| Sodium bicarbonate | |
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Sodium hydrogen carbonate |
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Other names
Baking soda, bicarbonate of soda, nahcolite, sodium bicarbonate, sodium hydrogencarbonate |
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| Identifiers | |
| CAS number | 144-55-8 |
| PubChem | 516892 |
| ChemSpider | 8609 |
| UNII | 8MDF5V39QO |
| EC number | 205-633-8 |
| DrugBank | DB01390 |
| KEGG | C12603 |
| MeSH | Sodium+bicarbonate |
| ChEBI | CHEBI:32139 |
| ChEMBL | CHEMBL1353 |
| RTECS number | VZ0950000 |
| ATC code | B05,B05XA02 |
| Beilstein Reference | 4153970 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | CHNaO3 |
| Molar mass | 84.01 g mol−1 |
| Exact mass | 83.982338573 g mol−1 |
| Appearance | White crystals |
| Density | 2.20 g cm−3[1] |
| Melting point |
50 °C, 323 K, 122 °F (decomposes) |
| Boiling point |
851 °C, 1124 K, 1564 °F |
| Solubility in water | 9 g/100 mL
69 g/L (0 °C)[2] |
| log P | -0.82 |
| Acidity (pKa) | 10.329[4]
6.351 (carbonic acid)[4] |
| Refractive index (nD) | 1.3344 |
| Pharmacology | |
| Routes of administration |
Intravenous, oral |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | Causes serious eye irritation |
| NFPA 704 |
0
1
0
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| LD50 | 4.22 g kg− |
| Related compounds | |
| Other anions | Sodium carbonate |
| Other cations | Ammonium bicarbonate |
| Related compounds | Sodium bisulfate |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. 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 found in dissolved form in bile, where it serves to neutralize the acidity of the hydrochloric acid produced by the pancreas, and is excreted into the duodenum of the small intestine via the bile duct. 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, and bicarbonate of soda. In colloquial usage, its name is shortened to sodium bicarb, bicarb soda, or simply 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.
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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, 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 to develop baking soda from sodium carbonate and carbon dioxide.[5]
This compound, referred to as saleratus, is mentioned in the famous novel Captains Courageous by Rudyard Kipling as being used extensively in the 1800s in commercial fishing to prevent freshly-caught fish from spoiling.[6]
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. It is produced on the scale of about 100,000 tonnes/year (as of 2001).[7]
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:
Naturally occurring deposits of nahcolite (NaHCO3) are found in the Eocene-age (55.8–33.9 Ma) 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 in-situ leach techniques involving dissolution of the nahcolite by heated water that is pumped through the nahcolite beds and reconstituted through a natural cooling crystallization process.
Sodium bicarbonate is an amphoteric compound. Aqueous solutions are 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 CO2. This reaction is used to test for the presence of carboxylic groups in protein.
Above 70 °C, sodium bicarbonate gradually decomposes into sodium carbonate, water and carbon dioxide. The conversion is fast at 200 °C:[8]
Most bicarbonates undergo this dehydration reaction. Further heating converts the carbonate into the oxide (at ca. 1000 °C):
These conversions are relevant to the use of NaHCO3 as a fire-suppression agent ("BC powder") in some dry powder fire extinguishers.
Sodium bicarbonate, referred to as "baking soda" is primarily used in cooking (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, and other baked and fried foods. 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.[9] Many forms of baking powder contain sodium bicarbonate combined with one or more acidic phosphates (especially good) 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 that contain more nutrients. However, it is still used in Asian cuisine to tenderise meats. Baking soda may react with acids in food, including Vitamin C (L-ascorbic acid). It is also used in breadings such as for fried foods to enhance crispness.
Thermal decomposition causes sodium bicarbonate alone to act as a raising agent by releasing carbon dioxide at baking temperatures. The carbon dioxide production starts at temperatures above 80 °C. The mixture for cakes using this method can be allowed to stand before baking without any premature release of carbon dioxide.
