Abstract: A process for the manufacture of microfiltration membranes from aromatic polyamides, of which the pore sizes are between 0.05 and 10 .mu.m. A copolymer of isophthalic acid and m-phenylenediamine is dissolved in a solvent mixture of dimethylacetamide and dimethylformamide in the presence of alkali or alkaline earth chlorides and polyethyleneglycol. This solution is produced without the addition of water and is subsequently poured out onto a smooth surface formed of chemically inert material with the formation of the membranes. The water that is required as the precipitation agent, is only added to the poured-out solution by means of the air humidity. The relative air humidity is increased from 30% to 100% during formation of the membranes.

Abstract: The process for the visible marking of carrierless polymeric membranes for filtration purposes and for the reverse osmosis is characterized in that the marking symbols are first of all printed onto the casting support, onto which subsequently the casting mass is poured which serves for the production of the membrane. During the removing of the pre-solidified, solidified or finished membrane from the casting support, the printing dye which has an outline corresponding to the marking symbols, is taken up by the membrane and is taken along by the latter from the casting support. Preferably, the printing dye which had been imprinted onto the casting support when the membrane casting mass is poured on, has at least dried in a wipe-proof manner and, in this state, is soluble in the solvent-system of the membrane casting mass.

Abstract: A two-piece body high pressure membrane test cell is disclosed with a tangential feed into the interior pressure chamber in which a central distributor element is mounted with the lower frusto-conical end thereof at a critical spacing above a filter membrane. The membrane is supported on an annular land of a filter support disc which has a peripheral edge zone compressed in a sealed fit between the lower and upper pieces of the cell body. The edge zone is machined to a precise thickness to provide a reproducible and accurate spacing between the filter membrane that rests on the support and the lower end of the distributor.