Luigi Galvani - bioelectricity researcher

Born on September 9, 1737 in Bologna (Papal States), he lived and died there on December 4, 1798, having lived a full 61 years. By occupation he was a doctor, physicist and philosopher, which was quite common at that time. His Latin name reads Aloysius Galvani.

Luigi Galvani was the first to explore bioelectricity. In 1780, Luigi conducted experiments on the bodies of dead frogs. He passed an electric current through their muscles, and their paws twitched, the muscles began to contract. This was the first step towards studying the signals of the nervous system.

Brief biography

Luigi Galvani (1737-1798)

Born to Dominico and his fourth wife, Barbara Foschi. Luigi's parents were not aristocrats, but they had enough money to educate one of their children. Luigi Galvani wanted to receive a church religious education, in that era it was largely prestigious, and he studied for 15 years at a religious institute, namely at the Padri Filippini chapel (Oratorio dei Padri Filippini). In the future, he planned to take religious vows, but his parents convinced him not to do this and to continue his education further. Around 1755, Luigi entered the Faculty of Arts at the University of Bologna. There, Luigi took a medical course in which he studied the works Hippocrates, Galena And Avicenna (Ibn Sina). In addition to studying works, Luigi was engaged in medical practice, including surgery. This allowed him to further study and research bioelectricity.

In 1759, Luigi Galvani received a degree in medicine and philosophy, which entitled him to lecture at the university after defending his thesis, which he defended on June 21, 1761. Already in 1762 he became an honorary lecturer in anatomy and surgery. In the same year, he married Lucia Galeazzi, the daughter of one of the university professors. Luigi moved to live in the house of Professor Galeazzi and helped him in his research. After the death of his father-in-law in 1775, Luigi Galvani was appointed teacher in place of the deceased Galezzi.

Galvani's responsibility as a member of the Academy of Sciences from 1776 included regular research in the field of practical human anatomy. He was required to publish at least one study per year.

Experiments with frogs

After several years, Luigi Galvani began to show interest in the medical uses of electricity. This area of ​​research has emerged since the mid-18th century, after the effects of electricity on the human body were discovered.

Diagram of Luigi Galvani's experiment with a frog body, circa late 1780s

There is a legend according to which the beginning of experiments with bioelectricity was based on an incident that occurred as follows.

Luigi placed a dead frog on a table to experiment with its skin to generate static electricity. Previously, experiments with static electricity had already been carried out on the table, and it turned out that his assistant (assistant) touched a metal scalpel with an electric charge to the exposed sciatic nerve of the frog. He must have been planning to dissect it. But then something unexpected happened. The assistant saw sparks and the leg of the dead frog contracted as if it were alive.

This observation was the first step towards starting research bioelectricity. A connection was discovered between nervous activity and electricity, between biological life and electrical signals. It became obvious that muscle activity is carried out with the help of electricity, with the help of current in electrolytes. Before this, it was generally accepted in science that muscle activity occurs through a certain substance called after the elements of air and water.

Galvani introduced the term - animal electricity(animal electricity) to describe the force that activates muscles. This phenomenon was later called galvanism (galvanism), but after Galvani at the suggestion of his contemporaries.

At the moment, the study of the galvanic effects of biology is carried out by such a branch as electrophysiology. Name galvanism used more in a historical context than in a scientific one.

Galvani vs Volta

Professor of Experimental Physics Alessandro Volta at the University of Pavia (Pavia) was the first scientist who doubted the correctness of Galvani's experiments and continued his research.

His goal was to determine whether the cause of muscle contraction is actually bioelectricity, or it occurs as a result of metal contact. It was understood that living cells cannot generate electricity, which means then there is no animal electricity.

Alessandro Volta tested my hypothesis and found out that, indeed, living cells are capable of generating electricity, which means bioelectricity exists, living cells are sources of current. Volta's hypothesis that muscles contract only as a result of external electricity, when they touch a metal object with a static charge, was refuted by him. Further research Alessandro Volta led him to the creation of a galvanic battery, which uses electrochemical phenomena similar to those that occur in living cells.

As a result of research, Volta discovered that each cell has its own cellular potential, which bioelectricity has the same chemical bases as electrochemical cells that produce a potential difference. Alessandro Volta showed respect to his colleague and introduced the term galvanism to highlight the merit of Luigi Galvani in the discovery bioelectricity. However, Volta objected to some special electricity in the form animal electrical fluid, and he was right. The reward was the creation of chemical current sources - galvanic cells. Alessandro Volta the first to build chemical batteries consisting of many galvanic cells. Such batteries were called volt pole, a source with an EMF value of more than 100 Volts was assembled from many elements, which made it possible to further study the phenomena of electricity.

Works of Luigi Galvani

Luigi Galvani's major work bioelectricity called De Viribus Electricitatis in Motu Musculari Commentarius (PDF format), translated into Russian Treatise on the forces of electricity during muscular movement (djvu format). You can download these works for in-depth study and expanding your horizons.

Until the end of the 18th century, physicists studying electrical phenomena had at their disposal only sources of static electricity - pieces of amber, balls of fused sulfur, electrophore machines, Leyden jars. Many scientists experimented with them, starting with the English physicist and physician William Gilbert (1544–1603). Having such sources at our disposal, it was possible to discover, for example, Coulomb's law (1785), but it was impossible to discover even Ohm's law (1826), not to mention Faraday's laws (1833). Because the accumulated static charge was small and could not provide a current lasting at least a few seconds.

The situation changed after the work of the professor of medicine at the University of Bologna, Luigi Galvani (1737–1798), who discovered, as he believed, “animal electricity.” His famous treatise was called “On the Forces of Electricity in Muscular Movement.” In some of Galvani's experiments, the world's first reception of radio waves occurred. The generator was sparks from an electrophore machine, the receiving antenna was a scalpel in Galvani's hands, and the receiver was a frog's leg. Galvani's assistant conducted experiments with an electric machine at some distance from the dissected frog. At the same time, Galvani's wife Lucia noticed that the frog's legs contract at the very moment when a spark jumps in the machine, so that the role of both chance and observation is visible.

