December 26, 1898

Radium

Curie, Curie and Bémont propose the new element radium

The strongest fraction they had made was reported as 900 times more active than uranium — and it still consisted mostly of ordinary barium.

26 December 1898: a note read to the Academy

At the 26 December 1898 session of France's Académie des Sciences in Paris, Henri Becquerel presented a note by Pierre Curie, Marie Curie and Gustave Bémont. It described a strongly radioactive substance pulled from pitchblende that behaved chemically almost exactly like barium.

Repeated fractional separation made the barium-rich chlorides more radioactive, not less. Activity that started at 60 times that of metallic uranium climbed, through the separations, to 900 times that of uranium.

Three authors, and a spectral line from a fourth man

Gustave Bémont was a coauthor, not an assistant — the chemist who worked on separating the barium-like substance. Popular accounts routinely drop him and leave only Marie and Pierre.

Eugène Demarçay, who was not an author at all, supplied independent spectral evidence. He had seen an unfamiliar spectral line in the material, and it strengthened in step with the radioactivity; together with the fractionation results, that supported the hypothesis of an unknown element rather than unusually active barium.

What the paper did not claim

The language was deliberately provisional. The authors concluded that the substance appeared to contain a new element and proposed the name radium; they did not claim to have isolated it.

The 1898 material was overwhelmingly barium, and the name plus the supporting evidence was all that entered the Academy's published record that day. Proving radium's chemical individuality and isolating it required several more years.

Sources

Researched 23 Aug 2026 6 sources 2 audit passes

How this was checked

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What the sources leave uncertain

December 26 is securely documented as the Académie des Sciences session date. December 21, sometimes given as the laboratory discovery date, is a separate milestone reconstructed from laboratory records and should not replace the announcement date.
The 1898 material was overwhelmingly barium. The paper’s language was explicitly provisional: it said the substance appeared to contain a new element.