Sodium Bisulfite: Soda Solution Saturated with Sulphur Dioxide (Thorpe 1913)

Sodium bisulfite, NaHSO3, is a white powder smelling of sulphur dioxide, used as a reducing agent, as an antichlor and to make sodium hydrosulphite. Thorpe's Dictionary of Applied Chemistry (1913) makes it by saturating a solution of sodium carbonate with sulphur dioxide (Na2CO3 + 2SO2 + H2O = 2NaHSO3 + CO2) and throwing it out of the solution with alcohol. The amounts are our arithmetic from that equation; the water, the alcohol and the glassware are ours. Source: Thorpe, Dictionary of Applied Chemistry vol. V (1913), SODIUM, p. 19. Picture: that page.