Forms of palladium released under crystallization of the Fe-Ni-S system sulfide melts at a sulfur content of 40-51 at%.

Synthesis of the Fe-Ni-S system from a melt and its subsequent annealing at 800 and 600 degrees C permitted a detailed study of its inner part (40-51% at.% S) containing 1 wt.% Pd. As the content of S and the Ni:Fe ratio in the Fe-Ni-S system increase, the predominant forms of palladium successively change from <<ferropalladium>>, via Pd-containing sulfides (pentlandite, heazlewoodite solid solution), to palladium sulfides containing Ni and Fe (Pd,Ni,Fe)S and (Pd,Ni,Fe)(16)S-7. It has been established that at the high-temperature stage of sulfide melt crystallization Pd may accumulate in the crystal lattice of heazlewoodite solid solution with subsequent separation concentrates into pentlandite. The Pd content in this pentlandite, which is the product of peritectoid interaction of Hzss and Mss, varies within 0.1-3 at. %. The maximum Pd content of 5.8 at. % is found in Ni-pentlandites formed in the S-Mss decomposition. At high temperatures (600 degrees C and higher), the solubility of Pd in the S-enriched monosulfide solid solution reaches 0.4 at.%.