X-ray studies indicate that mixed iron and nickel “amalgams” are reactive even at room temperature. By distilling off the mercury from these amalgams at temperatures between 400 and 100°C, ultrafine iron-nickel alloy powders are readily obtained. X-ray studies show that these powders possess equilibrium structures corresponding to the temperature of preparation. Alloy powders belonging to many alloy systems and having controlled composition, purity, and particle size may be prepared by this process. One special use of the process is in the preparation of homogeneous alloy powders for studying solid state equilibria below 400°C, particularly in alloy systems with sluggish transformations, the process being invaluable in the temperature range between 200 and 100°C, Another is in the preparation of ultrafine metal and alloy powders with equally fine, if not finer, dispersions of other phases, suited for studying dispersion-strengthening. Both of these special uses are currently under investigation,