Carbonation

Carbonation occurs when carbon dioxide is dissolved in water or an aqueous solution. This process yields the "fizz " to carbonated water and sparkling mineral water, the head to beer, and the cork pop and bubbles to champagne and sparkling wine.

Effervescence

Effervescence is the escape of gas from an aqueous solution. The term is used to describe the foaming or fizzing that results from a release of gas. In the lab, a common example of effervescence is the addition of hydrochloric acid to a block of limestone. If a few pieces of marble or an antacid tablet are put in hydrochloric acid in a test tube fitted with a cork, effervescence of carbon dioxide can be witnessed.

$mbox\{CaCO\}\_\{3\}\; +\; 2mbox\{HCl\}\; longrightarrow\; mbox\{H\}\_\{2\}mbox\{CO\}\_3\; +\; mbox\{CaCl\}\_\{2\}$

Another chemical reaction that produces gas is the reaction of sodium bicarbonate with acid, for example in Alka-Seltzer brand tablets, used to treat stomach indigestion. The essential chemical reaction is:

$mbox\{citric\; acid\}\; +\; mbox\{sodium\; bicarbonate\}\; longrightarrow\; mbox\{water\}\; +\; mbox\{carbon\; dioxide\}\; +\; mbox\{sodium\; citrate\}$

$mbox\{C\}\_6mbox\{H\}\_8mbox\{O\}\_7\; +\; mbox\{3\}mbox\{Na\}mbox\{HC\}mbox\{O\}\_3\; longrightarrow\; mbox\{3\}mbox\{H\}\_2mbox\{O\}\; +\; mbox\{3\}mbox\{CO\}\_2\; +mbox\{Na\}\_3mbox\{C\}\_6mbox\{H\}\_5mbox\{O\}\_7$

The process of carbon dioxide bubbling out of solution is generally represented by the following reaction, where a pressurized dilute solution of carbonic acid in water releases gaseous carbon dioxide at decompression:

$mbox\{H\}\_2mbox\{CO\}\_3\; longrightarrow\; mbox\{H\}\_2mbox\{O\}\; +\; mbox\{CO\}\_2$

In simple terms, it is the result of the chemical reaction occurring in the liquid which produces a gaseous product.

Fizz

"Fizz" is a word used to describe the action or sound of gas bubbles moving through and escaping from a liquid. Fizz also describes the formation of a foam of this gas and liquid at the top of the liquid's container. The word itself is an example of onomatopoeia, derived from the sound the multiple bubbles make together as they "pop" when they escape. A carbonated beverage, such as cola or beer, will form bubbles when the dissolved carbon dioxide is depressurized to form emulsions at the top, and it will make "fizzing" sounds when it is opened or poured into a container. In the United Kingdom, soft drinks are often referred to as 'fizzy drinks'. A cocktail based on carbonated water and an acidic juice is called a Fizz, such as the Gin Fizz.

Measuring carbonation

The quality of carbonated beverages including soft drinks, seltzer and beer is affected by the amount of dissolved CO₂ (the gas that causes carbonation) and the amount of carbonic acid in the drink. Carbon dioxide (CO₂) has an infrared absorption wavelength of 4.27 micrometers and can be measured online using an infrared carbonation sensor. This is an improvement to the traditional inferred measurement method using temperature and pressure for Henry's Law coefficients because this methodology is influenced by changes in density and alcohol content. Infrared measurements are not affected by changes in density or alcohol content because they are actually measuring the CO₂ molecule using the Beer-Lambert law. The amount of carbonation in a beverage is measured in Volumes or grams/liter. This is because introducing CO₂ into a beverage will change its weight. An easy experiment to prove this is to take a seltzer bottle and weigh it. Carefully remove the top slowly so no liquid escapes from the bottle as the gas escapes the weight of the bottle of seltzer will go down. Shaking the bottle closed and then opening it to remove more CO₂ will increase this effect.

Natural and forced carbonation

Carbonation can occur as a result of natural processes: when yeast ferments dissolved sugars sealed in a pressure-tolerant bottle or keg; when underground volcanic carbon dioxide carbonates well water; or when rainwater passes through limestone into a cave and forms a stalactite. Or it can be done artificially by dissolving carbon dioxide under pressure into the liquid. Sometimes natural carbonation is called "conditioning" while the term "carbonation" or "forced carbonation" is reserved for the artificial process.

Uses

In many consumer beverages such as soft drinks (well known examples include Coca-Cola, 7 Up,
Fanta and Pepsi), carbonation is used to give "bite". The fizzy taste can be caused by dilute carbonic acid inducing a slight burning sensation, but is never caused by the presence of bubbles.Fact|date=June 2008 This can be shown by drinking a fizzy drink in a hyperbaric chamber at the same pressure as the beverage. This can give much the same taste as at sea level. In any case, the bubbles will be completely absent during this experience. If you were to taste a flat soda at this pressure, you might experience a much different flavor profile as carbonic acid has a low vapor pressure, and the only "bite" would come from other acids in the soda. However in the case of coca-cola, and pepsi, much of the perceived bite is due to phosphoric acid, an acid not known for fizz or changes in flavor profile due to changes in pressure.

Carbonation is sometimes used for reasons other than consumption for example:1. To reduce the availability of free oxygen in a soda.2. To reduce the ph in a liquid by marginal amountIn the cleaning industry (Chem-Dry and Carbonated Solutions both use carbonated cleaning solutions for carpet cleaning) due to micro environments produced by the carpet cleaning equipment where super critical CO2 becomes an incredibly effective solvent for organics.

Brewing

In homebrewing, overcarbonation can be dangerous; it can result in bottles gushing or even exploding. Adding priming sugar or malt extract at bottling time to beer that has had its fermentable sugar content totally consumed is the safest approach to carbonation. Exceeding recommended levels of priming sugar for a given recipe is dangerous, as is using inappropriate bottles or improper capping methods. Beer may also be force-carbonated using a keg and special bottling equipment so that the carbonation level can be carefully controlled.

Further reading

* — Kinch describes in detail the theory and practice of constructing one's own home carbonation system.

References

* —O'Leary describes in detail the theory and practice of measuring dissolved CO₂ content in soft drinks and beer.

ee also

*Alka Seltzer
*Beer
*Carbonated water
*Champagne
*Charmat process
*Cola
*Dry Soda
*Diet Coke and Mentos eruption, uses carbonated liquid
*Fizzix
*Méthode champenoise
*Nucleation
*Pop rocks carbonated candy
*Sparkling wine
*Soft drink
*Tonic water
*Liftoff

External links

* [http://www.newton.dep.anl.gov/askasci/chem00/chem00459.htm Carbonation and Acidity]
* [http://www.allaboutbeer.com/features/206.gas3.html From Velvety Foam to Rocky Head - Ray Daniels]
* [http://www.job-stiftung.de/index.php?id=31,138,0,0,1,0 Dissolution of Marble in Hydrochloric Acid] Demonstration experiment: Instruction and video