Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, water-soluble salts. All forms have a strongly alkaline taste and give moderately alkaline solutions in water. Historically it was extracted from the ashes of plants growing in sodium-rich soils. Because the ashes of these sodium-rich plants were noticeably different from ashes of wood (once used to produce potash), sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process.
Soda ash, washing soda, soda crystals
3D model (JSmol)
|E number||E500(i) (acidity regulators, ...)|
|Molar mass||105.9888 g/mol (anhydrous)|
286.1416 g/mol (decahydrate)
|Appearance||White solid, hygroscopic|
|Melting point|| 851 °C (1,564 °F; 1,124 K) (Anhydrous)|
100 °C (212 °F; 373 K)
33.5 °C (92.3 °F; 306.6 K)
34 °C (93 °F; 307 K)
|Anhydrous, g/100 mL:|
|Solubility||Soluble in aq. alkalis, glycerol|
Slightly soluble in aq. alcohol
Insoluble in CS2, acetone, alkyl acetates, alcohol, benzonitrile, liquid ammonia
|Solubility in glycerine||98.3 g/100 g (155 °C)|
|Solubility in ethanediol||3.46 g/100 g (20 °C)|
|Solubility in dimethylformamide||0.5 g/kg|
Refractive index (nD)
|Viscosity||3.4 cP (887 °C)|
|Monoclinic (γ-form, β-form, δ-form, anhydrous)|
Orthorhombic (monohydrate, heptahydrate)
|C2/m, No. 12 (γ-form, anhydrous, 170 K)|
C2/m, No. 12 (β-form, anhydrous, 628 K)
P21/n, No. 14 (δ-form, anhydrous, 110 K)
Pca21, No. 29 (monohydrate)
Pbca, No. 61 (heptahydrate)
|2/m (γ-form, β-form, δ-form, anhydrous)|
2/m 2/m 2/m (heptahydrate)
a = 8.920(7) Å, b = 5.245(5) Å, c = 6.050(5) Å (γ-form, anhydrous, 295 K)
α = 90°, β = 101.35(8)°, γ = 90°
|Octahedral (Na+, anhydrous)|
Heat capacity (C)
Std enthalpy of
Gibbs free energy (ΔfG˚)
|Safety data sheet||MSDS|
|GHS signal word||Warning|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|4090 mg/kg (rat, oral)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Sodium carbonate is obtained as three hydrates and as the anhydrous salt:
The decahydrate is formed from water solutions crystallizing in the temperature range -2.1 to +32.0 C, the heptahydrate in the narrow range 32.0 to 35.4 C and above this temperature the monohydrate forms. In dry air the decahydrate and heptahydrate lose water to give the monohydrate. Other hydrates have been reported, e.g. with 2.5 units of water per sodium carbonate unit ("pentahemihydrate").
In terms of its largest applications, sodium carbonate is used in the manufacture of glass, paper, rayon, soaps, and detergents.
Sodium carbonate serves as a flux for silica, 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) 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.
Sodium carbonate is an inexpensive and water-soluble source of carbonate ions.
Sodium carbonate is a food additive (E500) used as an acidity regulator, anticaking agent, raising agent, and stabilizer. It is one of the components of kansui (かん水), a solution of alkaline salts used to give ramen noodles their characteristic flavor and texture. It is used in the production of snus to stabilize the pH of the final product. 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. 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. 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 to change the pH of the surface of the food and improve browning.
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 NaOH 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 film developing agents. It is also a common additive in swimming pools 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 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). 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.
Sodium bicarbonate (NaHCO3) or baking soda, also a component in fire extinguishers, is often generated from sodium carbonate. Although NaHCO3 is itself an intermediate product of the Solvay process, the heating needed to remove the ammonia that contaminates it decomposes some NaHCO3, making it more economic to react finished Na2CO3 with CO2:
In a related reaction, sodium carbonate is used to make sodium bisulfite (NaHSO3), 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:
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.
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 soluble in water, and can occur naturally in arid regions, especially in mineral deposits (evaporites) formed when seasonal lakes evaporate. Deposits of the mineral natron have been mined from dry lake bottoms in Egypt since ancient times, when natron was used in the preparation of mummies and in the early manufacture of glass.
