Palladium. Samples of the transition metal palladium (Pd). Palladium is a rare silver-white metal in the platinum group. It is often used in chemistry as a catalyst, especially in hydrogenation and dehydrogenation reactions. It can also be alloyed with gold to produce white gold., Image: 129136706, License: Rights-managed, Restrictions: , Model Release: no, Credit line: Profimedia, Sciencephoto RM