gas may cause the grease to splatter. Sodium bicarbonate is used in BC dry chemical fire extinguishers as an alternative to the more corrosive diammonium phosphate in ABC extinguishers. The alkaline nature of sodium bicarbonate makes it the only dry chemical agent, besides Purple-K, that was used in large-scale fire suppression systems installed in commercial kitchens. Because it can act as an alkali, the agent has a mild saponification effect on hot grease, which forms a smothering, soapy foam.
Neutralisation of acids and bases
Sodium bicarbonate is amphoteric, reacting with acids and bases. It reacts violently with acids, releasing CO2 gas as a reaction product. It is commonly used to neutralize unwanted acid solutions or acid spills in chemical laboratories.
A wide variety of applications follows from its neutralisation properties, including reducing the spread of white phosphorus from incendiary bullets inside an afflicted soldier's wounds.
Medical uses
Sodium bicarbonate mixed with water can be used as an antacid to treat acid indigestion and heartburn. Its reaction with stomach acid produces salt, water, and carbon dioxide:
Intravenous sodium bicarbonate is an aqueous solution that is sometimes used for cases of acidosis, or when insufficient sodium or bicarbonate ions are in the blood. In cases of respiratory acidosis, the infused bicarbonate ion drives the carbonic acid/bicarbonate buffer of plasma to the left and, thus, raises the pH. It is for this reason that sodium bicarbonate is used in medically supervised cardiopulmonary resuscitation. Infusion of bicarbonate is indicated only when the blood pH is markedly (<7.1-7.0) low.
It is used for treatment of hyperkalemia, as it will drive K+ back into cells during periods of acidosis. Since sodium bicarbonate can cause alkalosis, it is sometimes used to treat aspirin overdoses. Aspirin requires an acidic environment for proper absorption, and the basic environment diminishes aspirin absorption in the case of an overdose. Sodium bicarbonate has also been used in the treatment of tricyclic antidepressant overdose. It can also be applied topically as a paste, with three parts baking soda to one part water, to relieve some kinds of insect bites and stings (as well as accompanying swelling).
Sodium bicarbonate has been found to have no effect on the blood pressure of several types of rat models susceptible to salt-sensitive hypertension, in contrast with sodium chloride. This was ascribed to the high concentration of chloride, rather than the sodium content in dietary salts.
Sodium bicarbonate can be used to treat an allergic reaction to plants such as poison ivy, poison oak, or poison sumac to relieve some of the associated itching.
Bicarbonate of soda can also be useful in removing splinters from the skin.
Some alternative practitioners, such as Tullio Simoncini, have promoted baking soda as a cancer cure, which the American Cancer Society has warned against due to both its unproven effectiveness and potential danger in use.
Sodium bicarbonate can be added to local anaesthetics, to speed up the onset of their effects and make their injection less painful. It is also a component of Moffett's solution, used in nasal surgery.
Personal hygiene
Toothpaste containing sodium bicarbonate has in several studies been shown to have a better whitening and plaque removal effect than toothpastes without it.
Sodium bicarbonate is also used as an ingredient in some mouthwashes. It has anticaries and abrasive properties. It works as a mechanical cleanser on the teeth and gums, neutralises the production of acid in the mouth, and also acts as an antiseptic to help prevent infections.
Sodium bicarbonate in combination with other ingredients can be used to make a dry or wet deodorant.
Sodium bicarbonate may be used as a buffering agent, combined with table salt, when creating a solution for nasal irrigation.
It is used in eye hygiene to treat blepharitis. This is done by addition of a teaspoon of sodium bicarbonate to cool water that was recently boiled, followed by gentle scrubbing of the eyelash base with a cotton swab dipped in the solution.
In sports
Small amounts of sodium bicarbonate have been shown to be useful as a supplement for athletes in speed-based events, such as middle-distance running, lasting from about one to seven minutes. However, overdose is a serious risk because sodium bicarbonate is slightly toxic; and gastrointestinal irritation is of particular concern. Additionally, this practice causes a significant increase in dietary sodium.
As a cleaning agent
A paste from baking soda can be very effective when used in cleaning and scrubbing. For cleaning aluminium objects, the use of sodium bicarbonate is discouraged, as it attacks the thin unreactive protective oxide layer of this otherwise very reactive metal. A solution in warm water will remove the tarnish from silver when the silver is in contact with a piece of aluminium foil. A paste of sodium bicarbonate and water is useful in removing surface rust as the rust forms a water-soluble compound when in a concentrated alkaline solution. Cold water should be used, as hot water solutions can corrode steel. Baking soda is commonly added to washing machines as a replacement for softener and to remove odors from clothes. Sodium bicarbonate is also effective in removing heavy tea and coffee stains from cups when diluted with warm water. Also, baking soda can be used as an ultimate multi purpose odor remover.
