Alessandro Volta

Italian physicist

• Born: February 18, 1745
• Birthplace: Como, Duchy of Milan (now in Italy)
• Died: March 5, 1827
• Place of death: Como, Kingdom of Lombardy-Venetia (now in Italy)

Volta contributed to the development of concepts and techniques in electrostatics, including the inventions of the electrophorus and the condensing electrometer. His most important contributions were the discovery of contact electricity and the invention of the electric battery.

Early Life

Alessandro Volta (ah-lays-SAHN-droh VAWL-tah) was the youngest of nine children born to Filippo and Maddalena Volta in the ancient Roman town of Como, on Lake Como in what is now northern Italy. His father was a member of the Jesuit order for eleven years before withdrawing to wed Maddalena dei Conti Inzaghi, who was twenty-two years younger than he. Although Volta’s family was from the local nobility, his father had spent the family fortune and gone into debt before Alessandro’s birth. Three of his brothers became priests, and two of his sisters became nuns. Throughout his life, he was active in the Catholic religion.

Although Volta did not talk until he was four, he began to excel early in school and showed special ability in foreign languages. When Volta was about seven years old, his father died, but with the aid of his two uncles he attended the local Jesuit college, where attempts were made to recruit him to the priesthood. After completing the classical course of education at the age of sixteen, Volta continued his education until 1765 at the Seminario Benzi, where he was attracted to the natural sciences. There he wrote a long Latin poem of some five hundred verses, mostly celebrating the work of the English chemistJoseph Priestley, who later wrote a two-volume history of electricity.

By the age of eighteen, Volta had decided to devote himself to the study of electricity. In 1763, he began a correspondence with the eminent French electrical scientist l’Abbé Jean-Antoine Nollet. In these letters, he supported Roger Joseph Boscovich in suggesting that electrical attraction followed the Newtonian concept of action at a distance instead of the direct emission and absorption of electrical effluvia as taught by Nollet. He also began an experimental study of electricity, with equipment and laboratory facilities provided by his friend and benefactor Giulio Gattoni. After learning of Benjamin Franklin’s work, Volta and Gattoni constructed the first lightning rod in Como and studied the electricity collected by it. Volta’s concentration on his work was so great that he often missed meals, slept little, and was unaware of the condition of his clothing. He soon developed a genius for inventing inexpensive but effective apparatuses, which led to a successful career.

Life’s Work

Volta’s research in static electricity was the foundation for his later invention of the electric battery. The first results of his work were sent in 1765 to Giovanni Beccaria, professor of physics at the University of Turin and the leading Italian electrical scientist. In a series of letters, Volta described his design of a machine to produce electrostatic effects and reported on which materials would become positive and which negative when rubbed together. Volta’s correspondence with Beccaria led to Volta’s first publication, De vi attractiva ignis electrici (1769; on the attractive force of electric fire). This seventy-two-page treatise boldly reinterpreted Beccaria’s experiments and Franklin’s theory of a self-repulsive electrical fluid in terms of a consistent principle of attraction. In this book and a second book in 1771, Volta remained faithful to Franklin’s theory of a single electric fluid but suggested that all materials are in electrical equilibrium until disturbed by frictional activity.

Volta was appointed to his first academic post in 1774 as principal of the state school in Como, previously under Jesuit control. He was a large and vigorous man, with wide social contacts. In 1775, he sent a letter to Priestley, announcing the invention of his electrophorus, which he viewed as a kind of perpetual source of electrical fluid. This device consisted of a flat insulating cake made of three parts turpentine, two parts resin, and one part wax, hardened in a metal dish and covered by a metal plate with an insulated handle. After the cake has been rubbed, the plate can be set on it and briefly touched to transfer electrical fluid by induction. The plate thus charged can be lifted and discharged into a Leyden jar to store it; the operation can be repeated many times. The device became very popular, and its induction process reinforced Volta’s emphasis on action at a distance and the similar ideas of Franz Aepinus. With his increasing fame, Volta was able to shift from administrator to professor of experimental physics without the usual examination.

Volta’s interests expanded into chemistry in 1778, with his discovery of inflammable marsh gas, now called methane, in Lake Maggiore. He collected this gas from bubbles rising to the surface, especially in shallow, marshy locations. He used his electrophorus to ignite the gas from the discharge of a spark in what he called an electric pistol and correctly explained its source as decaying animal and vegetable matter. Similar experiments with hydrogen led to measurements of the contraction of air when exploded with an equal volume of hydrogen in his eudiometer, giving a total reduction of 3/5. This corresponds to a 1/5 contraction of air, consistent with later measurements of the oxygen content.