The anhydrous mineral form of sodium carbonate is quite rare and called natrite. Sodium carbonate also erupts from Ol Doinyo Lengai, Tanzania's unique volcano, and it is presumed to have erupted from other volcanoes in the past, but due to these minerals' instability at the earth's surface, are likely to be eroded. All three mineralogical forms of sodium carbonate, as well as trona, trisodium hydrogendicarbonate dihydrate, are also known from ultra-alkaline pegmatitic rocks, that occur for example in the Kola Peninsula in Russia.
Extraterrestrially, known sodium carbonate is rare. Deposits have been identified as the source of bright spots on Ceres, interior material that has been brought to the surface. While there are carbonates on Mars, and these are expected to include sodium carbonate, deposits have yet to be confirmed, this absence is explained by some as being due to a global dominance of low pH in previously aqueous Martian soil.
Trona, trisodium hydrogendicarbonate dihydrate (Na3HCO3CO3·2H2O), is mined in several areas of the US and provides nearly all the domestic consumption of sodium carbonate. Large natural deposits found in 1938, such as the one near Green River, Wyoming, have made mining more economical than industrial production in North America. There are important reserves of trona in Turkey; two million tons of soda ash have been extracted from the reserves near Ankara. It is also mined from some alkaline lakes such as Lake Magadi in Kenya by dredging. Hot saline springs continuously replenish salt in the lake so that, provided the rate of dredging is no greater than the replenishment rate, the source is fully sustainable.
Several "halophyte" (salt-tolerant) plant species and seaweed species can be processed to yield an impure form of sodium carbonate, and these sources predominated in Europe and elsewhere until the early 19th century. The land plants (typically glassworts or saltworts) or the seaweed (typically Fucus species) were harvested, dried, and burned. The ashes were then "lixiviated" (washed with water) to form an alkali solution. This solution was boiled dry to create the final product, which was termed "soda ash"; this very old name refers to the archetypal plant source for soda ash, which was the small annual shrub Salsola soda ("barilla plant").
The sodium carbonate concentration in soda ash varied very widely, from 2–3 percent for the seaweed-derived form ("kelp"), to 30 percent for the best barilla produced from saltwort plants in Spain. Plant and seaweed sources for soda ash, and also for the related alkali "potash", became increasingly inadequate by the end of the 18th century, and the search for commercially viable routes to synthesizing soda ash from salt and other chemicals intensified.
In 1792, the French chemist Nicolas Leblanc patented a process for producing sodium carbonate from salt, sulfuric acid, limestone, and coal. In the first step, sodium chloride is treated with sulfuric acid in the Mannheim process. This reaction produces sodium sulfate (salt cake) and hydrogen chloride:
The salt cake and crushed limestone (calcium carbonate) was reduced by heating with coal. This conversion entails two parts. First is the carbothermic reaction whereby the coal, a source of carbon, reduces the sulfate to sulfide:
The second stage is the reaction to produce sodium carbonate and calcium sulfide:
This mixture is called black ash. The soda ash is extracted from the black ash with water. Evaporation of this extract yields solid sodium carbonate. This extraction process was termed lixiviation.
The hydrochloric acid produced by the Leblanc process was a major source of air pollution, and the calcium sulfide byproduct also presented waste disposal issues. However, it remained the major production method for sodium carbonate until the late 1880s.
The sodium bicarbonate was then converted to sodium carbonate by heating it, releasing water and carbon dioxide:
The Solvay process recycles its ammonia. It consumes only brine and limestone, and calcium chloride is its only waste product. The process is substantially more economical than the Leblanc process, which generates two waste products, calcium sulfide and hydrogen chloride. The Solvay process quickly came to dominate sodium carbonate production worldwide. By 1900, 90% of sodium carbonate was produced by the Solvay process, and the last Leblanc process plant closed in the early 1920s.
The second step of the Solvay process, heating sodium bicarbonate, is used on a small scale by home cooks and in restaurants to make sodium carbonate for culinary purposes (including pretzels and alkali noodles), as sodium bicarbonate is commonly available as baking soda and the temperatures required (250 °F (121 °C) to 300 °F (149 °C)) to convert baking soda to sodium carbonate can be achieved in conventional kitchen ovens.