During the Manhattan Project to develop the nuclear bomb in the early 1940s, many scientists investigated the toxic properties of uranium. They found that uranium oxides stick very well to cotton cloth, but did not wash out with soap or laundry detergent. The uranium would wash out with a 2% solution of sodium bicarbonate (baking soda). Clothing can become contaminated with depleted uranium (DU) dust, and then normal laundering will not remove it. Those at risk of DU dust exposure should have their clothing washed with about 6 ounces (170 g) of baking soda in 2 gallons (7.5 l) of water.
Cattle feed supplements
Sodium bicarbonate is sold as a cattle feed supplement, in particular as a buffering agent for the rumen.
Chemistry
Sodium bicarbonate is an amphoteric compound. Aqueous solutions are very mildly alkaline due to the formation of carbonic acid and hydroxide ion:
Sodium bicarbonate can be used as a wash to remove any acidic impurities from a "crude" liquid, producing a purer sample. Reaction of sodium bicarbonate and an acid produce a salt and carbonic acid, which readily decomposes to carbon dioxide and water:
Sodium bicarbonate reacts with acetic acid (found in vinegar), producing sodium acetate, water, and carbon dioxide:
Sodium bicarbonate reacts with bases such as sodium hydroxide to form carbonates:
Sodium bicarbonate reacts with carboxyl groups in proteins to give a brisk effervescence from the formation of CO
2. This reaction is used to test for the presence of carboxylic groups in protein.
Thermal decomposition
Above 50 °C, sodium bicarbonate gradually decomposes into sodium carbonate, water and carbon dioxide. The conversion is fast at 200 °C:
Most bicarbonates undergo this dehydration reaction. Further heating converts the carbonate into the oxide (above 850 °C):
These conversions are relevant to the use of NaHCO3 as a fire-suppression agent ("BC powder") in some dry powder fire extinguishers.
History
In 1791, a French chemist, Nicolas Leblanc, produced sodium carbonate, also known as soda ash. In 1846, two New York bakers, John Dwight and Austin Church, established the first factory in the United States to develop baking soda from sodium carbonate and carbon dioxide.
This compound, referred to as saleratus, is mentioned in the novel Captains Courageous by Rudyard Kipling as being used extensively in the 1800s in commercial fishing to prevent freshly caught fish from spoiling.
Production
NaHCO3 is mainly prepared by the Solvay process, which is the reaction of sodium chloride, ammonia, and carbon dioxide in water. Calcium carbonate is used as the source of CO2 and the resultant calcium oxide is used to recover the ammonia from the ammonium chloride. The product shows a low purity (75%). Pure product is obtained from sodium carbonate, water, and carbon dioxide as reported in one of the following reactions. It is produced on the scale of about 100,000 tonnes/year (as of 2001).
NaHCO3 may be obtained by the reaction of carbon dioxide with an aqueous solution of sodium hydroxide. The initial reaction produces sodium carbonate:
Further addition of carbon dioxide produces sodium bicarbonate, which at sufficiently high concentration will precipitate out of solution:
Commercial quantities of baking soda are also produced by a similar method: soda ash, mined in the form of the ore trona, is dissolved in water and treated with carbon dioxide. Sodium bicarbonate precipitates as a solid from this method:
Mining
Naturally occurring deposits of nahcolite (NaHCO3) are found in the Eocene-age (55.8-33.9 Mya) Green River Formation, Piceance Basin in Colorado. Nahcolite was deposited as beds during periods of high evaporation in the basin. It is commercially mined using common underground mining techniques such as bore, drum, and longwall mining in a fashion very similar to coal mining. A very small portion is also obtained using in situ leach techniques involving dissolution of the nahcolite by heated water pumped through the nahcolite beds that have previously been mined using the aforementioned techniques. It is then reconstituted through a natural cooling crystallisation process. Currently only Tronox (formerly FMC) in the Green River Wyoming basin has successfully commercially solution mined the product.
Popular culture
Film
Sodium bicarbonate, as "bicarbonate of soda", was a frequent source of punch lines for Groucho Marx in Marx brothers movies. In Duck Soup, Marx plays the leader of a nation at war. In one scene, he receives a message from the battlefield that his general is reporting a gas attack, and Groucho tells his aide: "Tell him to take a teaspoonful of bicarbonate of soda and a half a glass of water." In A Night at the Opera, Groucho's character addresses the opening night crowd at an opera by saying of the lead tenor: "Signor Lassparri comes from a very famous family. His mother was a well-known bass singer. His father was the first man to stuff spaghetti with bicarbonate of soda, thus causing and curing indigestion at the same time."
Difference between baking soda and baking powder
Baking soda is a pure substance (bicarbonate of soda). In the UK, Baking powder is traditionally a mixture of bicarbonate of soda and cream of tartar (from tartaric acid).
Baking soda is alkaline, so acid is used in baking powder to avoid a metallic taste when the chemical change during baking creates sodium carbonate. However, to avoid the over-flavouring of acidic taste, non-acid ingredients such as whole milk or Dutch-processed cocoa must be added.
Source of the article : Wikipedia
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