Editing Sodium carbonate (section)

==Applications==
Some common applications of sodium carbonate include:
* As a cleansing agent for domestic purposes like washing clothes. Sodium carbonate is a component of many dry soap powders. It has [[detergent]] properties through the process of [[saponification]], which converts fats and grease to water-soluble [[Salt (chemistry)|salt]]s (specifically, soaps).<ref name=Ullmann/>
* It is used for lowering the [[hardness of water]]<ref name="Cornell" /> (see {{section link|#Water softening}}).
* It is used in the manufacture of [[glass]],<ref name="Himmel">{{Cite book |last1=Himmelblau |first1=David M. |title=Basic principles and calculations in chemical engineering |last2=Riggs |first2=James B. |date=2022 |publisher=Pearson |isbn=978-0-13-732717-1 |edition=Ninth |series=International series in the physical and chemical engineering sciences |location=Boston}}</ref> [[soap]],<ref name="Himmel" /> and [[paper]] {{xref|(see {{slink||Glass manufacture}})}}.
* It is used in the manufacture of sodium compounds like [[borax]] (sodium borate).{{np}}{{pb}}

===Glass manufacture===
Sodium carbonate serves as a [[Flux (metallurgy)|flux]] for [[silica]] (SiO<sub>2</sub>, melting point 1,713&nbsp;°C), lowering the melting point of the mixture to something achievable without special materials. This "soda glass" is mildly water-soluble, so some [[calcium carbonate]] is added to the melt mixture to make the glass insoluble. Bottle and window glass ("[[soda–lime glass]]" with transition temperature ~570&nbsp;°C) is made by melting such mixtures of sodium carbonate, calcium carbonate, and silica sand ([[silicon dioxide]] (SiO<sub>2</sub>)). When these materials are heated, the carbonates release carbon dioxide. In this way, sodium carbonate is a source of sodium oxide. Soda–lime glass has been the most common form of glass for centuries. It is also a key input for tableware glass manufacturing.<ref name=Ullmann/>

===Water softening===
{{See also|Hard water|Water softening}}
Hard water usually contains calcium or magnesium ions. Sodium carbonate is used for removing these ions and replacing them with sodium ions.<ref name="Cornell">{{cite web |url=https://www.ccmr.cornell.edu/wp-content/uploads/sites/2/2015/11/Water-Hardness-Reading.pdf |title=Water Hardness Reading |website=Cornell Center for Materials Research}}</ref>

Sodium carbonate is a water-soluble source of carbonate. The calcium and magnesium ions form insoluble solid precipitates upon treatment with [[carbonate]] ions:
{{block indent|{{chem2|Ca(2+)  +  CO3(2-) -> CaCO3 (s)}}}}
The water is softened because it no longer contains dissolved calcium ions and magnesium ions.<ref name="Cornell" />

===Food additive and cooking===
Sodium carbonate has several uses in cuisine, largely because it is a stronger base than baking soda ([[sodium bicarbonate]]) but weaker than [[lye]] (which may refer to [[sodium hydroxide]] or, less commonly, [[potassium hydroxide]]). Alkalinity affects [[gluten]] production in kneaded doughs, and also improves browning by reducing the temperature at which the [[Maillard reaction]] occurs. To take advantage of the former effect, sodium carbonate is therefore one of the components of {{nihongo3||かん水|kansui}}, a solution of alkaline salts used to give [[Japanese cuisine|Japanese]] [[ramen]] noodles their characteristic flavour and chewy texture; a similar solution is used in [[Chinese cuisine]] to make [[lamian]], for similar reasons. [[Cantonese cuisine|Cantonese]] bakers similarly use sodium carbonate as a substitute for lye-water to give [[moon cake]]s their characteristic texture and improve browning. In [[German cuisine]] (and Central European cuisine more broadly), breads such as [[pretzel]]s and [[lye roll]]s traditionally treated with lye to improve browning can be treated instead with sodium carbonate; sodium carbonate does not produce quite as strong a browning as lye, but is much safer and easier to work with.<ref name="McGee">{{cite news |last1=McGee |first1=Harold |author-link=Harold McGee |title=For Old-Fashioned Flavor, Bake the Baking Soda |url=https://www.nytimes.com/2010/09/15/dining/15curious.html |access-date=25 April 2019 |work=[[The New York Times]] |date=24 September 2010}}</ref>

Sodium carbonate is used in the production of [[sherbet (powder)|sherbet]] powder. The cooling and fizzing sensation results from the endothermic reaction between sodium carbonate and a weak acid, commonly [[citric acid]], releasing carbon dioxide gas, which occurs when the sherbet is moistened by saliva.

