The disclosure is concerned with a composition of matter comprising an aqueous paste of a substantially monobasic tetrachloro or tetrabromphthalate salt in finely divided form as the dispersed phase and sufficient quantities of a dispersing agent and a thickener to prevent agglomeration and settling of the dispersed phase. Preferably the monobasic salt is one that is derived from a halophthalic acid or from a halophthalic anhydride by reaction with an alkaline base wherein the quantity of base used is from 0.7 to 1.2 equivalents of the base per mole of halophthalic acid or halophthalic anhydride. The quantity of the monobasic phthalic salt can comprise from 5 to 65% of the weight of the paste. The paste is useful for imparting enhanced flame resistance to wool.