Common applications 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 salts (specifically, soaps).
- It is used for lowering the hardness of water[16] (see § Water softening).
- It is used in the manufacture of glass, soap, and paper (see § Glass manufacture).
- It is used in the manufacture of sodium compounds like borax.
Glass manufacture
Sodium carbonate serves as a flux for silica (SiO2, melting point 1,713 °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 °C) is made by melting such mixtures of sodium carbonate, calcium carbonate, and silica sand (silicon dioxide (SiO2)). 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
Water softening
Hard water usually contains calcium or magnesium ions. Sodium carbonate is used for removing these ions and replacing them with sodium ions.
Food additive and cooking
See also: Water Hardness
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.
Sodium carbonate is 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.
Sodium carbonate also finds use in food industry as a food additive (E500) as an acidity regulator, anticaking agent, raising agent, and stabilizer. It is also used in the production of 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.
Other applications
Sodium carbonate is also used as a relatively strong 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.
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.