Cadmium

Cadmium emerged from medical quality control: pharmacists in 19th-century Germany were selling impure zinc compounds to patients, and a government chemist discovered an unknown element hiding in the contamination. The discovery demonstrates how regulation can drive scientific discovery.

In 1817, Friedrich Stromeyer, professor of chemistry at the University of Göttingen and chief inspector of pharmacies in Hanover, was asked to investigate zinc oxide samples from Hildesheim pharmacies. Zinc oxide was commonly prescribed for skin conditions, and rumors had spread that patients were being poisoned by impure preparations.

Stromeyer noticed something peculiar. When he heated samples of zinc carbonate, they turned yellow-orange instead of the expected white of pure zinc oxide. The color suggested iron or lead contamination, but chemical tests found neither. He isolated and reduced the mysterious oxide, obtaining a bluish-white metal with properties distinct from any known element.

The discovery was convergent: three chemists—Stromeyer, Karl Samuel Leberecht Hermann, and Johann Christoph Heinrich Roloff—all discovered cadmium independently and nearly simultaneously. All three knew each other and were investigating the same problem: why certain zinc compounds behaved unexpectedly. Hermann initially suspected arsenic because of the yellow precipitate with hydrogen sulfide, but further analysis revealed the new element.

Stromeyer named the element from the Latin 'cadmia' and Greek 'kadmeia,' ancient names for calamine ore (zinc carbonate). The name thus connected the new element to its source material.

Cadmium proved commercially important for vivid yellow and orange pigments, electroplating, and eventually rechargeable batteries (nickel-cadmium). Artists prized cadmium yellow for its brilliance and permanence. But the element's toxicity—the same property that had raised concerns about zinc medicines—eventually limited its applications. Modern regulations restrict cadmium use, though nickel-cadmium batteries remain important in some applications.

The 1817 discovery belongs to a period when chemistry was transitioning from alchemy to modern science, and many discoveries came from pharmacists, apothecaries, and physicians investigating practical problems. Stromeyer's work exemplifies this: a regulatory inspection led to fundamental scientific discovery.