Behavior of nickel, cobalt, iron, magnesium in autoclave leaching of oxidated nickel ore, using elementary sulphur as oxidated reagent instead of conventionally used sulphuric acid has been researched. Preliminary sulphidation at 190 ^oC temperature during 1 hour is necessary for obtaining a high level of nickel and cobalt extraction in solution via leaching (>95% Ni, >90% Co). The scheme, wherein important chain loop of elementary acts of sulphide formation is polymerous sulphur (S_x), has been proposed on the base of analysis of literature data in area of physical and chemical properties of sulphur, depending on molecular structure of sulphur and S—H₂O system.