low molecular weight hydrolyzed polymers or copolymers of the general structure : ## str1 ## exhibit excellent depressive action in the flotation of non - sulfide mineral ores thereby resulting in improved selectivity and recovery . the low molecular weight , partially hydrolyzed polymers or copolymers perform depressing action without resulting in any associated flocculation in the flotation system . the partially hydrolyzed polymers or copolymers can be combined with other known depressing agents for non - sulfide ores , such as starch , dextrin , gum and the like , to obtain equivalent or improved selectivity and recovery than would be obtained using these depressants alone .