The Italian physicist Alessandro Giuseppe Antonio Anastasio Volta (1745–1827) became interested in Galvani's experiments. He was already a famous scientist: in 1775 he designed a resin electrophore, that is, he discovered electret substances, in 1781 - a sensitive electroscope, and a little later - a capacitor, an electrometer and other instruments. In 1776, he also discovered the electrical conductivity of flame, and in 1778, for the first time, he obtained pure methane from gas he collected in swamps and demonstrated the ability to ignite it from an electric spark. Volta was at first an ardent supporter of Galvani's theory of “animal electricity”. But his own repetition of his experiments convinced Volta that Galvani’s experiments should be explained in a completely different way: the frog’s leg is not a source, but only a receiver of electricity. The source is different metals that touch each other. “Metals are not only excellent conductors,” wrote Volta, “but also engines of electricity.”

This was the key statement that made it possible to create galvanic cells, batteries, and accumulators that surround us on all sides and throughout our lives. The principle of their operation is described in the school textbook, and in much more detail than is necessary for further discussion. The essence is simple: in a conducting medium (electrolyte) there are two different conductors (electrodes), which react with it in such a way that they are charged with opposite charges. If you connect these electrodes (anode and cathode) with an external conductor (load), current will begin to flow through it.

Objecting to Galvani, Volta first got rid of the frog, replacing it own language. For example, he placed a gold or silver coin on his tongue, and a copper coin under his tongue. As soon as two coins were connected with a piece of wire, a sour taste was immediately felt in the mouth, familiar to anyone who has tasted the contacts of a flashlight battery on the tongue. Then Volta completely excluded “animal electricity” from the experiments, using only instruments in his experiments.

There was one step left until the invention in 1800 of the first permanent source of electric current. This happened when Volta connected pairs of zinc and copper plates in series, separated by spacers of cardboard or leather, which were soaked in an alkali solution or salt water. This design was called the “voltaic pillar” after the inventor. The design was heavy, the liquid was squeezed out of the gaskets, so Volta replaced it with cups with an acid solution, into which zinc and copper (or silver) strips or circles were dipped. The cups were connected in series, and to keep the battery terminals close, Volta placed its individual elements in a circle. This design was called the “Voltic crown” due to its shape.

After his discovery, Volta lost interest in him and moved away from scientific work, leaving other scientists to develop the doctrine of electricity. But Alessandro Volta’s contribution to the study of electricity is so significant that the unit of voltage is named after him. And when Napoleon saw in the library of the Academy of Sciences an image of a laurel wreath with the inscription “To the Great Voltaire,” he erased several letters, so it turned out: “To the Great Volta.” The voltaic column and its variations have enabled numerous scientists to conduct experiments with a long-lasting direct current source. It was with this discovery that the era of electricity began. Probably the most enthusiastic review of Volta’s discovery was left by his biographer, the French physicist Dominique François Arago (1786–1853): “A column composed of circles of copper, zinc and wet cloth. What to expect a priori from such a combination? But this collection, strange and apparently inactive, this column of dissimilar metals separated by a small amount of liquid, constitutes a projectile more wonderful than which man has never invented, not even excluding the telescope and the steam engine.”

“Huge batteries”

Volta wisely sent a letter in March 1800 to Joseph Banks (1743–1820), President of the Royal Society of London - leading scientific center of that time. In the letter, Volta described the various designs of his sources of electricity, which he called galvanic in memory of Galvani. Banks was a botanist, so he showed the letter to his colleagues - the physicist and chemist William Nicholson (1753–1815) and the physician and chemist, President of the Royal College of Surgeons Anthony Carlyle (1768–1842). And already in April, according to Volta’s description, they made a battery from 17, and then from 36 series-connected zinc circles and half-crown coins, which were then made of 925 silver. Between them were placed cardboard pads soaked in salt water.

During the experiments, Nicholson discovered the release of gas bubbles near the contact of zinc and copper conductor. He determined that it was hydrogen - and by its smell, because hydrogen obtained by dissolving zinc in acids or alkalis often has an odor. Zinc usually contains an admixture of arsenic, which is reduced to arsine, and its decomposition products smell like garlic. In September 1800, the German physicist Johann Ritter (1776–1810) collected the gas released during the electrolysis of water from another battery electrode and showed that it was oxygen. In the same year, the English chemist William Cruikshank (1745–1800) placed zinc and copper plates in a horizontal long box - while it was easy to replace spent (half-dissolved and covered with reaction products) zinc electrodes. When not in use, the electrolyte was drained from the box so as not to waste zinc. Cruickshank used ammonium chloride solution as an electrolyte, and then dilute acid. Faraday recommended a mixture of weak (1–2%) solutions of sulfuric and nitric acids. With this electrolyte, the zinc slowly dissolved, releasing small bubbles of hydrogen. Hydrogen was also released on the copper anode, and the emf of one battery cell was only 0.5 V.

The evolution of hydrogen on zinc is associated with the polarization of this electrode, which increases the internal resistance and lowers the potential of the element. To prevent this phenomenon, British physicist and electrical engineer William Sturgeon (1783–1850), creator of the first electromagnet, amalgamated zinc plates. In 1840, the English physician Alfred Smee (1818–1877) replaced the copper electrode with a silver electrode coated with a rough layer of platinum. This accelerated the release of hydrogen bubbles from the solution and increased the emf. Such batteries were widely used in electroplating technology. Thus, sculptures were made at St. Isaac's Cathedral in St. Petersburg using the electroplating method. The method of producing electrolytic copies in metal was developed by the St. Petersburg academician Moritz Hermann (Boris Semenovich) Jacobi in 1838, just during the construction of the cathedral. You can read more about this technique on the website “Library with books on sculpture”.

One of the best batteries of his time was assembled by the famous English physician and chemist William Hyde Wollaston (Wollaston, 1766–1828), famous for the discovery of palladium and rhodium, as well as the technology for manufacturing the finest metal threads that were used in sensitive instruments. In each cell, a zinc electrode was surrounded on three sides by a copper electrode with a small gap through which hydrogen bubbles were released into the air.

