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| Names | |||
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| Systematic IUPAC name Sodium methanoate | |||
Other names
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| Identifiers | |||
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3D model (JSmol) | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider |
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| ECHA InfoCard | 100.004.990 | ||
| EC Number |
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| E number | E237(preservatives) | ||
| UNII | |||
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| Properties | |||
| 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 | ||
| 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 | |||
| 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) | |||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Sodium formate, HCOONa, is the sodium salt offormic acid, HCOOH. It usually appears as a whitedeliquescent powder.
For commercial use, sodium formate is produced by absorbingcarbon monoxide under pressure in solidsodium hydroxide at 130 °C and 6-8 bar pressure:[1]
Because of the low-cost and large-scale availability offormic acid by carbonylation of methanol and hydrolysis of the resulting methyl formate, sodium formate is usually prepared byneutralizing formic acid withsodium hydroxide. Sodium formate is also unavoidably formed as a by-product in the final step of thepentaerythritol synthesis and in the crossedCannizzaro reaction offormaldehyde with the aldol reaction product trimethylol acetaldehyde [3-hydroxy-2,2-bis(hydroxymethyl)propanal].[2]
In the laboratory, sodium formate can be prepared by neutralizingformic acid withsodium carbonate. It can also be obtained by reactingchloroform with an alcoholic solution ofsodium hydroxide.
or by reactingsodium hydroxide withchloral hydrate.
The latter method is, in general, preferred to the former because the low aqueous solubility ofCHCl3 makes it easier to separate out from the sodium formate solution, byfractional crystallization, than the solubleNaCl would be.
Sodium formate crystallizes in amonoclinic crystal system with thelattice parameters a = 6,19 Å, b = 6,72 Å, c = 6,49 Å and β = 121,7°.[3]
On heating, sodium formate decomposes to formsodium oxalate and hydrogen.[4] The resulting sodium oxalate can be converted by further heating tosodium carbonate upon release of carbon monoxide:[5][4]
As asalt of a weak acid (formic acid) and astrong base (sodium hydroxide) sodium formate reacts in aqueous solutions basic:
A solution of formic acid and sodium formate can thus be used as abuffer solution.
Sodium formate is slightly water-hazardous and inhibits some species of bacteria but is degraded by others.
Sodium formate is used in several fabric dyeing and printing processes. It is also used as abuffering agent for strong mineral acids to increase theirpH, as a food additive (E237), and as ade-icing agent.
Instructural biology, sodium formate can be used as acryoprotectant for X-ray diffraction experiments on protein crystals,[6] which are typically conducted at a temperature of 100 K to reduce the effects ofradiation damage.
Sodium formate plays a role in thesynthesis offormic acid, it is converted by sulfuric acid via the following reaction equation:
Theurticating hair ofstinging nettles contain sodium formate as well as formic acid.
Solid sodium formate is used as a non-corrosive agent atairports for 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 ofOttawa from 1987 to 1988.[7]
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 formate orpotassium acetate solutions. 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).[8]
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 exploration because of their relatively high density. By mixing the corresponding saturated alkali metal formate solutions any densities between 1,0 and 2,3 g/cm3 can be set. The saturated solutions arebiocidal andlong-term stable against 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 andrecycled at the drilling site, formates represent an important advance in exploration technology.[9]
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