Group 3 element it from pitchblende residues left by Marie and Pierre Curie after they had extracted radium. In 1899, Debierne described the substance as similar to titanium and (in 1900) as similar to thorium. Friedrich Oskar Giesel independently discovered actinium in 1902 as a substance being similar to lanthanum and called it "emanium" in 1904. After a comparison of the substances half-lives determined by Debierne, Hariett Brooks in 1904, and Otto Hahn and Otto Sackur in 1905, Debierne's chosen name for the new element was retained because it had seniority, despite the contradicting chemical properties he claimed for the element at different
Depleted uranium Depleted uranium has been used in a number of sampling calorimeters (such as in the D0 and ZEUS detectors) due to its high density and natural radioactivity. Normal functioning of the kidney, brain, liver, heart, and numerous other systems can be affected by uranium exposure because, in addition to being weakly radioactive, uranium is a toxic metal, although less toxic than other heavy metals, such as arsenic and mercury. It is weakly radioactive but is 'persistently' so because of its long half-life. The Agency for Toxic Substances and Disease Registry states that: "to be exposed to radiation from uranium, you