|Systematic IUPAC name
formic acid, sodium salt, sodium hydrocarbon dioxide
3D model (Jmol)
|E number||E237 (preservatives)|
|Molar mass||68.007 g/mol|
|Density||1.92 g/cm3 (20 °C)|
|Melting point||253 °C (487 °F; 526 K)|
|43.82 g/100 mL (0 °C)
97.2 g/100 mL (20 °C)
160 g/100 mL (100 °C)
|Solubility||insoluble in ether
soluble in glycerol, alcohol, formic acid
|Acidity (pKa)||7.0-8.5 (0.1M)|
|82.7 J/mol K|
|103.8 J/mol K|
Std enthalpy of
Gibbs free energy (ΔfG˚)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
- CO + NaOH → HCO2Na
Because of the low-cost and large-scale availability of methanoic acid by carbonylation of methanol and hydrolysis of the resulting methyl formate, sodium formate is usually prepared by neutralizing methanoic acid with sodium hydroxide. Sodium formate is also unavoidably formed as a by-product in the final step of the pentaerythritol synthesis and in the crossed Cannizzaro reaction of methanal with the aldol reaction product trimethylol acetaldehyde [3-hydroxy-2,2-bis(hydroxymethyl)propanal].
- CHCl3 + 4 NaOH → HCOONa + 3 NaCl + 2 H2O
- C2HCl3(OH)2 + NaOH → CHCl3 + HCOONa + H2O
The latter method is, in general, preferred to the former because the low aqueous solubility of CHCl3 makes it easier to separate out from the sodium formate solution, by fractional crystallization, than the soluble NaCl would be.
On heating, sodium formate decomposes to form sodium oxalate and hydrogen. The resulting sodium oxalate can be converted by further heating to sodium carbonate upon release of carbon monoxide:
A solution of formic acid and sodium formate can thus be used as a buffer 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 a buffering agent for strong mineral acids to increase their pH, as a food additive (E237), and as a de-icing agent.
In structural biology, sodium formate can be used as a cryoprotectant for X-ray diffraction experiments on protein crystals, which are typically conducted at a temperature of 100 °K to reduce the effects of radiation damage.
- Sodium formate is converted with sulfuric acid to methanoic acid and sodium sulfate.
Solid sodium formate is used as a non-corrosive agent at airports 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.
The high freezing point depression e.g. in comparison to the still frequently used urea (which is effective but problematic due to eutrophication) 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 aqueous potassium formate or potassium acetate solutions. The degradability of sodium formate is particularly advantageous with a chemical oxygen demand (COD) of 211 mg O2/g compared with the de-icing agents sodium 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 and oil 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 are biocidal and long-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 as barytes) and the formate solutions can be recovered and recycled at the drilling site, formates represent an important advance in exploration technology.
- Arnold Willmes, Taschenbuch Chemische Substanzen, Harri Deutsch, Frankfurt (M.), 2007.
- H.-J. Arpe, Industrielle Organische Chemie, 6., vollst. überarb. Aufl., Wiley-VCH Verlag, 2007, ISBN 978-3-527-31540-6
- W. H. Zachariasen: "The Crystal Structure of Sodium Formate, NaHCO2" in J. Am. Chem. Soc., 1940, 62(5), S. 1011–1013. doi:10.1021/ja01862a007
- T. Meisel, Z. Halmos, K. Seybold, E. Pungor: "The thermal decomposition of alkali metal formates" in Journal of Thermal Analysis and Calorimetry 1975, 7(1). S. 73-80. doi:10.1007/BF01911627
- T. Yoshimori, Y. Asano, Y. Toriumi, T. Shiota: "Investigation on the drying and decomposition of sodium oxalate" in Talanta 1978, 25(10) S. 603-605. doi:10.1016/0039-9140(78)80158-1
- Bujacz, G.; Wrzesniewska, B.; Bujacz, A. (2010), "Cryoprotection properties of salts of organic acids: a case study for a tetragonal crystal of HEW lysozyme", Acta Crystallographica Section D: Biological Crystallography, 66 (7), pp. 789–796, doi:10.1107/S0907444910015416
- Deicer Anti-icing Snow melting Thawing Chemicals Manufacturers
- William Benton and Jim Turner, Cabot Specialty Fluids: Cesium formate fluid succeeds in North Sea HPHT field trials (PDF; 88 kB); In: Drilling Contractor, Mai/Juni 2000.