Uses
The manufacture of
glass is one of the most important uses of sodium carbonate. When combined with
silica and
calcium carbonate and heated to high temperatures, then cooled rapidly, glass is produced. This type of glass is known as soda lime glass.
Sodium carbonate is also used as a relatively strong
base in various settings. For example, sodium carbonate is used as a pH regulator to maintain stable alkaline conditions necessary for the action of the majority of photographic
developing agents.
It is a common additive in municipal pools used to neutralize the acidic effects of
chlorine and raise pH.
In cooking, it is sometimes used in place of sodium hydroxide for
lyeing, especially with
German pretzels and lye rolls. These dishes are treated with a solution of an alkaline substance in order to change the pH of the surface of the food and thus improve browning.
In
taxidermy, sodium carbonate added to boiling water will remove flesh from the skull or bones of trophies to create the "European skull mount" or for educational display in biological and historical studies.
In chemistry, it is often used as an
electrolyte. This is because electrolytes are usually salt-based, and sodium carbonate acts as a very good conductor in the process of electrolysis. In addition, unlike chloride ions, which form chlorine gas, carbonate ions are not corrosive to the anodes. It is also used as a primary standard for acid-base
titrations because it is solid and air-stable, making it easy to weigh accurately.
Domestic use
In domestic use, it is used as a water softener during laundry. It competes with the magnesium and calcium ions in hard water and prevents them from bonding with the detergent being used. Without using washing soda, additional detergent is needed to soak up the magnesium and calcium ions. Called
washing soda,
soda crystals, or
sal soda in the detergent section of stores, it effectively removes oil, grease, and alcohol stains. Sodium carbonate is also used as a
descaling agent in boilers such as those found in coffee pots,
espresso machines, etc.
In
dyeing with fiber-reactive dyes, sodium carbonate (often under a name such as soda ash fixative or soda ash activator) is used to ensure proper chemical bonding of the dye with cellulose (plant) fibers, typically before dyeing (for tie dyes), mixed with the dye (for dye painting), or after dyeing (for immersion dyeing).
Other applications
Sodium carbonate is a food additive (E500) used as an acidity regulator, anti-caking agent, raising agent, and stabilizer. It is one of the components of
kansui, a solution of alkaline salts used to give
ramen noodles their characteristic flavor and texture. It is also used in the production of
snus (Swedish-style
snuff) to stabilize the pH of the final product. In Sweden,
snus is regulated as a food product because it is put into the mouth, requires pasteurization, and contains only ingredients that are approved as food additives.
Sodium carbonate is also used in the production of
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.
In China, it is used to replace lye-water in the crust of traditional Cantonese
moon cakes, and in many other Chinese steamed buns and noodles.
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 used to create the photo process known as reticulation.
Sodium carbonate, in a solution with common salt, may be used for cleaning silver. In a non-reactive container (glass, plastic or ceramic) aluminium foil and the silver object are immersed in the hot salt solution. The elevated pH dissolves the aluminium oxide layer on the foil and enables an electrolytic cell to be established . Hydrogen ions produced by this reaction reduce the sulphide ions on the silver restoring silver metal. The sulphide can be released as small amounts of hydrogen sulphide. Rinsing and gently polishing the silver restores a highly polished condition.
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