Sodium bicarbonate

Sodium bicarbonate is the chemical compound with the formula NaHCO₃. Because it has long been known and is widely used, the salt has many other names including sodium hydrogencarbonate, sodium bicarb, baking soda, bread soda, cooking soda, bicarb soda or bicarbonate of soda. 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.

It is soluble in water. 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 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.

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Production

Main article: Solvay process

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 (year: 2001).^[1]

Commercial quantities of baking soda are also produced by this 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 → 2 NaHCO₃

Chemistry

Acid-base reactions

NaHCO₃ is a salt which consists of the ions Na⁺ and the bicarbonate anion, HCO₃^-. It has a pK_a of 6.3 in water which causes aqueous solutions to be mildly alkaline:

HCO₃^- + H₂O --> H₂CO₃ + OH^-

Reaction of sodium hydroxide with carbon dioxide

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

Decomposition

Reaction of sodium bicarbonate and an acid:

NaHCO₃ + HCl → NaCl + H₂CO₃

This then decomposes into carbon dioxide and water:

H₂CO_{3 →} H₂O+ CO₂ (gas)

NaHCO₃ + CH₃COOH → CH₃CO₂Na + H₂O + CO₂ (gas)

Thermal decomposition

Above 60 °C, it gradually decomposes into sodium carbonate, water and carbon dioxide. The conversion is fast at 200 °C:

2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

Most bicarbonates undergo this dehydration reaction. Further heating converts the carbonate into the oxide:

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

Main article: leavening agent

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 cream of tartar, lemon juice, yogurt etc., hence sodium bicarbonate can be substituted for baking powder provided sufficient acid reagent is also added to the recipe.^[2]. Many forms of baking powder contain sodium bicarbonate combined with cream of tartar.

• A small amount can be added to meat as a tenderizer, a technique common in Chinese cuisine.
• Was formerly used as a source of carbon dioxide for soda water.
• It can be used when preparing tomato sauce to neutralize the tomato's acidity.
• It is added to water used to soak beans; this is said to prevent flatulence.
• It is effective in extinguishing grease fires which may occur when deep frying.
• In Thailand, soaking insects in baking soda for three to five hours prior to cooking produces a sweeter, more mushroom-like taste in the finished cuisine.
• Freshly cut fruit can be soaked in sodium bicarbonate solution for a short while to prevent yellowing.

For neutralization of acids and bases

The reaction of acids with sodium bicarbonate is a common method for neutralizing acid and base spills. The advantage of sodium bicarbonate is that it is amphoteric, hence reacts with acids and bases. For example, with sulfuric acid:

2 NaHCO₃ + H₂SO₄ → Na₂SO₄ + 2 H₂O + 2 CO₂

With sodium hydroxide:

NaHCO₃ + NaOH → Na₂CO₃ + H₂O

Furthermore, as it is relatively innocuous in most situations there is no harm in using excess sodium bicarbonate.

A wide variety of applications follow from its neutralization properties including ameliorating the effects of white phosphorus in incendiary bullets, from spreading inside an afflicted soldier's wounds.^[3]

• It is commonly used to increase the pH [thereby increasing the total alkalinity] of the water for pools and spas. Sodium bicarbonate can be added as a simple solution for restoring the pH balance of water that has a high level of chlorine.
• It is sometimes used in septic tanks to control pH and bacteria.

