Abstract: An aqueous solution for obtaining a noble metal by chemical reduction containing at least one water-soluble compound or complex of a metal selected from the group consisting of gold, platinum, silver, and palladium as a source of the metal to be deposited, and at least one mercapto compound or sulfide compound or a salt thereof as a reducing agent. The reducing agent is typically mercaptoacetic acid, 2-mercaptopropionic acid, 2-aminoethanethiol, 2-mercaptoethanol, glucose cysteine, 1-thioglycerol, sodium mercaptopropanesulfonate, N-acetylmethionine, thiosalicylic acid, 2-thiazoline-2-thiol, 2,5-dimercapto-1,3,4-thiadiazole, 2-benzothiazolethiol, or 2-benzimidazolethiol. They may be used singly or in combination.

Abstract: An aqueous solution for the reductive deposition of metals comprising, besides water, (A) a phosphine of the general formula (1)  in which R1, R2, and R3 denote lower alkyl groups, at least one of which being hydroxy-or amino-substituted lower alkyl group, and (B) a soluble compound of a metal or a compound of a metal solubilized through the formation of a soluble complex by said phosphine.