The present invention is generally directed to removing a trace element from a liquid hydrocarbon feed. The liquid hydrocarbon feed, containing the trace element, is mixed with the water along with a hydrocarbon-soluble additive. While being mixed, a compound, which in some cases is preferably insoluble, is formed by the hydrocarbon-soluble additive chemically reacting with the trace element. A phase separation device, such as a desalter or an oil-water separator, receives the oil-water emulsion containing the compound and resolves the mixture to produce the compound, effluent brine, and effluent liquid hydrocarbon with a reduced concentration of the trace element as compared to the liquid hydrocarbon feed. In some embodiments, the present invention is directed to removing elemental mercury from a liquid hydrocarbon feed. A hydrocarbon-soluble sulfur-containing additive, typically an organic polysulfide, is mixed with the liquid hydrocarbon feed and water. The hydrocarbon-soluble, sulfur-containing additive reacts with the mercury, rapidly forming an agglomeration of mercuric sulfide which is then dispensed with the effluent brine or the effluent liquid hydrocarbon.