Abstract: A process is described for the removal of one or more heavy metals from an aqueous system containing at least two heavy metals by the addition of a soluble sulfide to precipitate at least one of said heavy metals as the sulfide thereof, which comprises adding an amount of soluble sulfide statistically determined to be sufficient to precipitate as the sulfide substantially all of at least one heavy metal to the limits of its metal sulfide solubility; said statistically determined amount of soluble sulfide being less than the amount required to precipitate as the metal sulfide at least one other heavy metal in said system having a soluble sulfide equilibrium concentration sufficiently higher than that of said selected heavy metal to thus permit selective precipitation of said selected metal and of any other heavy metals present having lower sulfide equilibrium solubility concentrations than that of the selected heavy metal, wtih said precipitation being to the limits of the metal sulfide solubilities; and preci