Abstract: The present invention is directed to an apparatus for preparing a lead or copper metal by electrolysis in a cell having a cathode and an anode which are separated by a diaphragm. The surface of the cathode is arranged in a substantially vertical direction and has a sufficiently low density of sites of nucleation so that metallic particles which are formed from the sites keep their individuality in relation to the adjacent particles, until the particles reach a dimension of at least 100 micrometers. An electrolyte is circulated between the cathode and an anode parallel to the surface of the cathode at a flow rate in a laminar to weakly turbulent manner so that under the action of the weight of the particles and the force exercised by the flow of the electrolyte the metallic particles are detached and fall into the electrolyte and are collected and are removed from the bottom of the cell.

Abstract: The invention relates to the treatment of purge solutions formed in the process of the extraction of zinc by electrolysis.According to the invention, the purge solution, which consists of a part of the purified solution rich in zinc sulfate, is subjected to electrodialysis in the presence of an anion exchange membrane so that a catholyte is formed which is depleted in zinc and in sulfate and which contains magnesium. The catholyte can then be precipitated by neutralization, after recovery of the remaining zinc.Application to the extraction of zinc from its ores.

Abstract: The invention relates to a process for removing nickel from lead chloride dissolved into chloride brine to obtain lead chloride solution wherein the nickel concentration is under 50 mg/liter. The present invention comprises the following steps:(a) adjusting the content of an element selected from the group of arsenic and antimony to a value of at least 1/5 of the concentration in nickel expressed in grams per liter;(b) contacting the solution from (a) with lead powder thus precipitating nickel and the said element selected from the group of arsenic and antimony.

Abstract: The present invention is a process for preparing a lead or copper metal by electrolysis in a cell having a cathode and an anode which are separated by a diaphragm, which comprises the steps of preparing an electrolyte containing a metal chloride to be prepared in at least one chloride of an alkali metal or alkaline-earth metal; circulating the electrolyte between the cathode and the anode parallel to the surface of the cathode, wherein the surface of the cathode is arranged in substantially a vertical direction and has a sufficiently low density of sites of nucleation so that the metallic particles which are formed from the sites keep their individuality in relation to the adjacent particles, until the particles reach a dimension of at least about 100 micrometers; maintaining the flow of the electrolyte along the length of the surface of the cathode in a laminary or weakly turbulent manner so that, under the action of their weight and of the forces exercised by the current of the electrolyte, the metallic par

Abstract: The invention relates to a process and a solvent for extraction of the chromates present in an aqueous solution. According to the invention, the aqueous phase is brought into contact with an organic phase comprising 2 to 10% by volume of a solvent selected from the group of tertiary or quaternary amines and 15 to 40% of a solvent selected from the group of esters of phosphoric acid in a diluent based on petroleum hydrocarbons. The invention is applicable to the production of concentrated solutions of chromates easily recyclable from an extraction of the chromates contained in an industrial solution.