This process was developed by Chinese chemist Hou Debang in the 1930s. The earlier steam reforming byproduct carbon dioxide was pumped through a saturated solution of sodium chloride and ammonia to produce sodium bicarbonate by these reactions:
The sodium bicarbonate was collected as a precipitate due to its low solubility and then heated up to approximately 80 °C (176 °F) or 95 °C (203 °F) to yield pure sodium carbonate similar to last step of the Solvay process. More sodium chloride is added to the remaining solution of ammonium and sodium chlorides; also, more ammonia is pumped at 30-40 °C to this solution. The solution temperature is then lowered to below 10 °C. Solubility of ammonium chloride is higher than that of sodium chloride at 30 °C and lower at 10 °C. Due to this temperature-dependent solubility difference and the common-ion effect, ammonium chloride is precipitated in a sodium chloride solution.
The Chinese name of Hou's process, lianhe zhijian fa (联合制碱法), means "coupled manufacturing alkali method": Hou's process is coupled to the Haber process and offers better atom economy by eliminating the production of calcium chloride, since ammonia no longer needs to be regenerated. The byproduct ammonium chloride can be sold as a fertilizer.
Alkali salts or basic salts are salts that are the product of the neutralization of a strong base and a weak acid.
Rather than being neutral (as some other salts), alkali salts are bases as their name suggests. What makes these compounds basic is that the conjugate base from the weak acid hydrolyzes to form a basic solution. In sodium carbonate, for example, the carbonate from the carbonic acid hydrolyzes to form a basic solution. The chloride from the hydrochloric acid in sodium chloride does not hydrolyze, though, so sodium chloride is not basic.
The difference between a basic salt and an alkali is that an alkali is the soluble hydroxide compound of an alkali metal or an alkaline earth metal. A basic salt is any salt that hydrolyzes to form a basic solution.
Another definition of a basic salt would be a salt that contains amounts of both hydroxide and other anions. White lead is an example. It is basic lead carbonate, or lead carbonate hydroxide.
These materials are known for their high levels of dissolution in polar solvents.
These salts are insoluble and are obtained through precipitation reactions.Alkali soil
Alkali, or Alkaline, soils are clay soils with high pH (> 8.5), a poor soil structure and a low infiltration capacity. Often they have a hard calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their unfavorable physico-chemical properties mainly to the dominating presence of sodium carbonate, which causes the soil to swell and difficult to clarify/settle. They derive their name from the alkali metal group of elements, to which sodium belongs, and which can induce basicity. Sometimes these soils are also referred to as alkaline sodic soils.they also have local names like reh,kallal,rakar.
Alkaline soils are basic, but not all basic soils are alkaline.Barilla
Barilla refers to several species of salt-tolerant (halophyte) plants that, until the 19th Century, were the primary source of soda ash and hence of sodium carbonate. The word "barilla" was also used directly to refer to the soda ash obtained from plant sources. The word is an anglicization of the Spanish word barrilla for saltwort plants (a particular category of halophytes).
A very early reference indicating the value placed upon soda ash in Catalonia has been given by Glick, who notes that "In 1189 the monastery of Poblet granted to the glassblower Guillem the right to gather glasswort in return for tithe and two hundred pounds of sheet glass paid annually (The site of these glassworks, at Narola, was excavated in 1935.)." By the 18th Century, Spain's barilla industry was exporting large quantities of soda ash of exceptional purity; the product was refined from the ashes of barilla plants that were specifically cultivated for this purpose. Presumably the word "barilla" entered English and other languages as a consequence of this export trade. The main Spanish barilla species included (i) Salsola soda (the common English term barilla plant for Salsola soda reflects this usage), (ii) Salsola kali, and (iii) Halogeton sativus (formerly Salsola sativa). Fairly recently, Pérez has concluded that the most prominent species was likely Halogeton sativus; earlier authors have tended to favor Salsola soda.
