Sodium formate

Description

Sodium formate, HCOONa, is the sodium salt of formic acid, HCOOH. It usually appears as a white deliquescent powder.

Chemical properties

white crystals

Physical properties

White crystals; slightly hygroscopic; faint odor of formic acid; density 1.92 g/cm³; melts at 253°C; decomposes on further heating, first forming sodium oxalate and hydrogen and then sodium carbonate; very soluble in water; the aqueous solution neutral, pH about 7; soluble in glycerol; slightly soluble in alcohol; insoluble in ether.

Chemical properties

Sodium formate is usually appears as a white deliquescent powder. 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.

The Uses of Sodium formate

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, and as a food additive ( E237 ) .

The Uses of Sodium formate

Precipitant for noble metals.

The Uses of Sodium formate

In dyeing and printing fabrics; also In animal chemistry as a precipitant for the "noble" metals. Solubilizes trivalent metal ions in solution by forming complex ions. Buffering action adjusts the pH of strong mineral acids to higher values.

Definition

ChEBI: An organic sodium salt which is the monosodium salt of formic acid.

Preparation

Sodium formate can be prepared in the laboratory by neutralizing formic acid with sodium carbonate. It can also be obtained by reacting chloroform with an alcoholic solution of sodium hydroxide.
CHCl₃ + 4NaOH → HCOONa + 3NaCl + 2H₂O
or by reacting sodium hydroxide with chloral hydrate.
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.
For commercial use, sodium formate is produced by absorbing carbon monoxide under pressure in solid sodium hydroxide at 160 °C.
CO + NaOH → HCOONa
Sodium formate may also be created via the haloform reaction between ethanol and sodium hypochlorite in the presence of a base.

Preparation

Sodium formate is produced by absorbing carbon monoxide under pressure in solid sodium hydroxide at 130°C and 6-8 bar pressure:CO + NaOH → HCO2Na

Crystal Structure

Sodium formate crystallizes in a monoclinic crystal system with the lattice parameters a = 6,19 ?, b = 6,72 ?, c = 6,49 ? and β = 121,7°.

General Description

Sodium formate is the colorless sodium salt of formic acid. It can be prepared by reacting formic acid with sodium hydroxide or carbonate. Its crystal structure has been investigated. Its crystals exhibit monoclinic-holohedral symmetry.

Flammability and Explosibility

Not classified

Safety Profile

Moderately toxic by ingestion, intravenous, and subcutaneous routes. Combustible when exposed to heat or flame. When heated to decomposition it emits toxic fumes of NazO. See also FORMIC ACID.

Purification Methods

A saturated aqueous solution at 90o (0.8mL water/g) is filtered and allowed to cool slowly. (The final temperature should be above 30o to prevent formation of the hydrate.) After two such crystallissations, the crystals are dried in an oven at 130o, then under high vacuum. [Westrum et al. J Phys Chem 64 1553 1960, Roecker & Meyer J Am Chem Soc 108 4066 1986.] The salt has also been recrystallised twice from 1mM DTPA (diethylenetriaminepentaacetic acid, which was recrystallised 4x from MilliQ water and dried in a vacuum), then twice from water [Bielski & Thomas J Am Chem Soc 109 7761 1987]. [Beilstein 2 IV 3.]