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.