The famous English physicist Humphry Davy (1778–1829) first conducted experiments with a battery given to him by Volta himself; then he began to produce increasingly powerful ones of his own design - from copper and zinc plates separated by an aqueous solution of ammonia. His first battery consisted of 60 such elements, but a few years later he assembled a very large battery, already consisting of a thousand elements. With the help of these batteries, he was for the first time able to obtain metals such as lithium, sodium, potassium, calcium and barium, and in the form of amalgam - magnesium and strontium.

One of the largest batteries was created in 1802 by the physicist and electrical engineer Vasily Vladimirovich Petrov (1761–1834). His “huge battery” of 4,200 copper and zinc plates “one and a half inches” in size was located in narrow wooden boxes. The entire battery was composed of four rows, each about 3 m long, connected in series with copper brackets. Theoretically, such a battery can produce a voltage of up to 2500 V, but in reality it gave about 1700. This giant battery allowed Petrov to conduct many experiments: he decomposed with current various substances, and in 1803 he received an electric arc for the first time in the world. With its help, it was possible to melt metals and brightly illuminate large rooms. However, maintaining this battery was extremely labor intensive. During the experiments, the plates oxidized and had to be cleaned regularly. Moreover, one worker could clean 40 plates in an hour. Working 8 hours a day, this worker alone would have spent at least two weeks preparing the battery for the next experiments.

Probably the most unusual voltaic cell was made by the German chemist Friedrich Wöhler (1800–1882). In 1827, by heating aluminum chloride with potassium, he obtained metallic aluminum - in powder form. It took him 18 years to obtain aluminum in the form of an ingot. In the Wöhler element, both electrodes were made of aluminum! Moreover, one was immersed in nitric acid, the other - into a solution of sodium hydroxide. The vessels with solutions were connected by a salt bridge.

Daniel, Leclanche and others

The basis of modern galvanic cells was developed in 1836 by John Frederick Daniel (1790–1845), an English physicist, chemist and meteorologist (he also invented a humidity meter - a hygrometer). Daniel managed to overcome the polarization of the electrodes. In his first element, a piece of a bull's esophagus filled with dilute sulfuric acid with a zinc rod in the middle was inserted into a copper vessel containing a solution of copper sulfate. Faraday proposed isolating the zinc with wrapping paper, the pores of which could also allow electrolyte ions to pass through. But Daniel began using a porous clay vessel as a diaphragm. Note that back in 1829, Antoine César Becquerel (1788–1878), grandfather of the more famous Antoine Henri Becquerel, who discovered radioactivity and shared it with the Curies in 1903, experimented with copper and zinc electrodes immersed in solutions of copper nitrate and zinc sulfate, respectively, back in 1829. Nobel Prize in Physics. Daniel's element produced a stable voltage of 1.1 V for a long time. For this invention, Daniel was awarded the highest award of the Royal Society - the Copley Gold Medal. Over the past 180 years, many modifications of this element have appeared; at the same time, their developers tried different ways to get rid of the porous vessel.

With the advent of telegraph lines, a need arose for more convenient and inexpensive current sources, without porous partitions, with a single electrolyte and with a long service life. In 1872, the Daniel element was replaced by the normal element of Josiah Latimer Clark (1822–1898): positive electrode - mercury, negative - 10% zinc amalgam, emf 1.43 V. And in 1892 it was replaced by Edward's mercury-cadmium element Weston (1850–1936) with an emf of 1.35 V. Its modification, called the normal Weston element, is still used as a voltage standard - at low loads it gives a highly stable voltage in the range of 1.01850–1.01870 V, known with accuracy up to the fifth character.

One version of the Daniel element, which did not have a porous septum, was developed in 1859 by the German physicist and inventor Heinrich Meidinger (1831–1905). At the bottom of the vessel there is a copper electrode and crystals of copper sulfate (they come from the funnel), the zinc electrode is fixed at the top. A heavy saturated solution of copper sulfate remains in the lower part: the diffusion of copper ions to the zinc electrode is counteracted by the discharge of these ions during operation of the element, and the boundary between the solutions stands out very sharply. Hence the name of sources of this type - gravitational element. The Meidinger element can operate continuously for several months without maintenance or addition of reagents. This element was widely used in Germany from 1859 to 1916 as a power source for the railway telegraph network. Similar sources existed in France and the USA - under the name of Callot and Lockwood elements. The element proposed in 1839 by the English physicist and chemist William Robert Grove (1811–1896) had good characteristics. The electrodes in it were zinc and platinum, separated by a porous partition and immersed, respectively, in solutions of sulfuric and nitric acids.

Robert Wilhelm Bunsen (1811–1899), known for his discoveries and inventions (spectral analysis, burner, etc.), replaced the expensive platinum electrode with pressed carbon. Carbon electrodes are also present in modern batteries, but in Bunsen they were immersed in nitric acid, which plays the role of a depolarizer (now they are manganese dioxide). Bunsen's elements have been widely used in laboratories for a long time. They could provide, albeit for a short time, a large current. Bunsen elements, for example, were used by the young Charles Martin Hall (1863–1914), who discovered the electrolytic method for producing aluminum. Many such cells were connected to form a battery; At the same time, almost 16 g of zinc were required for 1 g of isolated aluminum! The French chemist and inventor Edme Hippolyte Marie-Davy (1820–1893) replaced nitric acid in the Bunsen element with a paste of mercury(I) sulfate and sulfuric acid; The electrolyte was a solution of zinc sulfate. In 1859, a comparison was made of a battery of 38 of these cells (emf of each 1.4 V) with a battery of 60 Daniel cells. The first worked for 23 weeks, the second - only 11. However, the high cost and toxicity of mercury salts prevented the widespread use of such elements.

The German physicist Johann Christian Poggendorff (1796–1877) used a solution of potassium dichromate in sulfuric acid as a depolarizer in his element. Poggendorff is known as the publisher of the magazine Annalen der Physik und Chemie- He held this post for 36 years. The Poggendorff element produced the highest EMF (2.1 V) and for a short time - high current. An important advantage was the ability to remove the zinc electrode from the solution in order to clean or replace it.

