Abstract: An apparatus for the application of foam flux in a system for soldering printed boards, including a flux tank, a partition possessing a top portion rising above the fixed level of flux liquid and containing near the bottom portion thereof a perforated portion, serving to divide the interior of the flux tank into an inner tank portion and an outer tank portion, and a plurality of porous tubes disposed inside the inner tank portion having one end thereof communicating with an external compressed air feed mechanism and the other end thereof closed, the improvement wherein the porous tubes are porous ceramic tubes and are each obtained by molding an aggregate of uniform and fine ceramic-forming particles into the shape of a tube with the aid of an organic plasticizer and an inorganic binder and calcining, the porous tubes possessing pore diameters in the range of 10 to 30 microns and a porosity in the range of 35 to 55%.

Abstract: A filter, comprising in combination with a cartridge type filter element incorporating at least one cylindrical porous ceramic unit having a controlled pore diameter and a fixed wall thickness, opening at both ends and obtained by the steps of blending an aggregate of uniform, finely divided polyhedral particles of at least one kind of artificial raw material with an inorganic binder and an organic plasticizer, extrusion molding the resultant blend into a tube, and calcining the molded tube, which cylindrical porous ceramic unit is watertightly closed at one-end part thereof with an end plate and watertightly supported in place at the other-end part thereof with a bundling ring while the filtrate discharge duct defined by said cylindrical porous ceramic unit is allowed to form a filtrate discharge path; a case encircling said filter element; and a cover provided with a filtrate discharge path communicating with the empty space intervening between said case and said filter element, and adapted to seal tightly