Ammonium acid formate magnesium sulphate

Formamide. Commercial formamide may contain excess of formic acid. It is purified by passing ammonia gas into the mixture until a slight alkaline reaction is obtained. The ammonium formate thus formed is precipitated by the addition of acetone the filtrate, after drying over anhydrous magnesium sulphate, is distilled under reduced pressure. Pure formamide has b.p. IO571I mm. 

Formamide is an excellent solvent for many polar organic compounds and for a selection of inorganic salts. It is very hygroscopic and readily hydrolysed by acids or bases. The commercial product frequently contains formic acid, water and ammonium formate. Purification may be effected by passing ammonia gas into the solvent until a slight alkaline reaction is obtained addition of dry acetone then precipitates the ammonium formate. The filtered solution is dried over magnesium sulphate and fractionally distilled under reduced pressure distillation at atmospheric pressure causes decomposition. Pure formamide has b.p. 105 °C/11 mmHg. 

---