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. Also, sodium bicarbonate powder may be used to smother a small fire, as heating of sodium bicarbonate releases carbon dioxide.[10]
A wide variety of applications follows from its neutralization properties, including reducing the spread of white phosphorus from incendiary bullets inside an afflicted soldier's wounds.[11] Sodium bicarbonate can be added as a simple solution for raising the pH balance of water (increasing total alkalinity) where high levels of chlorine (2–5 ppm) are present as in swimming pools and aquariums.[12]
Sodium bicarbonate is used in an aqueous solution as an antacid taken orally to treat acid indigestion and heartburn.[13] It may also be used in an oral form to treat chronic forms of metabolic acidosis such as chronic renal failure and renal tubular acidosis. Sodium bicarbonate may also be useful in urinary alkalinization for the treatment of aspirin overdose and uric acid renal stones. It is used as the medicinal ingredient in gripe water for infants.[14]
Sodium bicarbonate has been known to be used in first aid, in treating scalding, to prevent blistering and scarring with instructions to cover the scalded area with a liberal layer of sodium bicarbonate and water paste and seek medical assistance. This is due to the endothermic reaction that occurs between sodium bicarbonate and water and sodium bicarbonates mild antiseptic properties[15]
Intravenous sodium bicarbonate is an aqueous solution that is sometimes used for cases of acidosis, or when there are insufficient sodium or bicarbonate ions in the blood.[16] 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 marked (<7.1–7.0) low.[17]
It is used as well for treatment of hyperkalemia. 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.[18] It can also be applied topically as a paste, with three parts baking soda to one part water, to relieve insect bites.[19]
Adverse reactions to the administration of sodium bicarbonate can include metabolic alkalosis, edema due to sodium overload, congestive heart failure, hyperosmolar syndrome, hypervolemic hypernatremia, and hypertension due to increased sodium. In patients consuming a high-calcium or dairy-rich diet, calcium supplements, or calcium-containing antacids such as calcium carbonate (e.g., Tums), the use of sodium bicarbonate can cause milk-alkali syndrome, which can result in metastatic calcification, kidney stones, and kidney failure.
Sodium bicarbonate can be used to cover an allergic reaction of poison ivy, oak, or sumac to relieve some of the itching that is associated with it (an alternative to buying hydrocortisone cream).[20]
Sodium bicarbonate can be used as an exfoliant. Its particles are rounded and fine in texture, making it both effective and gentle on the skin. Using baking soda as an exfoliating scrub removes dead skin cells, which can be discolored from hyperpigmentation and scarring.
Sodium bicarbonate is also used as an ingredient in some mouthwashes. It works as a mechanical cleanser on the teeth and gums, neutralizes the production of acid in the mouth and also acts as an antiseptic to help prevent infections.
A paste made from sodium bicarbonate and a 3% hydrogen peroxide solution can be used as an alternative to commercial non-fluoride toothpastes, and sodium bicarbonate in combination with other ingredients can be used to make a dry or wet deodorant. It may also be used as a shampoo.[21]
Small amounts of sodium bicarbonate have been shown to be useful as a supplement for athletes in speed-based events, like middle distance running, lasting from about one to seven minutes.[22][23] But overdose is a serious risk because sodium bicarbonate is slightly toxic[24] and in particular gastrointestinal irritation is of concern.[23] Additionally this practice causes a significant increase in dietary sodium.
A paste from baking soda can be very effective when used in cleaning and scrubbing.[25] 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.[26][27]
Baking soda is commonly added to washing machines as a replacement for softener and also to remove odors from clothes. Sodium bicarbonate is also effective in removing heavy tea and coffee stains from cups when diluted with warm water.
Sodium bicarbonate can be an effective way of controlling fungus growth,[28] and in the United States is registered by the Environmental Protection Agency as a biopesticide.[29]
Sodium bicarbonate is sold as a cattle feed supplement, in particular as a buffering agent for the rumen.
Sodium bicarbonate can be used to extinguish small grease or electrical fires by being thrown over the fire.[10] However, it should not be applied to fires in deep fryers, as it may cause the grease to splatter.[10] 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 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. 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.
Sodium bicarbonate is used in a process for cleaning paint called sodablasting. It can be administered to pools, spas, and garden ponds to raise pH levels.[30] It has weak disinfectant properties,[31][32] and it may be an effective fungicide against some organisms.[33]
Since it acts as a neutralizing agent, it can be used to absorb odors that are caused by strong acids. It is a tried-and-true method of used-book sellers. The baking soda will absorb the musty smell, leaving the books less malodorous.[34]
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