A neutron activation method, involving a radiochemical separation based upon two consecutive distillations, is described for the direct determination of nanogram amounts of osmium and ruthenium in selected sulphide ores. A loss of osmium due to volatilization occurred when the tracer solution was evaporated. A simple radiochemical method using iron(III) hydroxide precipitation was devised to prevent this loss. The proposed method was applied to ores expected to contain only traces of platinum metals. The addition of the active carrier was found to improve the separation of these two metals in the submicrogram range, although, no chemical yield determination was necessary. © 1968.