Abstract: A joint of a member joined by joining apparatus is tested by detecting an area of the joint and checking if the area has a predetermined value or not. A test apparatus includes an imaging device for imaging the joint on an image plane and converting the image to an electric signal and a processor for extracting the area of the joint from the electric signal from the imaging means to test the joint.

Abstract: From a ruthenium-containing substance, sparingly soluble in any of water, acid solutions and basic solutions, flaked off used metal electrodes comprising a substrate of a corrosion-resistant metal coated with ruthenium metal or a compound thereof, ruthenium is recovered in the form of metal or a compound thereof, soluble in such media as described hereabove, easily and with a high percent recovery by means of a combination of simple chemical procedures and also inexpensive chemicals and in a short period of time. The recovered ruthenium metal or compound thereof can be reused for recoating used metal electrodes and the like.