PURPOSE: An aqueous dispersant excellent in resistance to polyvalent ions and an ability to disperse finely divided inorganic powder, containing, as an effective component, a water-soluble or water-dispersible polymeric salt of a copolymer consisting mainly of a dicyclopentadiene type monomer and an α,β-unsaturated dicarboxylic acid anhydride and containing a sulfo group and an acid anhydride group.

CONSTITUTION: A water-soluble or water dispersible polymeric salt in which at least part of the sulfo groups and acid anhydride groups of a sulfonated product of an addition copolymer, number-average MW500W20,000, between a dicyclopentadiene type monomer and an α,β-unsaturated dicarboxylic acid anhydride, e.g., maleic anhydride, form salt group. An aqueous dispersant containing the aqueous polymeric salt as an effective component has an excellent ability to disperse finely divided inorganic powders, such as inorganic colloid, and excellent in resistance and stability to polyvalent metal ions. This dispersant can be used as a usual aqueous dispersant, and can also be suitably used in applications where polyvalent metal ions are present at high concentrations, to which conventional dispersants have limited use.