Professor Allessandro Volta

An Italian physicist known especially for the invention of the battery in 1800, he was born in Como, Italy, and taught in the public schools there. In 1774, he became a physics professor at the Royal School in Como. A year later, he 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, even though a machine operating in the same principle was described in 1762 by Swedish professor Johan Wilcke. In 1776-77 he studied the chemistry of gases. He discovered methane by collecting the gas from marshes. He devised experiments such as the ignition of methane by an electric spark in a closed vessel. He also studied what we now call electrical 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 25 years. In 1794, he married an aristocratic lady also from Como, Teresa Peregrini, with whom he raised three sons, Giovanni, Flaminio and Zanino. He realized that in the "animal electricity" noted by Luigi Galvani when two different metals were connected in series with the frog's leg and to one another, 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 with brine-soaked paper, and detected the flow of electricity by other means familiar to him from his previous studies. 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 between their two electrode potentials (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 Galvani, he invented the voltaic pile, an early electric battery, which produced a steady electric current. He 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 voltaic pile replaced the goblets with cardboard soaked in brine. In announcing his discovery of the pile, he paid tribute to the influences of William Nicholson, Tiberius Cavallo and Abraham Bennet. An additional invention he pioneered was the remotely operated pistol. He made use of a Leyden jar to send an electric current from Como to Milan (~50 km or ~30 miles), which in turn, set off the pistol. The current was sent along a wire that was insulated from the ground by wooden boards. This invention was a significant forerunner of the idea of the telegraph which also makes use of a current to communicate. The battery he made 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 SO42-. The zinc, which is higher than both copper and hydrogen in the electrochemical series, reacts with the negatively charged sulfate (SO42-). The positively charged hydrogen ions (protons) capture electrons from the copper, forming bubbles of hydrogen gas, H2. This makes the zinc rod the negative electrode and the copper rod the positive electrode. 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 zinc electrode and forming a barrier between the metal and the electrolyte solution. In honor of his work, he was made a count by Napoleon in 1801. Furthermore, he was depicted upon the Italian 10,000 Lire (no longer in circulation) along with a sketch of his famous Voltaic Pile. He retired in 1819 in his estate in Camnago, a frazione of Como now called Camnago Volta after him, where he died on March 5, 1827. He is buried in Camnago Volta. His legacy is celebrated by a Temple located in the public gardens by the lake. It is also a museum which has been built in his honor and exhibits some of the original equipment he used to conduct experiments; not far away stands the Villa Olmo, which houses the Voltian Foundation, an organization promoting scientific activities. He carried out his experimental studies and made his first inventions in Como. He published a work called, ?De vi attractiva ignis electrici? (1769) (On the attractive force of electric fire)