Titanium has high resistance to oxidizing acids over a broad range of temperatures and concentrations. Standard acids in this group include nitric, perchloric, chromic, and hypochlorous (wet Cl 2) ...

THE importance of copper ions in natural redox systems is well known. For example, the oxidation of diphenols by molecular oxygen occurs by way of a Cu(I) to Cu(II) oxidation in the diphenol oxidase.