Soda ash

Sodium carbonate

Names
IUPAC name Sodium carbonate
Other names Soda ash, Washing soda, Soda crystals
Identifiers
CAS Number	497-19-8 (anhydrous) Y 5968-11-6 (monohydrate) N 6132-02-1 (decahydrate) N
3D model (Jmol)	Interactive image
ChEBI	CHEBI:29377 Y
ChEMBL	ChEMBL186314 Y
ChemSpider	9916 Y
ECHA InfoCard	100.007.127
EC Number	207-838-8
E number	E500 (acidity regulators, ...)
PubChem	10340
RTECS number	VZ4050000
UNII	45P3261C7T Y
InChI InChI=1S/CH2O3.2Na/c2-1(3)4;;/h(H2,2,3,4);;/q;2*+1/p-2 Y Key: CDBYLPFSWZWCQE-UHFFFAOYSA-L Y InChI=1/NaHCO3.2Na/c2-1(3)4;;/h(H2,2,3,4);;/q;2*+1/p-2 Key: CDBYLPFSWZWCQE-NUQVWONBAP
SMILES [Na+].[Na+].[O-]C([O-])=O
Properties
Chemical formula	Na2CO3
Molar mass	105.9888 g/mol (anhydrous) 286.1416 g/mol (decahydrate)
Appearance	White solid, hygroscopic
Odor	Odorless
Density	2.54 g/cm3 (25 °C, anhydrous) 1.92 g/cm3 (856 °C) 2.25 g/cm3 (monohydrate) 1.51 g/cm3 (heptahydrate) 1.46 g/cm3 (decahydrate)
Melting point	851 °C (1,564 °F; 1,124 K) decomposes (anhydrous) 100 °C (212 °F; 373 K) decomposes (monohydrate) 33.5 °C (92.3 °F; 306.6 K) decomposes (heptahydrate) 34 °C (93 °F; 307 K) (decahydrate)
Solubility in water	Decahydrate: 7 g/100 mL (0 °C) 16.4 g/100 mL (15 °C) 34.07 g/100 mL (27.8 °C) Heptahydrate: 48.69 g/100 mL (34.8 °C) Monohydrate: 50.31 g/100 mL (29.9 °C) 48.1 g/100 mL (41.9 °C) 45.62 g/100 mL (60 °C) 43.6 g/100 mL (100 °C)
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 (15.5 °C)
Solubility in ethanediol	3.46 g/100 g (20 °C)
Solubility in dimethylformamide	0.5 g/kg
Basicity (pKb)	3.67
Magnetic susceptibility (χ)	−4.1·10−5 cm3/mol
Refractive index (nD)	1.485 (anhydrous) 1.420 (monohydrate) 1.405 (decahydrate)
Viscosity	3.4 cP (887 °C)
Structure
Crystal structure	Monoclinic (γ-form, β-form, δ-form, anhydrous) Orthorhombic (monohydrate, heptahydrate)
Space group	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)
Point group	2/m (γ-form, β-form, δ-form, anhydrous) mm2 (monohydrate) 2/m 2/m 2/m (heptahydrate)
Lattice constant	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°
Coordination geometry	Octahedral (Na+, anhydrous)
Thermochemistry
Specific heat capacity (C)	112.3 J/mol·K
Std molar entropy (So298)	135 J/mol·K
Std enthalpy of formation (ΔfHo298)	−1130.7 kJ/mol
Gibbs free energy (ΔfG˚)	−1044.4 kJ/mol
Hazards
Safety data sheet	MSDS
GHS pictograms
GHS signal word	Warning
GHS hazard statements	H319
GHS precautionary statements	P305+351+338
EU classification (DSD)	Xi
R-phrases	R36
S-phrases	(S2), S22, S26
NFPA 704	0 2 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	4090 mg/kg (rat, oral)
Related compounds
Other anions	Sodium bicarbonate
Other cations	Lithium carbonate Potassium carbonate Rubidium carbonate Caesium carbonate
Related compounds	Sodium sesquicarbonate Sodium percarbonate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Sodium carbonate (also known as washing soda, soda ash and soda crystals, and in the monohydrate form as crystal carbonate), Na₂CO₃, is the water-soluble sodium salt of carbonic acid.

It most commonly occurs as a crystalline decahydrate, which readily effloresces to form a white powder, the monohydrate. Pure sodium carbonate is a white, odorless powder that is hygroscopic (absorbs moisture from the air). It has a strongly alkaline taste, and forms a moderately basic solution in water. Sodium carbonate is well known domestically for its everyday use as a water softener. Historically it was extracted from the ashes of plants growing in sodium-rich soils, such as vegetation from the Middle East, kelp from Scotland and seaweed from Spain. Because the ashes of these sodium-rich plants were noticeably different from ashes of timber (used to create potash), they became known as "soda ash". It is synthetically produced in large quantities from salt (sodium chloride) and limestone by a method known as the Solvay process.

The manufacture of glass is one of the most important uses of sodium carbonate. Sodium carbonate acts 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 produced insoluble. This type of glass is known as soda lime glass: "soda" for the sodium carbonate and "lime" for the calcium carbonate. Soda lime glass has been the most common form of glass for centuries.

Sodium carbonate is also used as a relatively strong base in various settings. 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 acts as an alkali because when dissolved in water, it dissociates into the weak acid: carbonic acid and the strong alkali: sodium hydroxide. This gives sodium carbonate in solution the ability to attack metals such as aluminium with the release of hydrogen gas.