NEW MATERIAL:2-Sulfonylamino-5-alkoxybenzenesulfonic acids expressed by formula I (R1 is alkyl or cycloalkyl : R2 is alkyl, cycloalkyl or aryl; M is H or alkali metal).

EXAMPLE: 2-Methanesulfonylamino-5-methoxybenzenesulfonic acid.

USE: Useful as an intermediate for photographic additives and compounds having surface activating action.

PREPARATION: A sulfonylamino-1-alkoxybenzene expressed by formula II is preferably sulfonated with chlorosulfonic acid or 60-95% sulfuric acid to afford the compounds expressed by formula I. The sulfonating reaction is carried out at preferably 50-200°C, especially at -20 to 12O°C by using a solvent (e.g. acetic acid).