Abstract: Ultrafine cobalt and nickel powders are produced from sulfate solutions containing ammonia under hydrogen pressure in the presence of a small amount of a reductant from the group consisting of metal hydrides, metal borohydrides and metal borides. Cobalt powders having a particle size of about 2 micrometers produced in accordance with the invention have been used successfully in the production of cobalt-cemented tungsten carbide.

Abstract: The scaling of autoclave and leaching-equipment surfaces during the high pressure leaching of nickeliferous oxide and silicate ores is controlled during leaching to favor the formation of scale containing substantial amounts of magnesium sulfate that is more easily removed by chemical dissolution using water or dilute sulfuric acid at temperatures ranging from about 50.degree. C. to 250.degree. C. than scale containing substantial amounts of alunite.

Abstract: A method is provided for inhibiting the formation of silica scale on flash-pot surfaces during the multi-stage flashing of sulfuric acid pressure-leach slurry obtained following the continuous autoclave leaching of nickel lateritic ore at elevated temperature and pressure during which silica is dissolved, wherein the leach slurry is subjected to a high-temperature flash stage such that the slurry at the flash temperature is supersaturated in soluble silica, and wherein the slurry is thereafter subjected to at least one additional flash at an intermediate-temperature flash stage at which silica precipitates and tends to form a scale accompanied by a decrease in said supersaturation.