Abstract: A cylindrical electrostatic oil cleaner is provided for removing dust from an insulating liquid. The cleaner is constructed of a cylindrical receptacle, a plurality of cylindrical positive and negative electrode plates and insulating dust collectors. The positive and negative electrode plates are coaxially arranged in an opposing relationship within the receptacle, so that an innermost compartment is defined in a form surrounded by the innermost electrode plate and outer compartments are defined between the respective electrode plates. The insulating dust collectors are arranged in the innermost and outer compartments, respectively. Each of the dust collectors comprises a plurality of cylindrical collector elements which individually form a corrugated zigzag peripheral wall.

Abstract: A method for extracting and removing water-soluble substances from a non-water-soluble fluid containing water-soluble substances by using water or an aqueous solution as the extractant and bringing the non-water-soluble fluid and the water or aqueous solution into contact with each other by means of filters.