Abstract: The present invention relates to a process for the recovery of gold and silver from the used refractory bricks of Dore furnace. This invention particularly relates to a process for the recovery of gold and silver from the used refractory bricks generated during the processing of the anode slimes of copper industry, through a non-cyanide route. The invention is useful for gold producing, gold refining and copper producing industries.

Abstract: A method for preparing ultra-pure silver from a crude silver halide matrix containing metallic and/or non-metallic impurities, said method comprising; roasting the crude silver halide matrix to substantially remove carbonaceous material; treating the roasted crude silver halide matrix with ammonium hydroxide to dissolve the silver halides and form an ammonium hydroxide reaction mixture; adding an initial reducing agent to the ammonium hydroxide reaction mixture to precipitate a crude silver powder mixture; separating the crude silver powder mixture from the ammonium hydroxide reaction mixture dissolving the crude silver powder mixture in nitric acid to form a crude silver nitrate solution; adding a first selective reducing agent to the crude silver nitrate solution to precipitate a silver/contaminant matrix and form a partially purified silver nitrate solution; separating the partially purified silver nitrate solution from the precipitated silver/contaminant matrix; adding a second selective reducing

Abstract: A process for making silver metal particles from silver salt particles having the same morphology. Precursor silver salt particles selected from the group consisting of silver acetate and silver sulfide having a selected morphology are contained in a reactor vessel having means for supporting the particles in an air suspension to prevent the agglomeration of the particles. Air is flowed through the reactor vessel at a flow rate sufficient to suspend the particles in the reactor vessel. The suspended precursor silver salt particles are heated to a processing temperature and at a heating rate below which the physical deterioration of the suspended precursor silver salt particles takes place. The suspended precursor silver salt particles are maintained at the processing temperature for a period of time sufficient to convert the particles into silver metal particles having the same morphology as the precursor silver salt particles.

Abstract: The present invention is concerned with a process for the direct smelting of zinc containing materials. The process includes volatilizing zinc from zinc-containing materials into a gas phase, while sulphur is fixed as iron sulphide in a Fe-S-O matte. Thereafter, zinc is recovered in metallic form with a suitable condenser apparatus from a zinc laden gas consisting of Zn(g), CO, CO.sub.2 and N.sub.2. Other metals like silver, cadmium, mercury and lead may also be recovered in this manner.

Abstract: A method of providing silver on a calcium carbonate material having fine pores, such as coral sand, oyster shells, and crab shells, including (a) contacting a calcium carbonate material with an aqueous solution of silver nitrate for a time effective for the silver nitrate to react with the calcium carbonate to form silver carbonate on the surface of the calcium carbonate material; (b) dewatering the calcium carbonate material after step (a); and (c) treating the calcium carbonate material after step (b) in an aqueous solution containing from 5 to 15 weight % of a reducing agent selected from the group consisting of ascorbic acid, a derivative of ascorbic acid, erythrobic acid, and a derivative of erythrobic acid to reduce the silver carbonate on the surface of the calcium carbonate to silver. Preferably contacting is by injection of an upward stream of the aqueous solution of silver nitrate through a layer of the calcium carbonate material.

Abstract: Apparatus for ultrasonic detection of flaws in the rail base of a track rail includes a sliding shoe having a transducer unit and coupling medium reservoir mounted thereon. The transducer, which is part of an ultrasonic testing system, transmits search signals into the rail base and receives associated reflected signals thereof. These signals, being capable of pictorially representing defects in the base of the rail, are monitored by the tester. The preferred embodiments allow for relative movement of the transducer unit and coupling medium reservoir along the base of the rail in order to provide for a succession of transmitted and reflected signals along the longitudinal extent of the rail base so as to test for flaws, defects, etc. in the same.