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Sodium bicarbonate
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Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula NaHCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slight alkaline taste resembling that of washing soda (sodium carbonate). It is a component of the mineral natron and is found dissolved in many mineral springs. The natural mineral form is known as nahcolite. It is also produced artificially.
Since it has long been known and is widely used, the salt has many related names such as baking soda, bread soda, cooking soda, bicarbonate of soda.
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Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula NaHCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slight alkaline taste resembling that of washing soda (sodium carbonate). It is a component of the mineral natron and is found dissolved in many mineral springs. The natural mineral form is known as nahcolite. It is also produced artificially.
Since it has long been known and is widely used, the salt has many related names such as baking soda, bread soda, cooking soda, bicarbonate of soda. Colloquially, its name is shortened to sodium bicarb, bicarb soda, or quite simple, bicarb. 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 term has now fallen out of common usage.
History
The ancient Egyptians used natural deposits of natron, a mixture consisting mostly of sodium carbonate decahydrate and sodium bicarbonate. The natron was used as a cleansing agent like soap.
In 1791, a French chemist produced sodium bicarbonate as we know it today. But it was only in 1846 that two New York bakers, John Dwight and Austin Church, developed the process of making baking soda from sodium carbonate and carbon dioxide.
Production
NaHCO3 is mainly prepared by the Solvay process, which is the reaction of calcium carbonate, sodium chloride, ammonia, and carbon dioxide in water. It is produced on the scale of about 100,000 ton/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:
- CO2 + 2NaOH ? Na2CO3 + H2O
Further addition of carbon dioxide produces sodium bicarbonate, which at sufficiently high concentration will precipitate out of solution:
- Na2CO3 + CO2 + H2O ? 2NaHCO3
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:
- Na2CO3 + CO2 + H2O ? 2NaHCO3
Mining
Naturally occurring deposits of nahcolite (NaHCO3) are found in the Eocene-age (55.8 ± 0.2 - 33.9 ± 0.1 Ma) Green River Formation, Piceance Creek Basin in Colorado. Nahcolite was deposited as beds during periods of high evaporation in the basin. It is commercially mined using in-situ leach techniques involving dissolution of the nahcolite by heated water which is pumped through the nahcolite beds and reconstituted through a natural cooling crystallization process. , the only North American processor of natural sodium bicarbonate is owned by AmerAlia (AALA) and The Sentient Group. The operation is located 54 miles northwest of Rifle, Colorado. The Natural Soda facility has changed ownership several times over the last decade, proving difficult to turn a profit. All other North American producers base their production of sodium bicarbonate on trona found in the Green River Formation of Wyoming.
Chemistry
Sodium bicarbonate is an amphoteric compound. Aqueous solutions are mildly alkaline:
- HCO3- + H2O ? H2CO3 + OH-
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 to give a salt and carbonic acid, which readily decomposes to carbon dioxide and water:
- NaHCO3 + HCl ? NaCl + H2CO3
- H2CO3 ? H2O + CO2 (gas)
Reaction of sodium bicarbonate and acetic acid:
- NaHCO3 + CH3COOH ? CH3COONa + H2O + CO2 (gas)
Sodium bicarbonate reacts with bases:
- NaHCO3 + NaOH ? Na2CO3 + H2O
Thermal decomposition
Above 70 °C, it gradually decomposes into sodium carbonate, water and carbon dioxide. The conversion is fast at 250 °C:
- 2NaHCO3 ? Na2CO3 + H2O + CO2
Most bicarbonates undergo this dehydration reaction. Further heating converts the carbonate into the oxide (at around 1000 °C):
- Na2CO3 ? Na2O + CO2
These conversions are relevant to the use of NaHCO3 as a fire-suppression agent ("BC powder") in some dry powder fire extinguishers.
Applications
Cooking
Sodium bicarbonate is primarily used in cooking (baking) where it reacts with other components to release carbon dioxide, that helps dough "rise". The acidic compounds that induce this reaction include phosphates, cream of tartar, lemon juice, yogurt, buttermilk, cocoa, vinegar, etc. Sodium bicarbonate can be substituted for baking powder provided sufficient acid reagent is also added to the recipe. Many forms of baking powder contain sodium bicarbonate combined with one or more acidic phosphates or cream of tartar.
