Everything about Baking Soda totally explained
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Sodium bicarbonate or
sodium hydrogen carbonate is the
chemical compound with the formula NaHCO
3. Sodium bicarbonate is a white solid that's
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. 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
NaHCO
3 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).
NaHCO
3 may be obtained by the reaction of
carbon dioxide with an aqueous solution of
sodium hydroxide. The initial reaction produces
sodium carbonate:
» CO
2 + 2NaOH → Na
2CO
3 + H
2O
Further addition of
carbon dioxide produces sodium bicarbonate, which at sufficiently high concentration will precipitate out of solution:
» Na
2CO
3 + CO
2 + H
2O → 2NaHCO
3
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:
» Na
2CO
3 + CO
2 + H
2O → 2 NaHCO
3
Chemistry
Sodium bicarbonate is an
amphoteric compound. It has a pK
a of 6.3 in water which causes aqueous solutions to be mildly
alkaline:
» HCO
3- + H
2O → H
2CO
3 +
OH-
Sodium bicarbonate can be used as a wash to remove any acidic impurities from a "crude" liquid, producing a more pure sample. Reaction of sodium bicarbonate and an
acid to give a salt and carbonic acid, which readily decoposes to carbon dioxide and water:
» NaHCO
3 + HCl → NaCl + H
2CO
3
H
2CO
3 → H
2O+ CO
2 (
gas)
Reaction of sodium bicarbonate and acetic acid:
» NaHCO
3 +
CH3COOH →
CH3COONa + H
2O + CO
2 (gas)
Sodium bicarbonate reacts with
bases:
» NaHCO
3 +
NaOH → Na
2CO
3 + H
2O
Thermal decomposition
Above 60 °C, it gradually decomposes into
sodium carbonate,
water and
carbon dioxide. The conversion is fast at 200 °C:
» 2NaHCO
3 →
Na2CO3 + H
2O + CO
2
Most bicarbonates undergo this
dehydration reaction. Further heating converts the carbonate into the oxide (at around 1000°C):
» Na
2CO
3 →
Na2O + CO
2
These conversions are relevant to the use of NaHCO
3 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., hence 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.
For 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. (See
#Chemistry) Furthermore, as it's relatively innocuous in most situations there's no harm in using excess sodium bicarbonate. Lastly, sodium bicarbonate powder may be used to smother a small fire.
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. 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.
Miscellaneous uses
Baking soda has many other miscellaneous uses:
Medical uses
- It is used as an antacid to treat acid indigestion and heartburn
- 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.
- Has also been used as an oral medicine for patients with ureterosigmoidostomy.
As a cleaning agent
A paste from baking soda can be very effective when used in cleaning and scrubbing.
For cleaning of aluminium objects it's 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(External Link
).
Other uses
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 agent, besides Purple-K, allowed for use on commercial deep fat fryers. The agent forms a crust over the surface similar to the effects of a wet chemical.
It is used in a process for cleaning paint called sodablasting.
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.Further Information
Get more info on 'Baking Soda'.
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