Abstract: A polishing composition comprising the following components:(a) an abrasive,(b) an oxidizing agent capable of oxidizing tantalum,(c) a reducing agent capable of reducing tantalum oxide, and(d) water.

Abstract: A mold positioning apparatus which is used in a pressing apparatus for pressing a work by a plunger and a bottom mold, comprising keys and key guides which are provided on a plunger and a bottom mold, and which are engaged together to restrict a relative position between the plunger and the bottom mold; means for shaking at least one of the plunger and the bottom mold in clearance between the key and the key guide while keeping the key and the key guide in engagement; means for measuring a movable range of the at least one of the plunger and the bottom mold during the shaking; a device for calculating a relative position between the key and the key guide and the relative position between the plunger and the bottom mold based on the measured movable range; and means for adjusting the plunger and the bottom mold in a range of the clearance of the key and the key guide based on the calculation to carry out positioning therebetween.