Abstract: Waste materials containing chromium, such as the sludge resulting from neutralization of chromic acid bleed streams from metal cleaning and plating operations, are (1) rendered innocuous for land fill purposes by heating to temperatures of at least about 700.degree. C. to stabilize the materials for safe disposal and (2) activated by heating to temperatures of about 400.degree. to 500.degree. and the chromium content in the resulting calcine can be recovered by thermite reduction.

Abstract: Nickel powder of high surface area is produced by pressurized hydrogen reduction of an ammoniacal aqueous nickel sulfate solution using a small amount of a catalytic reductant compound exemplified by formaldehyde sulfoxalate (rongalite).

Abstract: Nickel and cobalt contained in aqueous sulfate solution are separately recovered by counter-current solvent extraction using a cobalt-selective organic extractant while scaling of equipment and cobalt recycle are minimized by controlling aqueous pH at the extraction, scrubbing and stripping stages to maximize cobalt loading and selectivity of the extractant while loading scale-causing ions such as calcium and magnesium in the extractant and removing them from the circuit with the aqueous cobalt strip solution.

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: A method is provided for enhancing the neutralization capability of high-magnesium serpentine silicate ore in the neutralization of nickel-containing pregnant leach solution, said solution having a pH of less than about 1 which comprises, providing said high magnesium serpentine ore in particulate form containing by weight over about 5% magnesium, roasting said ore under oxidizing conditions at a temperature below that temperature at which forsterite in said ore recrystallizes, and then adding an amount of said serpentine roasted ore to said pregnant liquor sufficient to raise the pH of the leach solution to a level above 2.

Abstract: Nickel is selectively leached efficiently and rapidly from Ni-Cu-Fe-S matte under oxidizing conditions at ordinary pressure by controlling in combination the following variables: (1) the acid-to-copper mole ratio in the leaching solution, (2) the temperature, and (3) the sulfur content of the matte, whereby an enriched nickel solution is obtained low in copper and iron.