[C:1]([NH:4][C:5]1[CH:10]=[CH:9][C:8]([S:11](Cl)(=[O:13])=[O:12])=[CH:7][CH:6]=1)(=[O:3])[CH3:2].S([O-])([O-])=O.[Na+].[Na+].[OH-].[Na+].S(=O)(=O)(O)O>O>[C:1]([NH:4][C:5]1[CH:6]=[CH:7][C:8]([S:11]([OH:13])=[O:12])=[CH:9][CH:10]=1)(=[O:3])[CH3:2]To 4-acetamidobenzenesulphonyl chloride (400 g, 1.72 moles) was added with stirring a solution of sodium sulphite (431.7 g, 3.42 moles) in water (2 liters). A solution of 50% sodium hydroxide (240 ml) was added dropwise over 35 minutes using a cooling bath to keep the temperature below 30° C. The pH was thus maintained in the range 6.5-7.0. The mixture was stirred at room temperature for 2 hours and acidified by adding conc. sulphuric acid (170 ml) with ice-bath cooling. The precipitated white solid was filtered off, washed with water and dried at 50° C. The yield was 324.2 g (94%). This was used in the next stage without further purification.
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