Uranium in the form of the mineral pitchblende (Uranium Oxide) often turned up in the Middle Ages in Silver Mines of Joachimsthal (now part of the Czech Republic, but then the Kingdom of Bohemia) and was thought to contain zinc or iron. Its name pitchblende was derived from pech, meaning pitch (or ill/bad luck), and blende, meaning deceiver.

Then, in 1789, Martin Heinrich Klaproth, a pharmacist who had his own experimental laboratory in Berlin, Germany, investigated pitchblende and found that it dissolved in nitric acid and precipitated a yellow compound when the solution was neutralized with sodium hydroxide (184). He was convinced that that it was the oxide of an unknown element and when he heated the precipitate with charcoal and obtained a black powder, he assumed he had produced the metal itself. He therefore based its name on the newly discoved planet Uranus and gave it the name "uran," which later became uranium.

Later tests showed that Klaproth's metal was in fact one of the oxides of uranium, and it fell to Eugene Peligot, who was professor of Analytical Chemistry at the Central School of Arts and Manufactures, in Paris, to isolate the first sample of uranium metal, which he did in 1841 by heating uranium tetrachloride with potassium.

For the better part of the nineteenth century, uranium was not regarded as particularly dangerous and commercial and practical uses were found for it.

The discovery that uranium was radioactive came only in 1896 by accident when Henri Becquerel in Paris found that a sample of uranium left in a drawer on top of an unexposed piece of photographic plate caused the plate to become "fogged," as if it had been partly exposed to light. From that he deduced that uranium was emitting invisible rays.

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