Formate or methanoate is the ion HCOO− (formic acid minus one hydrogen ion). It is the simplest carboxylate anion. A formate (compound) is a salt or ester of formic acid.
Ammonium Formate
Ammonium formate, NH4HCO2, is the ammonium salt of formic acid. It is a colorless, hygroscopic, crystalline solid. Pure ammonium formate decomposes into formamide and water when heated, and this is its primary use in industry. Formic acid can also be obtained by reacting ammonium formate with a dilute acid, and since ammonium formate is also produced from formic acid, it can serve as a way of storing formic acid.
Sodium Formate
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 generally 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.
Commercially sodium formate is produced by absorbing carbon monoxide under pressure in solid sodium hydroxide at 160 °C
CO + NaOH → HCOONa
