Sodium formate

Sodium formate,HCOONa, is the sodium salt offormic acid,HCOOH. It usually appears as a whitedeliquescentpowder.

Sodium formate

Ball-and-stick model of the formate anion
Names
Systematic IUPAC name Sodium methanoate
Other names formic acid, sodium salt
Identifiers
CAS Number	141-53-7Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:62965
ChEMBL	ChEMBL183491N
ChemSpider	8517Y
ECHA InfoCard	100.004.990
EC Number	205-488-0
E number	E237(preservatives)
PubChemCID	2723810
UNII	387AD98770Y
CompTox Dashboard(EPA)	DTXSID2027090
InChI InChI=1S/CH2O2.Na/c2-1-3;/h1H,(H,2,3);/q;+1/p-1Y Key: HLBBKKJFGFRGMU-UHFFFAOYSA-MY InChI=1/CH2O2.Na/c2-1-3;/h1H,(H,2,3);/q;+1/p-1 Key: HLBBKKJFGFRGMU-REWHXWOFAN
SMILES [Na+].[O-]C=O
Properties
Chemical formula	HCOONa
Molar mass	68.007 g/mol
Appearance	white granules deliquescent
Density	1.92 g/cm3(20 °C)
Melting point	253 °C (487 °F; 526 K)
Boiling point	decomposes
Solubility in water	43.82 g/100 mL (0 °C) 97.2 g/100 mL (20 °C) 160 g/100 mL (100 °C)
Solubility	insoluble inether soluble inglycerol,alcohol,formic acid
Thermochemistry
Heat capacity(C)	82.7 J/mol K
Std molar entropy(S⦵298)	103.8 J/mol K
Std enthalpy of formation(ΔfH⦵298)	-666.5 kJ/mol
Gibbs free energy(ΔfG⦵)	-599.9 kJ/mol
Hazards
NFPA 704(fire diamond)	1 0 0
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa). Nverify(what isYN?) Infobox references

Preparation

For commercial use, sodium formate is produced by absorbingcarbon monoxideunder pressure in solidsodium hydroxideat 130 °C and 6-8 bar pressure:

CO + NaOH → HCO₂Na

Because of the low-cost and large-scale availability offormic acidby carbonylation of methanol and hydrolysis of the resulting methyl formate, sodium formate is usually prepared byneutralizingformic acid withsodium hydroxide.Sodium formate is also unavoidably formed as a by-product in the final step of thepentaerythritolsynthesis and in the crossedCannizzaro reactionofformaldehydewith the aldol reaction product trimethylol acetaldehyde [3-hydroxy-2,2-bis(hydroxymethyl)propanal].

In the laboratory, sodium formate can be prepared by neutralizingformic acidwithsodium carbonate.It can also be obtained by reactingchloroformwith an alcoholic solution ofsodium hydroxide.

CHCl₃+ 4 NaOH → HCOONa + 3 NaCl + 2 H₂O

or by reactingsodium hydroxidewithchloral hydrate.

C₂HCl₃(OH)₂+ NaOH → CHCl₃+ HCOONa + H₂O

The latter method is, in general, preferred to the former because the low aqueous solubility ofCHCl₃makes it easier to separate out from the sodium formate solution, byfractional crystallization,than the solubleNaClwould be.

Properties

Physical properties

Some sodium formate dihydrate crystals

Sodium formate crystallizes in amonoclinic crystal systemwith thelattice parametersa = 6,19 Å, b = 6,72 Å, c = 6,49 Å and β = 121,7°.

Chemical properties

On heating, sodium formate decomposes to formsodium oxalateand hydrogen.The resulting sodium oxalate can be converted by further heating tosodium carbonateupon release of carbon monoxide:

${\ce {2HCOONa->[\Delta ]{(COO)2Na2}+H2\!\uparrow }}$

${\ce {(COO)2Na2->[{} \atop >\ {\ce {290^{o}C}}]{Na2CO3}+CO\!\uparrow }}$

As asaltof a weak acid (formic acid) and astrong base(sodium hydroxide) sodium formate reacts in aqueous solutions basic:

${\ce {HCOO^- + H2O <<=> HCOOH + OH^-}}$

A solution of formic acid and sodium formate can thus be used as abuffersolution.

Sodium formate is slightly water-hazardous and inhibits some species of bacteria but is degraded by others.

Uses

Sodium formate is used in several fabric dyeing and printing processes. It is also used as abuffering agentfor strong mineral acids to increase theirpH,as a food additive (E237), and as ade-icingagent.

Instructural biology,sodium formate can be used as acryoprotectantfor X-ray diffraction experiments on protein crystals,which are typically conducted at a temperature of 100 K to reduce the effects ofradiation damage.

Sodium formate plays a role in thesynthesisofformic acid,it is converted by sulfuric acid via the following reaction equation:

$\mathrm {2\ HCOONa+H_{2}SO_{4}\longrightarrow 2\ HCOOH+Na_{2}SO_{4}}$

Sodium formate is converted with sulfuric acid to formic acid andsodium sulfate.

Theurticating hairofstinging nettlescontain sodium formate as well as formic acid.

Solid sodium formate is used as a non-corrosive agent atairportsfor de-icing of runways in mix with corrosion inhibitors and other additives, which rapidly penetrate solid snow and ice layers, detach them from the asphalt or concrete and melt the ice rapidly. Sodium formate was also used as a road deicer in the city ofOttawafrom 1987 to 1988.

The high freezing point depression e.g. in comparison to the still frequently usedurea(which is effective but problematic due toeutrophication) effectively prevents the re-icing, even at temperatures below −15 °C. The thawing effect of the solid sodium formate can even be increased by moistening with aqueouspotassium formateorpotassium acetatesolutions. The degradability of sodium formate is particularly advantageous with a chemical oxygen demand (COD) of 211 mgO₂/g compared with the de-icing agentssodium acetate(740 mg O₂/g) and urea with (> 2,000 mg O₂/g).

Saturated sodium formate solutions (as well as mixtures of other alkali metal formates such as potassium and cesium formate) are used as important drilling and stabilizing aids in gas andoil explorationbecause of their relatively high density. By mi xing the corresponding saturated alkali metal formate solutions any densities between 1,0 and 2,3 g/cm³can be set. The saturated solutions arebiocidalandlong-term stableagainst microbial degradation. Diluted, on the other hand, they are fast and completely biodegradable. As alkali metal formates as drilling aids make it unnecessary to add solid fillers to increase the density (such asbarytes) and the formate solutions can be recovered andrecycledat the drilling site, formates represent an important advance in exploration technology.

See also

• Sodium acetate