Abstract: A cell filter having a series of filtering cells and a distributor for collecting and adjusting the distribution of fluids passing through the cell filtering surface. Each cell has a planar filtering bed composed of a filtering cloth bearing on a rigid apertured support. Fluid passes through the cloth onto the cell bottom which slants toward a drain channel. The drain channel slants toward a discharge duct connected to a distributor. Guide members in the distributor fractionate, divide, and direct the fluid flowing towards the discharge duct into two parallel adjacent streams. The guide members are a series of baffle plates, located along the top length of the drain channel. The baffle plates are slanted, the plate farthest from the low end of the drain channel having the steepest slant.

Abstract: The present invention relates to a process for treating residues from a primary leaching of ferriferous zinc ores by sulphuric acid, with a view to recover a leadbearing by-product, such process comprising a secondary leaching of said residues, by sulphuric acid, within several countercurrent stages, at a temperature comprised between 85.degree. and 100.degree. C., the solid residues of the successive stages being circulated from the first to the last stage, the residue of this last stage being the said lead bearing by-product, whereas the various solutions separated from the second to the last stage are each recycled within the leaching operation of the respectively foregoing stage, and the dual zinc and iron sulphates solution, as separated from the first stage, being the principal product of the treatment.

Abstract: A multi-compartment reaction system for the manufacture of phosphoric acid by the wet process having a recirculation slurry flash cooler. The removal of heat from the reaction system is accomplished by circulating reaction zone slurry through an elevated vacuum flash cooler under the combined effect of differential liquid levels maintained in the system, and the vacuum in the flash cooler. The amount of reaction zone slurry passed to the flash cooler is sufficiently large so that the temperature differential experienced by the slurry is low and crystallization of calcium sulfate from the slurry liquid occurs in a favorable manner. There is also a substantial reduction in the pumping requirements compared with conventional operations in which the slurry is pumped to an elevated flash cooler, even though the large amount of slurry is passed to the flash cooler in accordance with the invention.

Abstract: Process for purifying an iron containing zinc sulfate solution which comprises precipitating iron from said solution as a slurry in at least one of the following forms at a pH which is maintained lower than 4: basic sulfate, jarosite or goethite; filtering said slurry on a planar horizontal filter and forming a cake on said planar filter; washing the cake directly on the planar filter with water supplied onto the cake without forming a newslurry with washing water and thus freeing the cake from water soluble zinc and copper compounds promptly before hydrolysis thereof insolubilizes said compounds as basic sulfates, whereby the solid residue in the cake does not contain substantially more insoluble zinc content than it contained in the slurry being fed to the filtration.

Abstract: A cell filter having a collecting part divided into chambers and compartments and provided with cavities. Each compartment is provided on the one hand at the bottom thereof with at least one liquid-discharge outlet lying substantially below that level where the cavities open and on the other hand, above the liquid top level, with at least one passageway towards a gas-sucking device in such a way as to suck the gases while causing the gases and liquids to separate and go along different paths inside the compartments, means being provided to return to the original compartment those liquids which might have entered the passageways so as on the one hand, obtain at the distributor outlet, liquid-free gases and on the other hand, collect through the discharge openings only liquids which are substantially free from undissolved gases.

Abstract: An iron oxide based pigment in alpha-Fe.sub.2 O.sub.3 form, which contains the water insoluble part obtained by calcination of basic iron sulfate and/or jarosite based residues, this pigment being prepared by a process comprising calcining at a temperature from 600.degree. to 800.degree. C and during a period from 2 to 240 minutes basic iron sulfate and/or jarosite based residues, so as to decompose in an incomplete manner such basic iron sulfates and/or jarosite and to obtain in the calcined product an iron bonded sulfur content of more than 0.6%, and solubilizing the not decomposed iron sulfates with other soluble sulfated metals, such as zinc sulfate, by lixiviating the calcined product, these water-soluble compounds being then separated by appropriate processes.

Abstract: A method for purifying phosphoric acid obtained with sulfuric acid acting on natural phosphates, comprises extracting the phosphoric acid with a mixed solvent formed essentially by 95% to 50% by volume of an ether containing 5 to 7 carbon atoms, and by 5% to 50% by volume of at least one of the esters resulting from the reaction of the phosphoric acid with alcohols having 3 to 5 carbon atoms.