Warren de la Rue (1815–1889), who first took photographs of the Moon and the Sun, assembled a large battery of 14 thousand cells in 1868. The electrodes in them were silver coated with silver chloride and amalgamated zinc, and the electrolyte was a solution of sodium chloride, zinc chloride or potassium hydroxide. Zinc-silver chloride cells are still used today; they are stored dry and activated by filling with fresh or sea water, after which the element can operate for up to 10 months. Such elements can be used by victims of a water accident. Cheaper but less powerful cells use a Cu/CuCl electrode.

One of the most famous chemical current sources is the manganese-zinc element, described in 1868 by the French chemist Georges Leclanche (1839–1882) and developed by him several years earlier. In this cell, the carbon electrode is surrounded by a depolarizer of manganese dioxide, mixed with carbon powder for better electrical conductivity. To prevent the mixture from crumbling when pouring the electrolyte (ammonium chloride solution), it was placed together with the anode in a porous vessel. The Leclanche element served for a long time, did not require maintenance and could produce quite a large current. Trying to make it more convenient, Leclanche decided to thicken the electrolyte with a paste. This changed things in a revolutionary way: Leclanchet’s elements were no longer afraid of accidentally tipping over, they could be used in any position. Leclanche's invention immediately received commercial success, and the inventor himself, abandoning his main profession, opened a factory for the production of elements. Leclanchet's manganese-zinc cells were cheap and produced in large quantities. However, calling them “dry” is not entirely correct: the electrolyte in them was “semi-liquid”, but in real dry cells it should be solid. Leclanche died at the age of 43, before the invention of such elements.

From 1802 to 1812, several dry batteries were constructed, the most famous of which is the so-called zamboniev, or zamboniev pillar (see “Chemistry and Life” No. 6, 2007). The Italian physicist and priest Giuseppe Zamboni (1776–1846) in 1812 assembled a column of several hundred paper circles, on one side of which there was a thin layer of zinc, and on the other a mixture of manganese dioxide and vegetable gum. The electrolyte was the moisture contained in the paper. Such a pole produced a high voltage, but only a very small current. It is the Zamboni pillar that has allowed the cups to jingle in the bell, located in the Clarendon Laboratory in Oxford, for almost two centuries. However, such a battery is not suitable for practical purposes.

The first dry galvanic cell that could be used in practice was patented in 1886 by the German engineer Karl Gassner (1855–1942). Flowing in it chemical reactions were the same as in the previous designs: Zn + 2MnO 2 + 2NH 4 Cl → 2MnO(OH) + Cl 2. In this case, the zinc electrode simultaneously served as an outer container. The electrolyte was a mixture of flour and gypsum; a solution of ammonium and zinc chlorides was absorbed on it (gypsum was later replaced with starch). The addition of zinc chloride to the electrolyte significantly reduced the corrosion of the zinc electrode and extended the shelf life of the cell. The positive electrode was a carbon rod, which was surrounded by a mass of manganese dioxide and soot in a paper bag. The element was sealed on top with bitumen. The capacity of the elements was compensated by their size. Gassner's salt element general outline has survived to this day and is produced in quantities of many billions per year. But in the twentieth century, they were competed by alkaline elements, which are sometimes mistakenly called “alkaline”, without bothering to look in the dictionary when translating from English.

In conclusion, we note that galvanic batteries of one design or another were the main sources of electricity until the invention of the dynamo.

Electromotive force. - "Elements".

Doctor of Physical and Mathematical Sciences V. OLSHANSKY

MYSTERIOUS TRIUMPH

Volta demonstrates his invention to Napoleon - the Voltaic Pillar.

Luigi Galvani (1737-1798).

Lucia Galeazzi, Galvani's wife.

In his experiments, Galvani used an electrophore machine similar to this one.

Galvani, his wife and an assistant conduct an experiment in their home laboratory. A. Muzzi, 1862.

A frog prepared for experiments with an electrophore machine and a Leyden jar. Drawing from Galvani's treatise.

Scheme of an experiment to study atmospheric electricity. The detector is a frog's leg, the nerve of which is connected to a lightning rod, and the muscle is connected through a conductor to water in the well. Drawing from Galvani's treatise.

Alessandro Volta (1745-1827).

A voltaic column consisting of metal disks separated by circles of wet cloth.

In 1801, a striking event took place in Paris, repeatedly described by historians of science: in the presence of Napoleon Bonaparte, a presentation of the work “An artificial electric organ imitating the natural electric organ of an eel or stingray” was presented with a demonstration of a model of this organ. Napoleon generously rewarded the author: a medal was struck in honor of the scientist and a prize of 80,000 ecus was established. All presenters scientific societies of that time, including the St. Petersburg Academy of Sciences, expressed a desire to see him in their ranks, and best universities Europe was ready to provide him with their chairs. He later received the title of count and was appointed a member of the Senate of the Kingdom of Italy. The name of this man is well known today, and various versions of artificial electrical organs that imitate natural ones are produced in billions of quantities. We are talking about Alessandro Volta and his invention - the Voltaic Column, the prototype of all modern batteries and accumulators. What does the Voltaic column have to do with the electrical organs of fish - more on this later, but for now let us pay attention to the fact that the demonstration was carried out with emphatic pomp and in front of a large crowd of people.

The voltaic column supposedly produced a voltage of 40-50 volts and a current of less than one ampere. What exactly did Volta have to show to capture everyone's imagination? Imagine that it’s not Volta, but you, standing in front of Napoleon with a box full of the best batteries and wanting to demonstrate something spectacular with them. Light bulbs, motors, players, etc. are not even an idea yet. Roughly speaking, where could Volta put his batteries?

The electrophoric machine had long been known by that time; the Leyden jar had been invented more than 50 years earlier. Everything associated with sparks, crackling, glowing electrified balls, and the simultaneous jumping of a large group of people from an electric shock has been demonstrated more than once and has not caused even a small fraction of such honors and awards. Why did the triumph fall to the share of the Voltaic Pillar?

Apparently, the secret of success was that Volta repeated before Napoleon the experiments of reviving severed members with the help of small amounts of electricity. “I did them not only on frogs, but also on eels and other fish, on lizards, salamanders, snakes and, more importantly, on small warm-blooded animals, namely mice and birds,” the scientist wrote in 1792, in the very the beginning of research that ultimately led to a great invention. Imagine various severed parts of various animals lying completely motionless, as befits severed limbs from which the life force has flowed. The slightest touch of the Voltaic column - and the flesh comes to life, trembles, contracts and shudders. Have there been more amazing experiments in the history of science?

