English chemist who experimented with gases by inhaling them. This experimental procedure nearly proved fatal on several occasions, but led to the discovery of the unusual effects of nitrous oxide, which came to be known as laughing gas. He performed the first electrochemical decompositions, isolating potassium, barium, strontium, calcium, and magnesium. Davy showed that hydrochloric acid did not contain oxygen, in opposition to Lavoisier's theories. He proved that chlorine was an element, and gave it its name (derived from the Greek work for green). Davy was a popular lecturer and able experimenter. In fact, it was as an assistant in Davy's lab that Faraday began his scientific career.

One of Davy's experiments consisted of rubbing two ice cubes together and observing that they melted, in contradiction to the caloric theory. Davy also proposed a system of proportions to calculate ratios of chemical combination similar to the "chemical equivalents" of Wollaston. He showed that a voltaic pile produced no current when the disks were wetted with pure water. He also showed that electrical conductivity is proportional to surface area over length, but independent of cross-sectional shape, proving that current passes through the interior. He also found that electrical conductivity of metals varied with temperature, being lower for higher temperature.

Lavoisier, Wollaston