The phase behaviour of ten aqueous mixtures of an alkanediol saturated with sodium carbonate was studied: between 40 and 90 degrees C the solubility of sodium carbonate was measured in mixtures with different alkane-diol to water ratios. Six systems featured phase separation: polyethylene-glycol 200, polyethylene-glycol 400, tri-ethylene-glycol, 1,2-butanediol, 1,3-butanediol and 1,4-butanediol. Four antisolvents were fully miscible: ethylene glycol, di-ethylene-glycol, glycerol, and 1,2-propanediol. Solubility measurements showed that di-ethylene-glycol is the best antisolvent: sodium carbonate recoveries of 99% are achievable.