But everyone knows that the idea of ​​these experiments did not belong to Volta, but to Luigi Galvani. Why wasn't he honored first, or at least next to Volta? The reason is not that Galvani had already died by that time - if he had lived, the Napoleonic award would most likely have gone to Volta. And it’s not about Napoleon - in subsequent years he was not the only one who elevated Volta and belittled Galvani. And there were reasons for that.

STUBBORN "FROG POOL"

From physics textbooks, approximately the following is known about Luigi (or, in Latinized form, Aloysius) Galvani: Italian physician, anatomist and physiologist of the late 18th century; He stumbled upon the phenomenon, called the “Galvani experiment,” by accident and could not correctly explain it, since he proceeded from a false hypothesis about the existence of some kind of animal electricity. But physicist Alessandro Volta was able to understand the phenomenon and create a useful device based on it.

It would seem that the picture is clear: the anatomist was cutting up frogs (what else can an anatomist do?), accidentally stumbled upon the fact that the leg twitches under the influence of current, and did not understand anything - he is not a physicist, how can he understand the essence of things. Volta, a physicist, carefully repeated everything, explained everything correctly and even confirmed it with practice. And the fact that the anatomist and doctor, either out of stubbornness or thoughtlessness, continued to insist on his own, completely characterizes him poorly.

It is not clear why humanity turned out to be so supportive of this doctor that it assigned his name to conduction currents, and an entire field of physics, and a device for measuring current, and the most important technological process of electrochemical deposition of metal coatings, and even the current sources invented by Volta. Not one of the most famous physicists - neither Newton, nor Descartes, nor Leibniz, nor Huygens, nor the darling of classical physics, James Clerk Maxwell - is associated with so many terms.

But here's the funny thing: when it comes to non-physical fields, the terms associated with the name Galvani are quite respectable and stable: galvanotherapy, galvanic bath, galvanotaxis. If it concerns physics, then for every galvanic term there is an antigalvanic term: not a galvanometer, but an ammeter; not galvanic current, but conduction current; not a galvanic cell, but a chemical current source. The more orthodox a physics textbook, the less likely it is to find in it not only any mention of Galvani’s scientific merits, but also galvanic terminology. The official authorities of Sir Isaac Newton's empire, or "guild men" as Goethe called them, clearly deny citizenship to Luigi Galvani, but someone constantly writes his name on the walls of the temple of science and reminds of his existence.

And now we will talk about research conducted almost two hundred years after the publication of Gilbert’s work. They are associated with the names of the Italian professor of anatomy and medicine Luigi Galvani and the Italian professor of physics Alessandro Volta.

In the anatomy laboratory of the University of Boulogne, Luigi Galvani conducted an experiment, the description of which shocked scientists all over the world. Frogs were dissected on a laboratory table. The objective of the experiment was to demonstrate and observe the naked nerves of their limbs. On this table there was an electrostatic machine, with the help of which a spark was created and studied. Let us quote the statements of Luigi Galvani himself from his work “On Electrical Forces during Muscular Movements”: “... One of my assistants accidentally very lightly touched the internal femoral nerves of the frog with a point. The frog’s leg jerked sharply.” And further: “... This is possible when a spark is extracted from the machine’s capacitor.”

This phenomenon can be explained as follows. The atoms and molecules of air in the area where the spark occurs are subject to a changing electric field; as a result, they acquire an electric charge and cease to be neutral. The resulting ions and electrically charged molecules spread over a certain, relatively short distance from the electrostatic machine, since when moving, colliding with air molecules, they lose their charge. At the same time, they can accumulate on metal objects that are well insulated from the surface of the earth, and are discharged if a conductive electrical circuit to the ground occurs. The floor in the laboratory was dry, wooden. He well insulated the room where Galvani worked from the ground. The object on which the charges accumulated was a metal scalpel. Even a slight touch of the scalpel to the nerve of the frog led to a “discharge” of static electricity accumulated on the scalpel, causing the leg to be withdrawn without any mechanical destruction. The phenomenon of secondary discharge itself, caused by electrostatic induction, was already known at that time.

The brilliant talent of an experimenter and the conduct of a large number of diverse studies allowed Galvani to discover another phenomenon important for the further development of electrical engineering. Experiments are underway to study atmospheric electricity. Let's quote Galvani himself: "... Tired... of futile waiting... began... to press the copper hooks stuck into the spinal cord against the iron grate - the frog's legs shrank." The results of the experiment, conducted not outdoors, but indoors in the absence of any working electrostatic machines, confirmed that a contraction of the frog muscle, similar to the contraction caused by the spark of an electrostatic machine, occurs when the frog's body is touched simultaneously by two different metal objects - a wire and a plate of copper, silver or iron. No one had observed such a phenomenon before Galvani. Based on the results of observations, he makes a bold, unambiguous conclusion. There is another source of electricity, it is “animal” electricity (the term is equivalent to the term “electrical activity of living tissue”). Living muscle, Galvani argued, is a capacitor like a Leyden jar, positive electricity accumulates inside it. The frog's nerve serves as an internal "conductor". Connecting two metal conductors to a muscle causes an electric current to occur, which, like a spark from an electrostatic machine, causes the muscle to contract.

Galvani experimented in order to obtain an unambiguous result only on frog muscles. Perhaps this is what allowed him to propose using a “physiological preparation” of a frog’s leg as a meter for the amount of electricity. A measure of the amount of electricity, for the assessment of which a similar physiological indicator served, was the activity of raising and falling the paw when it comes into contact with a metal plate, which is simultaneously touched by a hook passing through the spinal cord of the frog, and the frequency of raising the paw per unit time. For some time, such a physiological indicator was used even by prominent physicists, and in particular Georg Ohm.

Galvani's electrophysiological experiment allowed Alessandro Volta to create the first electrochemical source of electrical energy, which, in turn, opened a new era in the development of electrical engineering.

