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Today in History: William Crookes discovers thallium through flame spectroscopy

3/30/2026

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Story summary

On March 30, 1861, British chemist William Crookes announced his discovery of thallium, a chemical element identified through flame spectroscopy. This method revealed a distinctive green spectral line, leading to the element's name, derived from the Greek word for "green shoot." Crookes' work significantly advanced the field of analytical chemistry and spectroscopy.

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Story summary

On March 30, 1861, British chemist William Crookes announced his discovery of thallium, a chemical element identified through flame spectroscopy. This method revealed a distinctive green spectral line, leading to the element's name, derived from the Greek word for "green shoot." Crookes' work significantly advanced the field of analytical chemistry and spectroscopy.