Miscellaneous and domestic uses

Baking soda has many uses. [1] Bottle rockets: vinegar and baking soda

As a deodorizer

• An absorbent for moisture and odors e.g; an open box can be left in a refrigerator for this purpose. However, according to one source, baking soda does not actually absorb odors well when used in a refrigerator.
• To help relieve itching due to bacterial infections

Medical uses

• It is used as an antacid to treat acid indigestion and heartburn
• Mixed with water and drunk, it can relieve cystitis.
• Mixed with water in a 10% solution can soften earwax for removal.
• In paramedicine, sodium bicarbonate 7.9% is administered intravenously for cases of acidosis and overdoses of acidic toxic substances, such as tricyclic antidepressants and aspirin.
• Adverse reactions to emergency administration include congestive heart failure, with edema secondary to sodium overload, and the metabolic complication of hyperosmolarity, metabolic acidosis, and hypernatremia.
• Aids in itch relief from poison ivy rashes.
• Added to a bath or made into a paste it can be used to relieve the itching caused by chicken pox.
• For local injections of anesthetics subdermally or subcutaneously, it may be added to lessen the burning sensation of the anesthetic to the patient. For example. 9 milliliters of lidocaine mixed with 1 milliliter of sodium bicarb in a 10 cc syringe will greatly lessen the feeling of burning, pressure and overall pain from the injection.
• Relieves mosquito bites and bee stings (but not wasp stings).
• Has also been used as an oral medicine for patients with ureterosigmoidostomy.
• Is in Alka-seltzer tablets

Cosmetic uses

• It is marketed as a whitener because of its abrasive properties in some toothpaste brands.
• It can also be used as a topical treatment for acne, when mixed with water into a paste.

As a cleaning agent

• A paste from baking soda can be very effective when used in cleaning and scrubbing.
• For cleaning of aluminum objects it is to be discouraged as it attacks the thin protective oxide layer of this otherwise very un-reactive metal.
• A solution in warm water will remove the tarnish from silver when the silver is in contact with a piece of aluminum foil[2].
• Cleans brushes and combs to prevent residues.
• Use to clean juice, wine, and coffee stains.
• Pouring 1 cup of baking soda down a drain and following with 1/2 gallon of vinegar will degrease the drain.
• Baking soda was the primary cleaning agent in the restoration of the statue of liberty.
• A solution of baking soda in warm water will clean corrosion from zinc-carbon and lead acid battery terminals. DO NOT use sodium bicarbonate on alkaline batteries, as they leak caustic potassium hydroxide. Instead, use a 50/50 solution of white vinegar and water to neutralize the KOH leakage from alkaline batteries.

Other uses

• It is used as a fabric softener in laundry.^{[citation needed]}
• Sodium bicarbonate has been used as a performance enhancer for sprinters, by countering build up of lactate through induced metabolic alkalosis.^{[citation needed]}
• Baking soda can be used as a low-cost alternative to raise pH in swimming pools.^[4]
• Sodium bicarbonate is used in BC Dry Chemical fire extinguishers as an alternative to the corrosive ammonium phosphate in ABC extinguishers. The alkali nature of sodium bicarbonate makes it the only dry powder, excluding Purple-K, agent allowed for use on commercial deep fat fryers, the agent forms a crust over the surface similar to the effects of a wet chemical.^{[citation needed]}
• Sodium bicarbonate is often used in the pharmaceutical industry as an additive to cell culture media. It acts as a weak buffer.
• It is used in a process for cleaning paint called sodablasting.
• It is used as a base in the production of crack cocaine.
• It is used as an effective anti dandruff treatment. Allow to soak one minute about three times a week to start then just once a month. Results will vary from case to case.^{[citation needed]}
• It can be used as a carbon sequestration agent, as demonstrated by the Skymine process, to trap Carbon Dioxide greenhouse gas emissions in solid form, as one potential tool against global warming.^[5]

See also

• Natron
• Nahcolite
• List of minerals
• Carbonic acid

References

1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
2. ^ Radiation Cookery Book 45th Edition, Radiation Group Sales Ltd 1954
3. ^ White Phosphorus. GlobalSecurity.org. Retrieved on 2007-09-26.
4. ^ Outdoor Fun: Pool Care. Arm & Hammer Baking Soda (2003). Retrieved on 2007-09-26.
5. ^ Can baking soda cub global warming?. CNet News (2007). Retrieved on 2007-12-30.

Further reading

1. 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.