Alessandro Volta was one of the first to appreciate Galvani's discovery. He repeats Galvani's experiments with great care and receives a lot of data confirming his results. But already in his first articles “On Animal Electricity” and in a letter to Dr. Boronio dated April 3, 1792, Volta, unlike Galvani, who interprets the observed phenomena from the standpoint of “animal” electricity, highlights chemical and physical phenomena. Volta establishes the importance of using dissimilar metals (zinc, copper, lead, silver, iron) for these experiments, between which a cloth soaked in acid is placed.

Here is what Volta writes: “In Galvani’s experiments, the source of electricity is a frog. However, what is a frog or any animal in general? First of all, these are nerves and muscles, and in them various chemical compounds. If the nerves and muscles of a dissected frog are connected to two dissimilar metals, then when such a circuit is closed, an electrical effect is manifested. My last experiment also involved two dissimilar metals - staniol (lead) and silver, and the role of the liquid was played by the saliva of the tongue. By closing the circuit with a connecting plate, I created conditions for the continuous movement of electrical fluid from one place to another. But could I simply put these same metal objects in water or in a liquid like saliva? What does “animal” electricity have to do with it?”

Experiments conducted by Volta allow us to formulate the conclusion that the source of electrical action is a chain of dissimilar metals when they come into contact with a damp cloth or a cloth soaked in an acid solution.

In one of the letters to his friend, the doctor Vasaghi (again an example of the doctor’s interest in electricity), Volta wrote: “I have long been convinced that all the action comes from metals, from the contact of which the electric fluid enters a moist or watery body. On this basis, I believe himself has the right to attribute all new electrical phenomena to metals and replace the name “animal electricity” with the expression “metallic electricity”.

According to Volta, a frog's legs are a sensitive electroscope. A historical dispute arose between Galvani and Volta, as well as between their followers - a dispute about “animal” or “metallic” electricity.

Galvani did not give up. He completely excluded metal from the experiment and even dissected frogs with glass knives. It turned out that even with such an experiment, the contact of the frog's femoral nerve with its muscle led to a clearly noticeable, although much smaller, contraction than with the participation of metals. This was the first recording of bioelectric phenomena on which modern electrodiagnostics of the cardiovascular and a number of other human systems is based.

Volta is trying to unravel the nature of the unusual phenomena discovered. He clearly formulates the following problem for himself: “What is the cause of the emergence of electricity?” I asked myself in the same way as each of you would do it. Reflections led me to one solution: from the contact of two dissimilar metals, for example, silver and zinc , the balance of electricity in both metals is disturbed. At the point of contact of the metals, positive electricity is directed from silver to zinc and accumulates on the latter, while negative electricity is concentrated on silver. This means that electrical matter moves in a certain direction. placed silver and zinc plates on top of each other without intermediate spacers, that is, the zinc plates were in contact with the silver ones, then their overall effect was reduced to zero. To enhance the electrical effect or sum it up, each zinc plate should be brought into contact with only one silver one. and fold sequentially greatest number steam. This is achieved precisely by placing a wet piece of cloth on each zinc plate, thereby separating it from the silver plate of the next pair." Much of what Volta said does not lose its significance even now, in the light of modern scientific ideas.

Unfortunately, this dispute was tragically interrupted. Napoleon's army occupied Italy. For refusing to swear allegiance to the new government, Galvani lost his chair, was fired and soon died. The second participant in the dispute, Volta, lived to see the full recognition of the discoveries of both scientists. In a historical dispute, both were right. Biologist Galvani entered the history of science as the founder of bioelectricity, physicist Volta - as the founder of electrochemical current sources.

Herald of the era of electrical engineering Alessandro Volta

To the 200th anniversary of the first source of electric current

Jan Schneiberg, D. Charlet

Alessandro Volta was, as they now say, an iconic figure in the history of electricity, electrical engineering, and telecommunications.

By the last quarter of the 18th century, much was already known about the properties of the mysterious “electric force”. Electrostatic friction machines were designed to produce electrical charges (Francis Gouxby, England), the phenomenon of electrical conductivity was discovered (Stephen Gray, England) and the concept of two types of electricity was given - “glass” and “resin” - subsequently “positive” and “negative” ( Charles Dufay, France). A storage device for electric charges was created - the first capacitor, the so-called "Leyden jar" (Ewald Kleist, Pomerania, and Pieter van Mussenbroek, Holland), lightning was "tamed" (B. Franklin, USA) by using a lightning rod (in everyday vocabulary "lightning rod") . Finally, the First Law of Electrostatics was established (Charles Coulomb, France).

But the epoch-making discovery of Volta - “contact electricity” - seemed to sum up all the previously achieved results and gave a powerful impetus to new, more in-depth research into the nature of electricity and its possibilities. practical application.

Alessandro Volta was born on February 18, 1745 on the family estate of his ancestors, near the small town of Como in northern Italy. He comes from an aristocratic family, his mother was Duchess Maddalena Inzai. In his earliest years, Alessandro suffered from delayed physical and mental development; he began to speak only at the age of four. Then its development went very quickly. Contrary to the career of a clergyman destined for him, he became interested in physical experiments and, already at the age of 18, corresponded with one of the most prominent electrical physicists of the time, a demonstrator of spectacular public electrical experiments Abbot Jean Nollet.

Alessandro Volta

From 1774 to 1779 Volta is a physics teacher at the Royal School of Como. At the age of 26 he releases his first scientific work"Empirical studies of methods for exciting electricity and improving the design of machines." He made his first serious invention in 1772. It was the so-called condenser electroscope with diverging straws (connecting an electroscope with a capacitor), which had much greater sensitivity than previous electroscopes with cork or elderberry balls suspended on threads. The device had metric properties, since the deflection of the straws by an angle of up to 30° turned out to be proportional to the charge of the electroscope. The electroscope was for many years the main measuring instrument used by Volta himself and other researchers.

At the age of thirty, Volta became famous. He invented the resin electrophore, or, as the inventor himself called it, “elettrophoro perpetuo,” which means “permanent carrier of electricity.” The electrophoric machine used the phenomenon of electrification through induction, while in the electrostatic machines used, electricity was produced by friction. The device is extremely simple and also extremely original. It consists of two metal disks. One, let’s say the bottom one, is covered with a layer of resin. When rubbed with your hand, leather glove or fur, the disc is charged with negative electricity. If you bring the upper disk to it, the latter will charge as shown in Fig. 1 a. When unbound electricity is discharged into the ground (Fig. 1 b), at least with the experimenter’s finger, the upper disk will be positively charged. You can lift it and remove the charge from it (Fig. 1 c). By repeating the cycle of lowering and raising the upper disk many times, you can increase the charge just as many times.

