Definitions

# Alessandro Volta

[vohl-tuh or, It. vawl-tah for 1; vol-tuh, vohl- for 2]

Count Alessandro Giuseppe Antonio Anastasio Volta was a Lombard physicist known especially for the development of the first electric cell in 1800.

## Life

Volta was born in Como and educated in the public schools there. In 1775 he became professor of physics at the Royal School in Como; in the following year, he perfected the electrophorus, an instrument that produced charges of static electricity.

In 1776-77 he applied himself to chemistry, studying atmospheric electricity and devising experiments such as the ignition of gases by an electric spark in a closed vessel. In 1779 he became professor of physics at the University of Pavia, a chair he occupied for 25 years. By 1800 he had developed the so-called voltaic pile, a forerunner of the electric battery, which produced a steady stream of electricity.

In honor of his work in the field of electricity, Napoleon made him a count in 1810. A museum in Como, the Voltian Temple, has been erected in his honor and exhibits some of the original instruments he used to conduct experiments. Near Lake Como stands the Villa Olmo, which houses the Voltian Foundation, an organization which promotes scientific activities. Volta carried out his juvenile studies and made his first inventions in Como.

## Inventions and discoveries

In 1775, Volta improved and popularized the electrophorus, a device that produces a static electric charge. His promotion of it was so extensive that he is often credited with its invention, although it had actually been invented in 1764 by Swedish professor Johan Carl Wilcke In 1776-77 he studied the chemistry of gases, discovered methane, and devised experiments such as the ignition of gases by an electric spark in a closed vessel. Volta also studied what we now call capacitance, developing separate means to study both electrical potential V and charge Q, and discovering that for a given object they are proportional. This may be called Volta's Law of Capacitance, and likely for this work the unit of electrical potential has been named the volt. In 1779 he became professor of experimental physics at the University of Pavia, a chair he occupied for almost 40 years. In 1794, Volta married the daughter of Count Ludovico Peregrini, Teresa, with whom he raised three sons.

Around 1791 he began to study the "animal electricity" noted by Galvani when two different metals were connected in series with the frog's leg and to one another. He realized that the frog's leg served as both a conductor of electricity (we would now call it an electrolyte) and as a detector of electricity. He replaced the frog's leg by brine-soaked paper, and detected the flow of electricity by other means familiar to him from his previous studies of electricity. In this way he discovered the electrochemical series, and the law that the electromotive force (emf) of a galvanic cell, consisting of a pair of metal electrodes separated by electrolyte, is the difference of their two electrode potentials. That is, if the electrodes have emfs $mathcal\left\{E\right\}_\left\{1,2\right\}$, then the net emf is $mathcal\left\{E\right\}_\left\{2\right\}-mathcal\left\{E\right\}_\left\{1\right\}$. (Thus, two identical electrodes and a common electrolyte give zero net emf.) This may be called Volta's Law of the electrochemical series.

In 1800, as the result of a professional disagreement over the galvanic response advocated by Luigi Galvani, he invented the voltaic pile, an early electric battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and silver. Initially he experimented with individual cells in series, each cell being a wine goblet filled with brine into which the two dissimilar electrodes were dipped. The electric pile replaced the goblets with cardboard soaked in brine. (The number of cells, and thus the voltage it could produce, was limited by the pressure, exerted by the upper cells, that would squeeze all of the brine out of the cardboard of the bottom cell.)

In announcing his discovery of the pile, Volta paid tribute to the influences of William Nicholson, Tiberius Cavallo and Abraham Bennet.

## The Voltaic battery

The battery made by Volta is credited as the first electrochemical cell. It consists of two electrodes: one made of zinc, the other of copper. The electrolyte is sulfuric acid or a brine mixture of salt and water. The electrolyte exists in the form 2H+ and SO4 2-. The zinc, which is higher than both copper and hydrogen in the electrochemical series, reacts with the negatively charged sulphate. (SO4 ) The positively charged hydrogen bubbles start depositing around the copper and take away some of its electrons. This makes the zinc rod the negative electrode and the copper rod the positive electrode.

We now have 2 terminals, and the current will flow if we connect them. The reactions in this cell are as follows:

zinc
Zn --> Zn2+ + 2e-

sulfuric acid
2H+ + 2e- --> H2

The copper does not react, functioning as an electrode for the reaction.

However, this cell also has some disadvantages. It is unsafe to handle, as sulfuric acid, even if dilute, is dangerous. Also, the power of the cell diminishes over time because the hydrogen gas is not released, accumulating instead on the surface of the electrode and forming a barrier between the metal and the electrolyte solution.

## Honors

In honor of his work in the field of electricity, Napoleon made him a count in 1810; in 1815 the Emperor of Austria named him a professor of philosophy at Padua.

Before 1796, Lombardy was ruled by Austria. From 1796 to 1815, Lombardy came under Napoleon's rule. After 1815, Lombardy was once again under Austrian rule. Thus Volta was once a subject of the Emperor of Austria, later a subject of Napoleon and then later a subject of the Emperor of Austria again.

He was a long-time correspondent of the Royal Society and was made a fellow (FRS). He received the Society's 1794 Copley Medal. He published his invention of the Voltaic pile battery in 1800 in the Philosophical Transactions of the Royal Society. He was in correspondence with scientists in Austria, which ruled Lombardy in his day, and in France. His 1800 paper was written in French.

Volta is buried in the city of Como. At the Tempio Voltiano near Lake Como there is a museum devoted to explaining his work. Count Volta's original instruments and papers are on display there. The building, along with his portrait, appeared on Italian 10.000 lira banknote, before the introduction of the euro.

In 1881, an important electrical unit, the volt(V), was named in his honor. There have also been innovations and discoveries named after Alessandro Volta including the Toyota Alessandro Volta, and the Volta Crater on the Moon.

## Retirement

Volta entered retirement in Spain.

Children

1. Christian Volta [1765-1839]
2. Alezandro Volta [1767-1844]
3. Louis Volta [1768-1845]
4. Johann Volta [1771-1850]
5. Magdalena Volta [1773-1854]
6. Alessandro Volta Junior [1776-1855]