Abstract: A high-speed silver plating solution for electroplating silver on a substrate which consists of a less-noble metal, such as copper, copper alloy, copper-plated base metal, iron, ferroalloy, nickel, or nickel alloy, characterized in that a cyclic compound whose ring includes a thioureylene radical ##STR1## (in which R.sub.1 and R.sub.2 are hydrogen or an alkyl or aryl group each) is added to the solution in a sufficient amount to prevent silver deposition by displacement reaction, whereby the silver deposition on the substrate is avoided. There is also provided a pretreating solution including the aforementioned compound for dipping the substrate prior to the silver plating.

Abstract: A process for rhenium recovery by the use of an anion exchange resin comprises eluting rhenium from the rhenium-adsorbed anion exchange resin with a hydrochloric acid solution containing a metal chloride. Preferred metal chloride is that of copper, cadmium, or zinc.

Abstract: Disclosed herein is a process for the selective removal of bismuth and/or antimony from an aqueous sulfuric acid solution containing dissolved bismuth and/or antimony mixed with other metals, such as an electrolyte formed in the electrolytic purification of metals, by which process bismuth and/or antimony are selectively removed from the above sulfuric acid solution by bringing said solution into contact with a phosphomethylamino chelate resin.

Abstract: A process for producing arsenous acid is disclosed. The reactants include an organic solvent containing 5 valent arsenic, a reducing agent and an additional component selected from the group consisting of water and an aqueous solution. The organic solvent containing 5 valent arsenic contacts and reacts with the reducing agent in the presence of the water or aqueous solution in order to directly produce arsenous acid from the organic solvent containing 5 valent arsenic. The process is a simple and economical process for producing arsenous acid.