In a famous letter written in 1777, Volta proposed an electric signal line from Como to Milan, on which a Leyden jar could be discharged at one end, causing the detonation of an electric pistol at the other end. His increasing fame led to a state-supported trip to some of the chief science centers of Europe and a new position in 1778 as professor of experimental physics at the University of Pavia. During nearly forty years in this position, Volta was able to obtain an excellent collection of instruments at state expense. On a second tour of Europe in 1782, he met the astronomerPierre-Simon Laplace, the chemist Antoine-Laurent Lavoisier, and, most important, Franklin and Priestley. On his return, he introduced the American potato to Italian farmers. He continued his work on gases at Pavia, accurately measuring the thermal expansion of gases twenty years before Joseph-Louis Gay-Lussac.

During this time, Volta perfected his condensing electrometer, a more sensitive and less expensive form of the contemporaneous gold-leaf electrometer. In place of gold leaves, he suspended two fine straws in a square glass bottle, with a protractor scale on one face to give the degree of their divergence. The straws were suspended from a metal cover forming the base of a small electrophorus, with a thin slab of marble on top for the insulating cake. A movable upper plate had an increased capacity for storing charge because of the thinner cake, making it extremely sensitive to even minute charges. Lifting the upper plate increased the divergence of the electrometer straws. Following Henry Cavendish, Volta referred to this effect as increased tension resulting from decreased capacity and proposed a unit of tension (later called electric potential or voltage) in which a 1-degree spread of the straws corresponds to about 40 volts in modern measure. He also showed that electrical attraction on the upper plate follows the force law discovered by Charles-Augustin de Coulomb.

In 1792, Volta repeated Luigi Galvani’s experiments, published in Bologna in 1791, in which a metal attached to a frog’s crural nerve was brought in contact with a different metal attached to its leg muscle, causing it to contract. Characteristically, Volta tried to measure the effect and found a tension of only a fraction of a degree on his condensing electrometer. At first, he accepted Galvani’s idea that this was a unique form of animal electricity, but by the end of the year he concluded that the electricity was from the metals rather than the muscles. To illustrate the function of the metals, Volta joined a piece of tin on the tip of his tongue to a silver spoon touching farther back and experienced a sour taste. Early in 1793, he announced his conclusions in an open letter to Galvani’s nephew and defender, Giovanni Aldini, beginning a long debate. Volta’s position was strengthened by measurements of what he called the electromotive force of different combinations of conductors with his condensing electrometer, ranking them in what is now called the electrochemical series.

In 1794, Volta married Teresa Peregrina, and he quickly added three sons to his new family. In the same year, he became the first foreigner to win the Copley Medal from the Royal Society of London for his contributions to physics and chemistry. By 1796, he had shown the identity of galvanic and common electricity by stimulating his electrometer with only metals in contact. After trying various combinations of metals and moist conductors, he finally obtained a sustained galvanic current by placing a moist cardboard between two different metals. He increased this effect by stacking such pairs of silver and zinc disks to form an electric pile to multiply the flow of galvanic electricity. These results were made public in 1800 in a letter to Sir Joseph Banks, president of the Royal Society, and first published in its Philosophical Transactions in French under the English title “On the Electricity Excited by the Mere Contact of Conducting Substances of Different Kinds” (1800). The letter also described his “crown of cups,” consisting of a ring of cups filled with brine and connected by bimetallic arcs dipping into the liquid.

Volta might have published his work earlier had it not been for the distraction of the French invasion of Italy in 1796, which caused some damage to his laboratory and the closing of the university in 1799 for a year. In 1801, he demonstrated his work at the Paris Academy, where Napoleon I proposed that he be awarded a gold medal. Napoleon was so impressed with Volta’s discoveries that he gave him a pension and later made him a count and senator of the kingdom of Lombardy. He continued with a reduced schedule at the university until after the Austrians returned in 1814, and retired to Como in 1819, where he died after a long illness in 1827, on the same day as Laplace. During the last twenty years of his life, he enjoyed a large income from his pension and senatorial salaries but published only two minor scientific papers.

