ligands will be readily apparent to one of skill in the art illustrative of such other equivalent ligands are aminopolycarboxylic acids such as 1 2 diaminocyclohexane tetraacetic acid and diethylenetriaminopentaacetic acid 8 hydroxyquinoline or substituted 8 hydroxyquinolines such as 8 hydroxyquinoline 5 sulfonic acid in addition to the dipositive chromium complexed with polydentate ligands illustrated above the invention contemplates as full equivalents polydentate ligand complexes of dipositive vanadium and of dipositive titanium prepared and used in analogous fashion to the preparation and use of dipositive chromium complexes to prepare the edta chromium complex or the other metal liquid complexes contemplated as equivalent by the invention to an appropriate concentration of a desired chromium vanadium or titanium salt in water may be added a desired molar equivalent of ethylene diamine tetraacetic acid or a salt thereof or a water soluble form of any of the other polydentate complexing agents contemplated as equivalent by the invention at an elevated temperature and with agitation until conductivity measurements indicate that complexation is complete the concentration of the polydentate ligand complex of chromium vanadium or titanium may vary within wide limits the concentration may range from minimal to the upper limit of solubility of the complex preferably from about 0 1 millimole mm per liter to about 100 mm per liter most preferably from about 2 0 mm per liter to about 5 0 mm per liter the water soluble salt of chromium vanadium or titanium employed may be a salt of any convenient anion for use in a typical paper mill sulfate salts will be preferred for obvious reasons the ph range for the practice of.