Abstract: The present invention provides a palladium-base electroless plating solution which is excellent in stability and which is capable of forming a satisfactory palladium-base deposit, the solution being an aqueous solution containing (a) a palladium compound, (b) at least one compound of ammonia and amine compounds, (c) an organic compound containing bivalent sulfur, and (d) at least one compound of hypophosphorous acid compounds and boron hydride compounds, and a palladium-base electroless plating solution containing a nickel compound in addition to said electroless plating solution.

Abstract: An electroless copper plating bath is prepared by adding both a metal-cyano-complex used as a stabilizer and an agent for complexing the metal of the metal-cyano-complex to an electroless copper plating bath containing cupric ion, an agent for complexing the cupric ion and a reducing agent, and an article to be plated is immersed in the bath.

Abstract: An analytical method for determining by potentiometric titration formaldehyde in an electroless copper plating bath, which comprises using a hydroxylamine salt such as hydroxylamine hydrochloride as the titrant and using a silver electrode as the indicator electrode. This method can determine free formaldehyde in low concentration which takes part in the plating reaction.

Abstract: A vibratory plating method carried out by placing only workpieces and a plating liquid in a plating container, and applying an electric current across the plating liquid while vibrating the plating container so as to cause the workpieces to be plated as the workpieces are rolled and moved independently of one another along the plating container. By this plating method, workpieces can be plated uniformly in a very short period of time at a high current density and with a small amount of plating liquid. Moreover, it eliminates troublesome steps of manually suspending and removing workpieces from hangers.

Abstract: A vibratory plating apparatus having a plating liquid in a plating container, a base on which the container is mounted for vibrating movement, and a lid for the top of the container. The bottom of the container has an arcuate bottom. A vibration motor vibrates the container and electrodes are disposed within the container. With this plating apparatus, workpieces can be plated uniformly in a very short period of time at a high current density and with a small amount of plating liquid. Moreover, it eliminates troublesome steps of manually suspending and removing workpieces from hangers.

Abstract: A sludge containing a sparingly soluble metal compound such as nickel carbonate or the like is supplied to an anode compartment or an intermediate compartment of an electrolytic cell provided with an anode compartment and a cathode compartment or with an anode compartment, an intermediate compartment and a cathode compartment each sectioned by a filter membrane or an ion-exchange membrane, and thereafter an electrolytic treatment is conducted by using an insoluble electrode as anode and a usual electrode as cathode to precipitate a metal such as nickel on the cathode. Effective recovery of a metal is attained directly from a sludge by way of electrolysis.