Science and Celebrity: Humphry Davy's Rising Star

Davy using a voltaic battery to experiment with the decomposition of alkilis

Davy using a voltaic battery to experiment with the decomposition of alkilis

The June air was stifling. But in the Royal Society’s steeply raked amphitheater London’s fashionable men and women, scientists and laymen, crowded the benches and gallery to watch Humphry Davy, the celebrity chemist, present his latest scientific findings. The previous year at the Royal Society’s prestigious Bakerian Prize lecture, Davy had tossed a nugget of metallic potassium into a flask of water, where the lump skittered around the surface of the water before exploding in lavender flames. Expectations for the June lecture were high. The crowd leaned in, anticipating another colorful, if not explosive, performance. With his lively demonstration of electrolysis using a sizable voltaic pile, Davy did not disappoint.

The year 1808 was an important one for Humphry Davy. In that year two centuries ago, Davy discovered five elements: barium, calcium, boron, strontium, and magnesium. He delivered the news of his discoveries to rapt audiences in two captivating lectures—the first in June and another in December—that marked stepping stones in his climb to an apex of scientific and social celebrity status in London. But while Davy enjoyed his celebrity, he also bore gossip, speculation, and criticism as an outsider.

Davy’s 1808 discoveries depended on his use of and research into the burgeoning field of electrochemistry, the study of electricity’s effect on chemical reactions. As a young researcher at the Bristol Pneumatic Institute, Davy had caught the fever of excitement over Count Alessandro Volta’s 1800 paper describing what came to be known as the voltaic pile, a sandwich of a damp cardboard disk between two metal disks that generated a weak but continuous charge. Young Davy immediately began to study and experiment with voltaic piles, making batteries out of them, and using the electrical charges to separate elements from their compounds. Davy had contributed to the field by discovering that electricity itself was caused by chemistry. By the time he arrived in London in 1801, Davy had written six papers on his experiments in electrochemistry. In 1807, using electrochemistry, Davy isolated the metals potassium (from caustic potash, now known to be potassium hydroxide [KOH]) and sodium (from caustic soda, now known to be sodium hydroxide [NaOH]). In 1808 he isolated four of the alkaline earth metals from several mineral mixtures.

Davy’s electrolytic apparatus was simple in concept: a battery was connected to metallic electrodes that were dipped into a liquid containing the compound that Davy wanted to decompose into its elements. At first, Davy tried to dissolve various compounds in water, but the water was electrolyzed into hydrogen and oxygen, leaving the investigational compound intact. So Davy melted the minerals he was studying and then alloyed them with mercury before passing the electric current through them. The molten compounds bubbled when the current passed through, producing small clumps of silvery metals on one electrode and liberating gaseous oxygen on the other. The electrodes themselves were inert and did not react chemically with the electrolyte. Davy extracted pure barium from a substance called “baryte,” which may have been barium oxide (BaO) or barium sulfate (BaSO4). From “lime,” or calcium oxide (CaO), also known as quicklime, he prepared calcium. To isolate strontium he used “strontites,” which may have been a pure strontium oxide (SrO) or the strontium ore from the Strontian region of Scotland, composed primarily of strontium sulfate (SrSO4). Davy’s magnesium was isolated “magnesia,” or magnesium oxide (MgO).

Experiments as Entertainment

The late 1700s had witnessed the birth of the public scientific lecture, and by 1808 it had become a popular source of entertainment for London’s middle class and elite. Curious men and women would flock to lecture halls to watch as scientists demonstrated the latest discoveries about the properties of electricity, chemical elements, air, and gases. The demonstrations produced sparks, explosions, and unusual odors, all guaranteed to excite the audience. Davy was an expert at public demonstrations, showing off his own extra-ordinary discoveries and a flare for the theatrical that kept his audience riveted to their seats—and kept them talking about him long after they’d left the lecture hall.