Significance

Alessandro Volta is a good example of a devoted scientist whose concentration and effort led to important discoveries and inventions. He was a deeply religious man who saw science and Christianity as allies, even seeking to defend religion from scientism with a confession of faith written in 1815. His many years of painstaking research in electrostatics and chemistry prepared him to capitalize on Galvani’s discovery of electricity in frogs. His prior inventions of the electrophorus and condensing electrometer helped him to explore the effects of galvanic electricity and demonstrate its equivalence with common electricity. His tireless efforts and hard-earned experience led to his crowning achievement in the invention of the voltaic pile.

Volta’s electric battery was one of the most important inventions of all time, providing the first useful form of electricity. The electrical revolution of the nineteenth century began with this one creation. In 1800, the year of its announcement, the English chemists William Nicholson and Anthony Carlisle used it to decompose water. Sir Humphry Davy built a powerful battery of five hundred plates at London’s Royal Institution and by 1808 had discovered potassium, sodium, calcium, magnesium, barium, strontium, and chlorine by electrolytic decomposition. Applications of discoveries that stem from Volta’s research have changed the world. Among the many honors paid to the founder of this revolution, perhaps the greatest was the international agreement in 1881 to name the unit of electromotive force the volt, recognizing the means of producing constant electric current that Volta gave to humankind.

Bibliography

Dibner, Bern. Alessandro Volta and the Electric Battery. New York: Franklin Watts, 1964. This biography of Volta includes historical background on the development of electricity, his early life and work, Galvani’s discovery and the resulting controversy, and the invention of the battery and its resulting influence. An appendix gives the English version of his letter to Banks, announcing his invention.

‗‗‗‗‗‗‗. Galvani-Volta: A Controversy That Led to the Discovery of Useful Electricity. Norwalk, Conn.: Burndy Library, 1952. This brief volume describes the work of Galvani, the defense of his ideas by Aldini, the work of Volta, the controversy that followed, and the results of Volta’s work. A supplement gives a facsimile of Volta’s letter to Banks in English translation as it appeared in The Philosophical Magazine in 1800.

Fara, Patricia. An Enlightenment for Angels: Electricity in the Enlightenment. Lanham, Md.: Totem Books, 2002. Provides brief explanations of experiments conducted by Volta, Galvani, Benjamin Franklin, and other seventeenth and eighteenth century scientists who studied electricity.

Heilbron, J. L. Electricity in the Seventeenth and Eighteenth Centuries: A Study of Early Modern Physics. Berkeley: University of California Press, 1979. This volume is an exhaustive study of the history of electricity up to the time of Volta. It includes a detailed analysis of his work in electrostatics but only a brief epilogue on the voltaic pile. Bibliography includes ten entries on the works of Volta.

Pancaldi, Giuliano. Volta: Science and Culture in the Age of Enlightenment. Princeton, N.J.: Princeton University Press, 2003. Focuses on the experiences in Volta’s life that transformed him from an amateur experimenter to an expert on electricity, including his experiments with torpedo fish that led him to invent the battery.

Pera, Marcello. The Ambiguous Frog: The Galvani-Volta Controversy on Animal Electricity. Translated by Jonathan Mandelbaum. Princeton, N.J.: Princeton University Press, 1992. Recounts how the two scientists offered different theories to explain why a dead frog’s muscles contracted when stimulated by electricity. Pera describes theories of electricity in the 1790’s, and compares the careers and laboratory procedures of Volta and Galvani.

Piccolino, Marco. The Taming of the Ray: Electric Fish Research in the Enlightenment from John Walsh to Alessandro Volta. Florence, Italy: Leo S. Olschki, 2003. Several scientists in the late eighteenth century conducted experiments that led them to discover the electrical properties of fish. The first of these experiments was believed to have been conducted by John Walsh, an Englishman, who studied torpedo fish from 1792 through 1795. Volta later conducted similar studies, which led him to invent the battery.

Potamian, Michael, and James Walsh. Makers of Electricity. Bronx, N.Y.: Fordham University Press, 1909. Chapter 5 in this volume, “Volta the Founder of Electrical Science,” gives a somewhat dated but interesting and readable account of Volta’s life and work.

Still, Alfred. Soul of Amber. New York: Murray Hill Books, 1944. Chapter 6 in this history of electrical science, titled “Electrical Science Becomes Methodical,” includes a description of Volta’s work on electrostatics. Chapter 8, “Electricity in Motion,” includes a discussion of the invention of the voltaic pile. Each chapter contains about thirty bibliographic references.