Sodium carbonate also finds use in the [[food industry]] as a [[food additive]] ([[E number|European Food Safety Authority number]] E500) as an acidity regulator, [[anticaking agent]], [[leavening agent|raising agent]], and stabilizer. It is also used in the production of {{lang|no|[[snus]]}} to stabilize the pH of the final product.

While it is less likely to cause chemical burns than lye, care must still be taken when working with sodium carbonate in the kitchen, as it is corrosive to aluminum cookware, utensils, and foil.{{tone inline|date=November 2024}}<ref>{{cite web |title=Sodium Carbonate |url=https://www.corrosionpedia.com/definition/2782/sodium-carbonate |website=corrosionpedia |publisher=Janalta Interactive |access-date=9 November 2020}}</ref>{{unreliable source|date=November 2024}}

===Other applications===
Sodium carbonate is also used as a relatively strong [[Base (chemistry)|base]] in various fields. As a common alkali, it is preferred in many chemical processes because it is cheaper than [[sodium hydroxide]] and far safer to handle. Its mildness especially recommends its use in domestic applications.

For example, it is used as a [[pH]] regulator to maintain stable alkaline conditions necessary for the action of the majority of photographic [[Developer (photography)|film developing]] agents. It is also a common additive in [[swimming pool]]s and [[aquarium]] water to maintain a desired pH and carbonate hardness (KH). In [[dyeing]] with fiber-reactive dyes, sodium carbonate (often under a name such as soda ash fixative or soda ash activator) is used as [[mordant]] to ensure proper chemical bonding of the dye with cellulose (plant) fiber. It is also used in the [[froth flotation process]] to maintain a favourable [[pH]] as a float conditioner besides [[CaO]] and other mildly basic compounds.

===Precursor to other compounds===
Sodium {{em|bicarbonate}} (NaHCO<sub>3</sub>) or baking soda, also a component in fire extinguishers, is often generated from sodium carbonate. Although NaHCO<sub>3</sub> is itself an intermediate product of the Solvay process, the heating needed to remove the ammonia that contaminates it decomposes some NaHCO<sub>3</sub>, making it more economical to react finished Na<sub>2</sub>CO<sub>3</sub> with CO<sub>2</sub>:
{{block indent|Na<sub>2</sub>CO<sub>3</sub> + CO<sub>2</sub> + H<sub>2</sub>O → 2NaHCO<sub>3</sub>}}

In a related reaction, sodium carbonate is used to make [[sodium bisulfite]] (NaHSO<sub>3</sub>), which is used for the "sulfite" method of separating [[lignin]] from cellulose. This reaction is exploited for removing [[sulfur dioxide]] from flue gases in power stations:
{{block indent|Na<sub>2</sub>CO<sub>3</sub> + SO<sub>2</sub> + H<sub>2</sub>O → NaHCO<sub>3</sub> + NaHSO<sub>3</sub>}}
This application has become more common, especially where stations have to meet stringent emission controls.

Sodium carbonate is used by the cotton industry to neutralize the sulfuric acid needed for acid delinting of fuzzy cottonseed.

It is also used to form carbonates of other metals by ion exchange, often with the other metals' sulphates.

===Miscellaneous===
Sodium carbonate is used by the brick industry as a wetting agent to reduce the amount of water needed to extrude the clay. In casting, it is referred to as "bonding agent" and is used to allow wet [[alginate]] to adhere to gelled alginate. Sodium carbonate is used in toothpastes, where it acts as a foaming agent and an abrasive, and to temporarily increase mouth pH.

Sodium carbonate is also used in the processing and tanning of animal hides.<ref>{{cite web|title=Home Tanning Hides and Furs|url= https://shareok.org/bitstream/handle/11244/331379/oksa_ANSI-3998_2007-06.pdf?sequence=1&isAllowed=y|access-date=16 April 2024}}</ref>