The word "barilla" was also used directly to refer to soda ash from any plant source, including not only the saltworts grown in Spain, but also glassworts, mangroves, and seaweed. These types of plant-derived soda ash are impure alkali substances that contain widely varying amounts of sodium carbonate (Na2CO3), some additional potassium carbonate (also an alkali), and a predominance of non-alkali impurities. The sodium carbonate, which is water-soluble, is "lixiviated" (extracted with water) from the ashes of the burned, dried plants. The resulting solution is boiled dry to obtain the finished barilla. A very similar process is used to obtain potash (mainly potassium carbonate) from the ashes of hardwood trees. The best Spanish barilla—prepared by master barrilleros—contained about 30% Na2CO3. In 1877 Kingzett described the importance of the barilla trade to Spain as follows: "So highly was the product valued, and the importance of the trade regarded, that by the laws of Spain the exportation of the seed was an offence punishable by death."Some authors indicate that "barilla" was a specific plant used for soda ash production; this usage is erroneous, but presumably corresponds to the common usage of "barilla plant" exclusively for Salsola soda. Perhaps this common usage itself reflects an old error in assuming that a single plant species was used by the Spaniards for their industry. In still earlier times, the sources of soda ash and the methods of processing it were secrets that were zealously guarded.Caffenol
Caffenol is a photographic alternative process whereby phenols, sodium carbonate and optionally Vitamin C are used in aqueous solution as a film and print photographic developer.Other basic (as opposed to acidic) chemicals can be used in place of sodium carbonate, however sodium carbonate is the most common.There are many formulas for caffenol. All are based on preparations which contain caffeic acid (i.e. coffee or tea) and a pH modifier, most often sodium carbonate. The chemistry of caffenol developers is based on the action of the reducing agent caffeic acid (which is chemically unrelated to caffeine).Carbaldrate
Carbaldrate (dihydroxyaluminum sodium carbonate) is an antacid.Caustic embrittlement
Caustic embrittlement is the phenomenon in which the material of a boiler becomes brittle due to the accumulation of caustic substances.Deville process
The Deville process was the first industrial process used to produce alumina from bauxite.
The Frenchman Henri Sainte-Claire Deville invented the process in 1859. It is sometimes called the Deville-Pechiney process.
It is based on the extraction of alumina with sodium carbonate.
The first stage is the calcination of the bauxite at 1200 °C with sodium carbonate and coke. The alumina is converted in sodium aluminate. Iron oxide remains unchanged and silica forms a polysilicate.
In the second stage sodium hydroxide solution is added, which dissolves the sodium aluminate, leaving the impurities as a solid residue. The amount of sodium hydroxide solution needed depends upon the amount of silica present in the raw material. The solution is filtered off; carbon dioxide is bubbled through the solution, causing aluminium hydroxide to precipitate, leaving a solution of sodium carbonate. The latter can be recovered and reused in the first stage.
The aluminium hydroxide is calcined to produce alumina.
The process was used in France at Salindres until 1923 and in Germany and Great Britain until the outbreak of the Second World War.It has now been replaced by the Bayer process.Glasswort
The glassworts are various succulent, annual halophytes plants, that is, plants that thrive in saline environments, such as seacoasts and salt marshes. The original English glasswort plants belong to the genus Salicornia, but today the glassworts include halophyte plants from several genera, some of which are native to continents unknown to the medieval English, and growing in ecosystems, such as mangrove swamps, never envisioned when the term glasswort was coined.
The common name "glasswort" came into use in the 16th century to describe plants growing in England whose ashes could be used for making soda-based (as opposed to potash-based) glass.Grand Rapids Eastern Railroad
The Grand Rapids Eastern Railroad (reporting mark GR) is a railroad in western Michigan, United States. The line runs east–west through Grand Rapids, Michigan to Lowell. Its 47 miles (76 km) of trackage ends at the Saint Mary's Siding, where it meets the Coopersville and Marne Railway. It interchanges with CSX Transportation and the Grand Elk Railroad at Grand Rapids. It was established in 1993 and purchased by RailAmerica in 2000. The railroad was later acquired by Genesee & Wyoming Inc. as part of its acquisition of RailAmerica in late 2012.
Most of the railroad's traffic comes from grain, lumber, and sodium carbonate. The GR hauled around 1,250 carloads in 2008.Leblanc process
The Leblanc process was an early industrial process for the production of soda ash (sodium carbonate) used throughout the 19th century, named after its inventor, Nicolas Leblanc. It involved two stages: production of sodium sulfate from sodium chloride, followed by reaction of the sodium sulfate with coal and calcium carbonate to produce sodium carbonate. The process gradually became obsolete after the development of the Solvay process.List of companies of Chad
Chad is a landlocked country in Central Africa. Chad's currency is the CFA franc. In the 1960s, the Mining industry of Chad produced sodium carbonate, or natron. There have also been reports of gold-bearing quartz in the Biltine Prefecture. However, years of civil war have scared away foreign investors; those who left Chad between 1979 and 1982 have only recently begun to regain confidence in the country's future. In 2000 major direct foreign investment in the oil sector began, boosting the country's economic prospects.Natron
Natron is a naturally occurring mixture of sodium carbonate decahydrate (Na2CO3·10H2O, a kind of soda ash) and around 17% sodium bicarbonate (also called baking soda, NaHCO3) along with small quantities of sodium chloride and sodium sulfate. Natron is white to colourless when pure, varying to gray or yellow with impurities. Natron deposits are sometimes found in saline lake beds which arose in arid environments. Throughout history natron has had many practical applications that continue today in the wide range of modern uses of its constituent mineral components.
