A stable liquid dispersion in an non-polar organic solvent containing an alkylsulphonylhalopyridine and a dispersing agent which is the reaction product of a hydroxyalkylcarboxylic acid and an amine or salt thereof. The alkylsulphonylhalopyridine may be 2,3,5,6-tetrachloro-4-(methylsulphenyl)pyridine and the hydroxycarboxylic acid may be poly(12-hydroxystearic acid) and the amine may be either dimethylamino propylamine or polyethyleneimine. The solvent may be white spirit or an ester or vegetable oil which is a plasticiser for PVC.
A marine antifouling agent containing at least either a compound represented by general formula (1) or a salt thereof as the active ingredient, wherein R¹ represents a lower alkyl group or a phenyl group which may be substituted by a halogen atom and/or a lower alkyl group; X¹ represents a halogen atom; n represents an integer of 1 to 5, provided when n is 2 or more, X's may be the same or different from one another; Y¹ represents a hydrogen atom or a group -Z-Y²; Z represents a carbonyl or sulfonyl group; and Y² represents an optionally substituted aryl group or a lower alkyl group. This agent is highly safe because of the use of the active ingredient comprising a compound other than organotin compounds, can prevent marine fouling organisms from depositing on ships, underwater constructions, fishnets and so forth even in a small dose, and exhibits a stable antifouling effect for long.