Sodium hydrosulphite - made from sodium formate

摘要

Prepn. of Na2S2O4 (sodium hydrosulphite) from a sodium formate HCOONa comprises; (A) absorbing SO2 in methanol giving feed soln. (1) (B) adding NaOH and HCOONa to water and heating to dissolve all solids giving feed solution (2); (C) feeding a small quantity of methanol as feed solution (3) to a reactor, heating to 60-90 degrees C, and agitating under pressure; (D) feeding under pressure solns. (1) and (2) to the reactor, agitating and heating to 60-90 degrees C; (E) Expelling the CO2 from the reaction liquid; (F) Cooling the reactor and contents; (G) Filtering off the solid Na2S2O4 from the reaction liquid; and (H) recovering the methyl formate from the reaction liquid and recycling with soln. (3).