Henry Cavendish (1731–1810): Hydrogen, Carbon Dioxide, Water, and Weighing the World

Abstract

Henry Cavendish (1731–1810) was an outstanding chemist and physicist. Although he was not a major figure in the history of respiratory physiology he made important discoveries concerning hydrogen, carbon dioxide, atmospheric air, and water. Hydrogen had been prepared earlier by Boyle but its properties had not been recognized and Cavendish described these in detail including the density of the gas. Carbon dioxide had also previously been studied by Black but Cavendish clarified its properties and measured its density. He was the first person to accurately analyze atmospheric air and reported that the oxygen concentration was very close to the currently accepted value. When he removed all the oxygen and nitrogen from an air sample, he found that there was a residual portion of about 0.8 % which he could not characterize. Later this was shown to be argon. He produced large amounts of water by burning hydrogen in oxygen and recognized that these were its only constituents. Cavendish also worked on electricity and heat. However his main contribution outside chemistry was an audacious experiment to measure the density of the earth which he referred to as “weighing the world”. This involved determining the gravitational attraction between lead spheres in a specially constructed building. Although this was a simple experiment in principle, there were numerous complexities which he overcame with meticulous attention to experimental details. His result was very close to the modern accepted value. The Cavendish Experiment as it is called assures his place in the history of science.