Neutralization of acids and bases
Many laboratories keep a bottle of sodium bicarbonate powder within easy reach, because sodium bicarbonate is amphoteric, reacting with acids and bases. Furthermore, as it is relatively innocuous in most situations, there is no harm in using excess sodium bicarbonate. Lastly, sodium bicarbonate powder may be used to smother a small fire.
A wide variety of applications follows from its neutralization properties, including ameliorating the effects of white phosphorus in incendiary bullets from spreading inside an afflicted soldier's wounds. Sodium bicarbonate can be added as a simple solution for raising the pH balance of water that has a high level of chlorine, such as in swimming pools and aquariums.
Medical uses
Sodium bicarbonate is used as an antacid to treat acid indigestion and heartburn
An aqueous solution is administered intravenously for cases of acidosis, or when there are insufficient sodium or bicarbonate ions in the blood. This compound has also been used for patients who have had a ureterosigmoidostomy.. It is used as well for treatment of hyperkalemia and cardiorespiratory arrest.
Adverse reactions to emergency administration include congestive heart failure, with edema secondary to sodium overload, and the metabolic complication of hyperosmolarity, metabolic alkalosis, and hypervolemic hypernatremia.
Sodium bicarbonate is also a key material used in hemodialysis, one of the two types of kidney dialysis.
Sodium bicarbonate may also be used as an anti-fungal for dandruff caused by fungus,, as alternative to commercial deodorants and anti-perspirants, and an alternative to shampoo.
Since Sodium bicarbonate can cause alkalosis, it is sometimes used in Aspirin overdoses. The Aspirin requires an acidic environment for proper absorption; the basic environment diminishes aspirin absorption in the case of an overdose
For soda loading
Soda loading is a practice that has been seen primarily in sports, where some coaches and athletes believe that drinking baking soda mixed with water will enhance performance and endurance. In reality, the opposite occurs, and can leave athletes unable to perform.
This practice is also extremely dangerous due to the risk of an overdose of the primary agent sodium bicarbonate, which can be life threatening. Symptoms include constipation, convulsions, diarrhea, feeling of being full, frequent urination, irritability, muscle spasms, muscle weakness and vomiting. If you suspect a baking soda overdose do not make the person to vomit the contents of the stomach unless directed to by a medical professional or poison control.
As a cleaning agent
A paste from baking soda can be very effective when used in cleaning and scrubbing
For cleaning aluminium objects, sodium bicarbonate is to be 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.
It has been used for many years informally as a tooth whitening agent.
Is more effective than vinegar, salt, or hot water alone in removing pesticides from vegetables
Miscellaneous
Sodium bicarbonate is used in BC Dry Chemical fire extinguishers as an alternative to the more corrosive ammonium phosphate in ABC extinguishers. The alkali nature of sodium bicarbonate makes it the only dry chemical agent, besides Purple-K, that was allowed for use on commercial deep fat fryers. The agent has a mild saponification effect on the grease, which forms a smothering soapy foam. Dry Chemicals have since fallen out of favor for kitchen fires as they have no cooling effect compared to the extremely effective wet chemical agents specifically designed for such hazards. However, it can still be used effectively on small grease fires or electrical kitchen fires per manufactures instructions.
It is used in a process for cleaning paint called sodablasting.
It can be administered to pools, spas and garden ponds to raise pH levels.
Because it can be used to absorb odors, it is a tried-and-true method of used booksellers. The baking soda will absorb the musty smell, leaving the books less odorous.
It is commonly added to cocaine as a means of "cutting" the cocaine. It is one of the key ingredients used in the synthesis of crack-cocaine (freebase).
It can be used to neutralize toxic nerve agents like Sarin and Tauben.
See also
Further reading
- Bishop, D., J. Edge, C. Davis, and C. Goodman. "Induced Metabolic Alkalosis Affects Muscle Metabolism and Muscle Metabolism and Repeated-Sprint Ability". Medicine and Science in Sports Exercise, Vol. 36, No. 5, pp. 807-813, 2004.
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