Abstract: A method of preparing cells for the purpose of enabling one fluid to be affected by another fluid via thin membranes of inorganic artificial fibres, which membranes are corrugated all over or in part and caused to bear upon each other along discrete lines of contact so as to form through passages or compartments for the fluids. The cell is constructed of membranes of artificial fibres which have a filament diameter of at least 3 and at most 20 micrometers and are elastic. The fibres are loosely matted so that when the spaces between the fibres in the assembled cell have been filled with a fine powder which is bound with an inorganic binder the powder forms a load-bearing layer which is cohesive throughout the surface extension of the membrane and through its cross-section and in which the fibres act as reinforcement.