Rice. 1. Diagram explaining the operation of Volta's electrophore

Volta indicated that his electrophore “continues to work even three days after charging.” And further: “My machine makes it possible to obtain electricity in any weather and produces an effect more excellent than the best disk and ball (electrostatic - author's note) machines." So, an electrophore is a device that makes it possible to obtain powerful discharges of static electricity. Volta extracted from it "sparks ten or twelve finger thicknesses and even more...". Volta's electrophore served as the basis for the construction of a whole class of induction, so-called "electrophores" ", cars.

Polemical commentary. Some historians of physics and electrical engineering believe that Volta did not invent the electrophore, but only improved a device invented earlier by the St. Petersburg academician Franz Epinus. Indeed, in 1758, Epinus proposed the theory of transmitting “electricity through influence” - by the method of electrostatic induction, i.e., in modern terminology, he invented a method. He also built the first device proving this possibility. It consisted of a metal bowl into which a molded mass of electrified sulfur was inserted and then removed. Both the cup and the sulfur turned out to be electrically charged.

However, Epinus did not go beyond a laboratory demonstration, and the device he invented did not receive practical application. Volta, on the basis of the method invented by Epinus, invented an original electrophore, which gives a new technical effect in comparison with the prototype, which, according to all the canons of patent law, is recognized as an invention. This is typical for the history of technology. Once invented, the method made it possible to use its principle to create, that is, invent, various devices. For example, P. Schilling invented a method of electromagnetic telegraphy and the first device for its implementation. Then, on the same principle, C. Wheatstone and W. Cook invented the pointer telegraph, and Morse invented the printing telegraph. All of them are rightfully considered inventors.

Volta himself admitted that Apinus realized the idea of ​​an electrophorus, but did not construct a complete device.

In 1776, Volta invented a gas pistol - the “Volta pistol”, in which methane gas exploded from an electric spark.

In 1779, Volta was invited to take the chair of physics at a university with a thousand-year history in the city of Pavia, where he worked for 36 years.

A progressive and courageous professor, he breaks with in Latin and teaches students from books written in Italian.

Volta travels a lot: Brussels, Amsterdam, Paris, London, Berlin. In every city, meetings of scientists greet him, celebrate him with honors, and present him with gold medals. However, Volta’s “finest hour” is still ahead; it will come in more than two decades. In the meantime, he moves away from electricity research for fifteen years, lives a measured life as a professor and is engaged in various things that interest him. At the age of over forty, Volta married the noble Teresa Pellegrina, who bore him three sons.

And now - a sensation! The professor comes across Galvani’s just-published treatise “On Electrical Forces in Muscular Movement.” The transformation of Volta's position is interesting. At first, he perceives the treatise with skepticism. Then he repeated Galvani’s experiments and already on April 3, 1792 he wrote to the latter: “... since I became an eyewitness and observed these miracles, I, perhaps, have moved from distrust to fanaticism.”

However, this state did not last long. On May 5, 1792, in his university lecture, he extols Galvani’s experiments, but the very next lecture, on May 14, is carried out in a polemical manner, expressing the idea that the frog is most likely only an indicator of electricity, “an electrometer, tens of times more sensitive than even the most sensitive electrometer with gold leaves."

Soon the keen eye of the physicist notices something that did not attract the attention of the physiologist Galvani: the trembling of the frog's legs is observed only when it is touched by wires made of two different metals. Volta suggests that the muscles do not participate in the creation of electricity, and their contraction is a secondary effect caused by the stimulation of the nerve. To prove this, he performs a famous experiment in which a sour taste is detected on the tongue when a tin or lead plate is applied to its tip, and a silver or gold coin is applied to the middle of the tongue or to the cheek and the plate and coin are connected with a wire. We feel a similar taste when we lick two battery contacts at the same time. The sourish taste turns into an “alkaline” one, that is, giving off a bitter taste, if metal objects are swapped on the tongue.

In June 1792, just three months after Volta began repeating Galvani’s experiments, he no longer had any doubts: “Thus, metals are not only excellent conductors, but also engines of electricity; they not only provide the easiest path passing electrical

fluid, ... but they themselves cause the same imbalance by extracting this fluid and introducing it, similar to what happens when rubbing idioelectrics" (this is what they called bodies that were electrified by friction in the time of Volta - author's note).

So Volta established the law of contact stresses: two dissimilar metals cause an “equilibrium imbalance” (in modern terms, they create a potential difference) between both, after which he proposed calling the electricity obtained in this way not “animal”, but “metallic”. This began his seven-year journey to a truly great creation.

The first series of unique experiments to measure contact potential differences (CPD) resulted in the compilation of the famous “Volta series”, in which the elements are arranged in the following sequence: zinc, tin foil, lead, tin, iron, bronze, copper, platinum, gold, silver, mercury , graphite (Volta mistakenly classified graphite as a metal - author's note).

Each of them, coming into contact with any of the subsequent members of the series, receives a positive charge, and this subsequent one receives a negative charge. For example, iron (+) / copper (-); zinc (+) / silver (-), etc. Volta called the force generated by the contact of two metals electroexcitatory, or electromotive force. This force moves electricity so that a voltage difference is created between the metals. Volta further established that the voltage difference will be greater the further the metals are located from one another. For example, iron/copper - 2, lead/tin - 1, zinc/silver - 12.

In 1796-1797 An important law was revealed: the potential difference between two terms of a series is equal to the sum of the potential differences of all intermediate terms:

A/B + B/C + C/D + D/E + E/F = A/F.

Indeed, 12 = 1 + 2 + 3 + 1 + 5.

In addition, experiments have shown that voltage differences do not occur in a “closed series”: A/B + B/C + C/D + D/A = 0. This meant that through several purely metallic contacts it was impossible to achieve higher voltages than with direct contact of only two metals.

