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