Explanatory notes
… a sheet, membrane or mass of porous material (e.g., cloth, felt, wire‑cloth, skin, stoneware, porcelain, kieselguhr, … permanent magnets or electromagnets for the extraction of ferrous particles from the oil. (4) Filters for boiler water … to a common vacuum line. The filter is submerged in the feed tank and the vacuum applied. (8) Chemical water …