In modern mineralogy the term natron has come to mean only the sodium carbonate decahydrate (hydrated soda ash) that makes up most of the historical salt.Residual sodium carbonate index
The residual sodium carbonate (RSC) index of irrigation water or soil water is used to indicate the alkalinity hazard for soil. The RSC index is used to find the suitability of the water for irrigation in clay soils which have a high cation exchange capacity. When dissolved sodium in comparison with dissolved calcium and magnesium is high in water, clay soil swells or undergoes dispersion which drastically reduces its infiltration capacity.In the dispersed soil structure, the plant roots are unable to spread deeper into the soil due to lack of moisture. However, high RSC index water does not enhance the osmotic pressure to impede the off take of water by the plant roots unlike high salinity water. Clay soils irrigation with high RSC index water leads to fallow alkali soils formation.Sodium Carbonate Company
Sodium Carbonate Company (Persian: شركت كربنات سديم – Sherḵat-e Karbonāt Sodīm) is a village and company town in Lasgerd Rural District, Sorkheh District, in the Central District of Sorkheh County, Iran. At the 2006 census, its population was 37, in 14 families.Sodium bicarbonate
Sodium bicarbonate (IUPAC name: sodium hydrogen carbonate), commonly known as baking soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation (Na+) and a bicarbonate anion (HCO3−). Sodium bicarbonate is a white solid that is crystalline, but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate). The natural mineral form is nahcolite. It is a component of the mineral natron and is found dissolved in many mineral springs.Sodium percarbonate
Sodium percarbonate is a chemical substance with formula Na2H3CO6. It is an adduct of sodium carbonate ("soda ash" or "washing soda") and hydrogen peroxide (that is, a perhydrate) whose formula is more properly written as 2 Na2CO3 · 3 H2O2. It is a colorless, crystalline, hygroscopic and water-soluble solid. It is sometimes abbreviated as SPC. It contains 32.5% by weight of hydrogen peroxide.
The product is used in some eco-friendly bleaches and other cleaning products, and as a laboratory source of anhydrous hydrogen peroxide.Sodium sesquicarbonate
Sodium sesquicarbonate (systematic name: trisodium hydrogendicarbonate) Na3H(CO3)2 is a double salt of sodium bicarbonate and sodium carbonate (NaHCO3 · Na2CO3), and has a needle-like crystal structure. However, the term is also applied to an equimolar mixture of those two salts, with whatever water of hydration the sodium carbonate includes, supplied as a powder.
The dihydrate, Na3H(CO3)2 · 2H2O, occurs in nature as the evaporite mineral trona.Due to concerns about the toxicity of borax which was withdrawn as a cleaning and laundry product, sodium sesquicarbonate is sold in the European Union (EU) as "Borax substitute". It is also known as one of the E number food additives E500.Solvay process
The Solvay process or ammonia-soda process is the major industrial process for the production of sodium carbonate (soda ash, Na2CO3). The ammonia-soda process was developed into its modern form by Ernest Solvay during the 1860s. The ingredients for this are readily available and inexpensive: salt brine (from inland sources or from the sea) and limestone (from quarries). The worldwide production of soda ash in 2005 has been estimated at 42 million metric tons, which is more than six kilograms (13 lb) per year for each person on Earth. Solvay-based chemical plants now produce roughly three-quarters of this supply, with the remaining being mined from natural deposits. This method superseded the Leblanc process.Trona
Trona (trisodium hydrogendicarbonate dihydrate, also sodium sesquicarbonate dihydrate, Na2CO3•NaHCO3•2H2O) is a non-marine evaporite mineral. It is mined as the primary source of sodium carbonate in the United States, where it has replaced the Solvay process used in most of the rest of the world for sodium carbonate production.