From a modern point of view, the theory of contact electricity proposed by Volta was erroneous. He counted on the possibility of continuously obtaining energy in the form of galvanic current without expending any other type of energy.

Still, at the end of 1799, Volta managed to achieve what he wanted. He first established that when two metals come into contact, one receives more stress than the other. For example, when connecting copper and zinc plates, the copper plate has a potential of 1, and the zinc plate has a potential of 12. Numerous subsequent experiments led Volta to the conclusion that a continuous electric current can only arise in a closed circuit composed of various conductors - metals (which he called first-class conductors) and liquids (which he called second class conductors).

Thus, Volta, without fully realizing it, came to the creation of an electrochemical element, the action of which was based on the conversion of chemical energy into electrical energy.

Rice. 2. Types of galvanic cells depicted by Volta in a letter to Banks: above - a cup battery, below - variants of “voltaic pillars”.

Volta was able to obtain significant voltages by placing a column of circles of identical contact pairs of metals, identically oriented and separated by wet fabric spacers. Volta himself illustrated the essence of this using the example of his cup battery (Fig. 2 above). In the left cup there is one copper plate, its potential is 1. In the next three cups, the left plates are zinc, the right ones are copper; in the last cup - zinc; each zinc one in one cup is connected by a metal bow to a copper one in the next cup. The first zinc plate has a potential of 12. Volta assumed that two metal plates separated by a liquid acquire the same potential. Consequently, the second copper will also have a potential of 12, and the second zinc will have a potential of 12 + 11 = 23; third zinc 12 + 2 * 11 = = 34; the fourth 12 + 3 * 11 = 45, etc. For example, the 10th zinc will acquire the potential of 12 + 9 * 11 = 111.

Volta reported his discovery in a letter dated March 20, 1800 to the President of the Royal Society of London, Joseph Banks. In the message “On electricity excited by simple contact of simple conducting substances” he writes: “... I... have the pleasure of reporting some amazing results that I have obtained. The main one of these results... is the creation of a device that operates continuously... ., creates an indestructible charge, gives a continuous impulse to the electrical fluid." And further: “The projectile of which I speak - and this will surprise you - ... is nothing more than a collection of good conductors of various kinds, arranged in a certain way. Twenty, forty or sixty circles of copper or, even better, silver, each folded with a circle of tin or better zinc, and the same number of layers of water or some other liquid that conducts better than water, for example, saline solution, lye, etc., or pieces of cardboard, leather, etc., well moistened these liquids, and these layers are located between both dissimilar metals of each pair. This is all that makes up my new instrument." Volta himself initially proposed calling his device, or projectile, or instrument an “artificial electric organ,” then renamed it an “electromotive column.” Later, the French began to call this device a “galvanic column” or “voltaic column”.

Volta was responsible for introducing the concepts of “capacitance”, “circuit”, “electromotive force”, “voltage difference”.

Honor and fame came to the inventor. In France, a medal is minted in his honor, and the first consul of the Directory, General Bonaparte, establishes a fund of 200,000 francs for “brilliant discoverers” in the field of electricity and awards the first prize to the author of the pillar. Volta becomes a knight of the Legion of Honor, the Iron Cross, receives the title of senator and count, becomes a member of the Paris and St. Petersburg Academies of Sciences, a member of the Royal Society of London, which awards him the Coplay Gold Medal.

The creation of the "voltaic column" was a revolutionary event in the science of electricity, it prepared the foundation for the emergence of modern electrical engineering and had a huge impact on the entire history of human civilization. It is not surprising that Volta’s contemporary, French academician D. Arago, considered the Voltaic column “... the most remarkable device ever created by people, not excluding the telescope and the steam engine.”

In the first third of the 19th century, the “Volta Column” remained the only source of electric current, which was successfully used for their experiments and discoveries by major scientists - V. Petrov, X. Davy, A.-M. Ampere, M. Faraday.

Among them, the first to improve the “voltaic column” was Vasily Petrov, a professor of physics at the St. Petersburg Medical-Surgical Academy. He pointed out that more intense current could be obtained from a more powerful battery. In 1802, he created a unique high-voltage current source (about 1700 V), which he called a “huge battery.” This battery consisted of 2100 copper-zinc cells (the batteries that existed in Europe at that time had 15-20 elements). In his essay “News of Galvani-Volta Experiments,” published in 1803, V. Petrov described the phenomenon of the electric arc discovered by him and indicated that with its “bright light, similar to sunlight or a flame, a dark room can be quite clearly illuminated.” This marked the beginning of two directions: the electric smelting of metals and their recovery from ores and the creation of electric arc lamps.

Volta was lucky to live to see most important discoveries, made using his invention: this is the action of current on a magnetic needle, the mutual rotation of conductors with current and a magnet (the prototype of an electric motor), Ampere’s development of the fundamentals of electrodynamics. In 1819 Volta left his professorship.

He died in his native city in 1827 at the age of 82 years.

Legends about Volta circulated during his lifetime. To prove his theory about “contact electricity,” in 1794 he conducted the “Wet Quartet” experiment. Four men with wet hands stood in a circle. Then the first took the zinc plate with his right hand, and touched the tongue of the second with his left; the second touched the eyeball of the third, who held the dissected frog by the legs, and the fourth grabbed its body with his right hand, and with his left brought the silver plate to the zinc plate, which the first was holding with his right hand. At the moment of contact, the first one shuddered sharply, the second winced from the “lemon” taste in his mouth, the third got sparks from his eyes, the fourth felt unpleasant sensations, and the frog seemed to come to life and tremble. This sight shocked eyewitnesses.

Volta's scientific contribution was highly appreciated by his contemporaries - he was considered the greatest physicist in Italy after Galileo. Based on Volta’s invention, until the end of the 19th century, about two hundred varieties of “Voltaic column” - electrochemical current sources - were proposed.

The memory of Volta was immortalized in 1881 at the International Congress of Electricians in Paris, where one of the most important electrical units - the unit of voltage - was given the name "volt".

The creation of the “voltaic column” ended the era of electrostatics and marked the beginning of the era of electrical engineering.

So at the turn of the 18th-19th centuries there was a transition from electricity for science to electricity for humanity - for industry, everyday life, and culture.

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