Voltaic Pile (1800): Alessandro Volta Invents the Battery

The voltaic pile, described by the Italian physicist Alessandro Volta in a letter dated 20 March 1800, was the first electric battery: a stack of metal discs and brine-soaked cardboard that produced a steady, continuous electric current. Before it, experimenters could only store static charge and release it in a single spark. Volta’s invention opened the way to electrochemistry, the discovery of new chemical elements and, within a generation, electromagnetism and the electric telegraph.

Background: electricity before 1800

Eighteenth-century scientists knew electricity mainly as static charge. Friction machines generated it, and Leyden jars stored it, but the charge escaped in an instant. There was no way to keep a current flowing through a wire long enough to study what it did.

The puzzle that led to the battery came from biology. In 1791 the Bologna anatomist Luigi Galvani published experiments in which dissected frog legs twitched when nerve and muscle were linked by an arc of two different metals. Galvani concluded that animals generate their own “animal electricity” (see Galvani and animal electricity).

Alessandro Volta and the contact theory

Alessandro Volta (1745–1827), born in Como in the Duchy of Milan, was already a celebrated experimenter. He had improved the electrophorus, a device for producing static charge, in 1775 and studied the flammable gas from marshes that we now call methane. From 1779 he was professor of experimental physics at the University of Pavia.

Volta at first accepted Galvani’s results but soon doubted his explanation. He noticed that the effect depended on the two metals being different. In the 1790s he argued that the contact of dissimilar metals itself generated electricity, and that the frog leg was simply a very sensitive detector. To prove the point he needed to produce the effect with no animal tissue at all.

Volta was well equipped for the task. He was a careful measurer who had built sensitive electrometers and a “condenser” that made tiny charges detectable. With these instruments he showed during the 1790s that two different metals in contact acquired small opposite charges. He arranged metals in a series according to the strength of the effect, with zinc at one end and silver and copper towards the other. The difficulty was that a single pair gave too weak a result to settle the argument with Galvani’s supporters, who continued to defend animal electricity.

How the pile worked

Volta’s solution was to multiply the effect of a single metal pair. He stacked discs in a repeating sequence: copper (or silver), zinc, then a disc of cardboard or cloth soaked in salt water, and so on, often 20 or more units high. Connecting the top and bottom of the column with a wire, or touching both ends with wet hands, gave a current that did not die away after a spark but kept flowing.

He also described a second form, the “crown of cups” (couronne de tasses): a ring of cups filled with brine or dilute acid, linked by bent strips of zinc and copper. Volta compared his column to the electric organ of the torpedo fish, which is likewise built from many repeated layers, and called it an artificial electric organ.

Today we know the energy comes from chemical reactions. Zinc dissolves in the electrolyte and gives up electrons, which flow through the outer wire to the copper side. Volta’s contact theory was therefore mistaken, but the device worked regardless.

Announcing the invention

Volta reported the pile in a long letter written in French to Sir Joseph Banks, President of the Royal Society in London, dated 20 March 1800. Banks showed the first part of the letter to colleagues before it was formally read. The full text was read to the Society on 26 June 1800 and published in its Philosophical Transactions that year.

Even before the reading, the London chemists William Nicholson and Anthony Carlisle built their own pile. In early May 1800 they passed its current through water and found that it split into hydrogen and oxygen gas. This was the first electrolysis, the use of electric current to drive a chemical reaction.

In November 1801 Volta demonstrated the pile at the Institut de France in Paris. Napoleon Bonaparte, then First Consul, attended and awarded him a gold medal. Volta later received further honours under Napoleonic rule, including the title of count in 1810.

Consequences: electrochemistry and new elements

The pile spread quickly through European laboratories, where scientists built ever larger batteries. At the Royal Institution in London, Humphry Davy used powerful piles to decompose substances that had resisted all chemical methods. In 1807 he isolated potassium and sodium by electrolysis of their molten compounds, and in 1808 he obtained calcium, barium, strontium and magnesium.

Davy also showed that the pile’s current arose from chemical change, which undermined Volta’s contact theory. With very large batteries he produced brilliant electric arcs between carbon rods, the ancestor of arc lighting.

Physicists, meanwhile, now had a steady current to study. In 1820 Hans Christian Ørsted used one to show that a current deflects a compass needle (Ørsted discovers electromagnetism). That discovery led to Michael Faraday’s work on electromagnetic induction in 1831 (Faraday and electromagnetic induction) and to the electric telegraph. Georg Ohm’s law of 1827, relating current, voltage and resistance, was worked out with batteries and thermocouples.

The original pile had flaws. Its output fell as bubbles of hydrogen collected on the copper plates, a problem called polarisation, and the brine-soaked discs dried out or leaked. John Frederic Daniell’s cell of 1836 solved polarisation and gave a much steadier current, which made batteries practical for the telegraph.

Key people

• Alessandro Volta (1745–1827): physicist at Pavia who designed the pile and championed the contact theory of electricity.
• Luigi Galvani (1737–1798): Bologna anatomist whose frog-leg experiments prompted Volta’s work.
• Sir Joseph Banks (1743–1820): President of the Royal Society, who received and presented Volta’s letter.
• William Nicholson and Anthony Carlisle: London scientists who first used the pile for electrolysis in 1800.
• Humphry Davy (1778–1829): chemist who used giant batteries to isolate new elements.

Myths and facts

Myth: Volta discovered electricity. Electricity had been studied for centuries. Volta’s achievement was the first source of continuous current.

Myth: the “Baghdad battery” shows that batteries existed in antiquity. Clay jars found near Baghdad, containing a copper cylinder and an iron rod, are sometimes claimed as ancient batteries. Most archaeologists see no evidence that they were used to produce electricity, and the voltaic pile remains the first documented battery.

Myth: Volta was right about how batteries work. His contact theory was largely abandoned in the nineteenth century in favour of the chemical explanation.

Legacy

The volt, the unit of electric potential difference, was named after Volta in 1881. His instruments are preserved in Italy, notably at the Tempio Voltiano, a museum in Como created to mark the centenary of his death in 1927. Every modern battery, from torch cells to the lithium-ion packs in phones and electric cars, follows his basic principle of linking electrochemical cells together to raise the voltage.

Timeline

• 1745, 18 February: Alessandro Volta is born in Como.
• 1775: Volta publicises his improved electrophorus.
• 1791: Luigi Galvani publishes his frog-leg experiments on animal electricity.
• 1800, 20 March: Volta describes the pile in a letter to Sir Joseph Banks.
• 1800, May: William Nicholson and Anthony Carlisle split water by electrolysis.
• 1800, 26 June: Volta’s letter is read to the Royal Society in London.
• 1801, November: Volta demonstrates the pile in Paris before Napoleon.
• 1807: Humphry Davy isolates potassium and sodium with large batteries.
• 1827, 5 March: Volta dies in Como.
• 1881: The volt is adopted as a unit in his honour.

Why it matters

The voltaic pile turned electricity from a fleeting spark into a steady current that could be measured, controlled and put to work. It founded electrochemistry, revealed new elements and made possible the discoveries that led to electric motors, generators and modern communications.