Abstract: Disclosed is an oil separating method in which oil-contaminated water in a separation tank is mixed with air bubbles in a bubble-generating apparatus provided at the bottom of the separation tank to jet out said air-water mixture into the separation tank,wherein a surfactant and/or an antifoamer are(is) previously added to the oil-contaminated water.

Abstract: A technique of holding an object, wherein an object (10) to be held is placed on a holding surface (3) having a plurality of suction holes (4), each of which has a valve (6) therein which is operated in accordance with the difference between the pressure in the upper or outer space and the pressure in the lower or inner space demarcated by the valve (6). The valve (6) is opened by utilizing the phenomena that such pressure difference in those suction holes (4) closed by the object (10) becomes smaller, whereas the valves (6) are closed by utilizing the phenomena that such pressure difference in those suction holes (4) which are not closed by the object (10) and remain open becomes greater, to thereby prevent reduction of the suction force to be exerted on the object (10).

Abstract: A technique of holding an object, wherein an object (10) to be held is placed on a holding surface (3) having a plurality of suction holes (4), each of which has a valve (6) therein which is operated in accordance with the difference between the pressure in the upper or outer space and the pressure in the lower or inner space demarcated by the valve (6). The valve (6) is opened by utilizing the phenomena that such pressure difference in those suction holes (4) closed by the object (10) becomes smaller, whereas the valves (6) are closed by utilizing the phenomena that such pressure difference in those suction holes (4) which are not closed by the object (10) and remain open becomes greater, to thereby prevent reduction of the suction force to be exerted on the object (10).