Misplaced Pages

This is an old revision of this page, as edited by 72.155.89.175 (talk) at 03:32, 21 February 2007. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

You must add a |reason= parameter to this Cleanup template – replace it with {{Cleanup|January 2007|reason=<Fill reason here>}}, or remove the Cleanup template.

Sodium bicarbonate
General
Systematic name	Sodium hydrogen carbonate
Other names	Sodium bicarbonate bicarbonate of soda
Molecular formula	NaHCO3
Molecular Weight	84.007 g/mol
Exact Mass	83.982
Appearance	White crystalline solid.
CAS number	144-55-8
Properties
Density and phase	2.159 g/cm³, solid.
Solubility in water	7.8g/100g water @ 18C (64F)
Other solvents e.g. ethanol	"slightly"
Melting point	50°C (323.15 K)
Boiling point	Decomposes.
Basicity (pKb)	6.3
Structure
Molecular shape	?
Coordination geometry	?
Crystal structure	?
Hazards
MSDS	External MSDS
Main hazards	Irritant, especially to the respiratory system
NFPA 704	NFPA 704 safety square 1
Flash point	Non-flammable.
R/S statement	R: ? S: ?
RTECS number	VZ0950000
Supplementary data page
Structure and properties	n = 1.500
Thermodynamic data	Phase behaviour Solid
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	Sodium carbonate, carbonic acid
Other cations	?
Related compounds	Sodium hydrogen sulphate sodium hydrogen phosphate
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references

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 hydrogen carbonate, sodium bicarb, baking soda, bread soda, cooking soda, bicarb soda, saleratus or bicarbonate of soda. It is soluble in water. This white solid 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. It is also produced artificially.

Production

NaHCO₃ is mainly prepared by the Solvay process, which entails the reaction of sodium chloride, ammonia, and carbon dioxide in water. It is produced on the scale of 100,000 ton/year (year: 2001).

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 solution:

Na₂CO₃ + CO₂ + H₂O → 2 NaHCO₃

Acid-base reactions

NaHCO₃ is a salt which consists of the ions Na and the bicarbonate anion, HCO₃. In aqueous solution, these ions are separated. Furthermore the bicarbonate anion forms some hydroxide, which results in its solutions being mildly alkaline:

HCO₃ → CO₂ + OH

NaHCO₃ is obtained by the reaction of carbon dioxide with sodium hydroxide:

CO₂ + NaOH → NaHCO₃

It reacts further with NaOH to produce the related salt, sodium carbonate:

NaHCO₃ + NaOH → Na₂CO₃ + H₂O

These reactions are reversible. Treatment of sodium bicarbonate with an acid, releases carbon dioxide and water:

NaHCO₃ + HCl → NaCl + H₂O + CO₂ (gas)

NaHCO₃ + CH₃C(O)OH → NaO₂CCH₃ + 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.

History

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.

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 cream of tartar, lemon juice, yogurt, etc. Some forms of baking powder contain sodium bicarbonate combined with cream of tartar.

• A small amount can be added to a beef stew to make tough meat tenderize faster.
• Sodium bicarbonate is used to give pretzels their dark brown color.
• Was formerly used as a source of carbon dioxide for soda water.
• Can be used when preparing tomato sauce to neutralize the tomato's acidity.
• It is added to beans in water to prevent flatulence produced when eating them.
• It is effective in extinguishing grease fires which may occur when deep frying.

For neutralization of acids

The reaction of acids with sodium bicarbonate is a common method for neutralizing acid spills. The advantage to this method is that one can use excess sodium carbonate, which is relatively innocuous. The neutralization process is signaled by the release of gaseous CO₂. A wide variety of applications follow from its neutralization properties including ameliorating the effects of white phosphorus in incendiary bullets, from spreading inside a soldier's afflicted wounds. Military Application

• It is commonly used to increase the pH and 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.
• It neutralizes battery acid.

Miscellaneous and domestic uses

This section's factual accuracy is disputed. Relevant discussion may be found on the talk page. Please help to ensure that disputed statements are reliably sourced. (Learn how and when to remove this message)

Baking soda has many uses.

As a deodorizer

• An absorbent for moisture and odors; 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.
• Can be used to clean vacuum flasks, especially after they've developed an odor from not being used for a long time whilst being stored with the cap on.
• As a substitute for talcum powder to prevent foot odor.
• To clean a microwave oven from lingering odors.
• Rubbed into one's hands to remove odors from food preparation.

As pest control

• It kills fleas and drives away ants. If it is applied to a pet's fur, it must be washed/rinsed off to prevent skin problems.
• Can be used to kill crab grass. Must be used repeatedly to control but is effective. Dampen area then sprinkle lightly, too much may harm desired grass temporarily.
• The bottom part of a door frame can be lined with sodium bicarbonate to keep out ants.

Medical uses

• If made into a paste salve with vinegar, it relieves burning from bug stings (particularly bee stings), poison ivy, nettles, and sunburn.
• It is used as an antacid to treat acid indigestion and heartburn.
• Mixed with water in a 10% solution can soften earwax for removal.
• In paramedicine, sodium bicarbonate 8.4% 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.

Cosmetic uses

• It is marketed as a whitener in some toothpaste brands.
• Add to hair if it's dirty and there's no time to wash it. Dry with warm air.

As a cleaning agent

• A paste from baking soda can be very effective when used in cleaning and scrubbing.
• A solution in warm water will remove the tarnish from silver when the silver is in contact with a piece of aluminum foil.
• With water, it cleans the impurities on contact lenses. Rinse completely before wearing contacts to avoid stinging of the salt in baking soda.
• Cleans brushes and combs to prevent residues.
• Mix into a paste to clean the surface of an iron.
• Use to clean juice, wine, and coffee stains.
• Washing a car with it can remove dead bug bodies without damaging the paint.
• Pour 1 cup of baking soda down a drain and follow with 1/2 gallon of White Vinegar will degrease the drain.

Other uses

• Baking soda and boiling water unclogs drains.
• It is used as a fabric softener in laundry.
• It is used to test garden soil for acidity. If it bubbles, the soil is too acidic.
• Sodium bicarbonate has been used as a performance enhancer for sprinters, by countering build up of lactate through induced metabolic alkalosis.
• If mixed with super glue, it makes a suitable filling for cracks in walls.
• Combined with cocaine to make crack cocaine.
• Sprinkle on wet pages of books and then put them out to dry under the sun.
• It is used in the Aquarium hobby to raise the pH of the water and in the production of CO₂ in yeast mixes.
• 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(not including Purple-K) agent allowed for use on commercial deep fat fryers, the agent forms a crust over the surface similar to the effects of Wet Chemical.

Safety

Sodium bicarbonate is considered to be relatively safe, however consumption of large amounts should be avoided. See MSDS.

References

1. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.

2. 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.

See also

• Baking powder
• Natron
• List of minerals
• Sodium carbonate
• Carbonic acid
• Soda

External links

• Material Safety Data Sheet
• Free to read Baking Soda Book
• Baking Soda at MadeHow.com
• How Baking Soda Works (howstuffworks.com)

Template:ChemicalSources

• Sodium compounds
• Bicarbonates
• Fire suppression agents
• Household chemicals
• Leavening agents