Alessandro Giuseppi Volta

1745-1827

Italian Physicist

It is a mark of Alessandro Volta's influence on the world of science that the international unit of electrical potential difference or force is named the volt in his honor. His development of the first battery in 1800, along with his other experiments involving electrical current, made Volta a lasting name; however, he also conducted important studies with chemicals and gases.

Volta was born on February 18, 1745, in the town of Como in Italy's Lombardy region. He was one of nine children, and most of the others went on to pursue careers in the church, but after reading an essay by Joseph Priestley (1733-1804) at age 14, Volta decided to become a physicist.

By 1774, the 29-year-old Volta had been appointed professor of physics at the high school in Como. While working in this position, he developed his electrophorus, an early type of condenser for storing electrical charges. Volta's electrophorus made use of the earlier discovery by Charles-Augustine de Coulomb (1736-1806) that electrical charges are generated at the surface of a body rather than in its interior.

Also during the mid-1770s, Volta became involved in chemical experimentation. He discovered methane gas while studying marsh gas in 1776, and later made the first accurate measurements of the proportion of oxygen in the air. By this point his reputation had been growing, thanks in large part to the electrophorus, and in 1779 he became a professor at the University of Pavia. He soon set to work creating an electrometer for measuring electrical currents, and spent much of the 1780s in electrical experimentation.

In 1791, however, Volta was drawn into a curious controversy arising from claims made by his fellow Italian physicist Luigi Galvani (1737-1798). Galvani had noted that when he touched a frog's legs with probes of differing metallic composition, the muscles twitched, and this he attributed to what he called "animal electricity." Volta suspected these claims, and over a long series of experiments—some of which required him to be the subject—he showed that the electrical charge came from the two types of metal probes, not from anything inside the frog.

Continuing his earlier chemical experiments, Volta in 1796 found that the pressure of a chemical results from its temperature, not from pressure in the surrounding atmosphere. There was an ultimate purpose to his dual experiments in chemistry and physics, and this became clear in 1800, when he created the first battery. He did this by filling bowls with a saline solution and connecting them with a wire, one end of which was copper and the other zinc or tin.

Volta soon experimented with making a smaller battery, using stacks of copper, zinc, and cardboard soaked in a saline solution and connected by a wire. The stack was called a Voltaic pile. Later in 1800, English chemist William Nicholson (1753-1815) used a Voltaic pile to separate hydrogen from oxygen in water—the first use of electrolysis.

The work with batteries and Voltaic piles marked the zenith of Volta's career. He died on March 5, 1827, at the age of 82.

JUDSON KNIGHT