Voltaic pillar

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Schematic structure of a Voltaic column

The voltaic pile or Volta column is one of Alessandro Volta 1799/1800 and developed in 1800 at the Royal Society in London the public presented arrangement today as a precursor batteries in the 19th century is of great importance as a power source had. It consists of many copper and zinc flakes layered on top of one another , between which pieces of cardboard or leather soaked in electrolyte are placed in a regular sequence . Silver was used instead of copper and tin was used instead of zinc .

A single element of the voltaic column is called the volta element . It consists for example of a copper foil, an electrolyte layer and a zinc foil. It supplies only a low voltage, which is why many such elements are stacked on top of each other in the column. This results in the stacking sequence copper, electrolyte, zinc, copper, electrolyte and again zinc, i.e. This means that copper and zinc alternate and in this example the electrolyte is always between copper (below) and zinc (above).

meaning

Voltaic column

The Voltaic Column can be classified as one of the most important inventions, as it was the first usable continuous power source to enable research into electricity - long before the invention of the electric generator . The Voltaic column paved the way for electrical engineering as well as electronics and many other technical areas, such as electroplating . The voltaic column was the first significant battery and enabled the discovery of electrolysis and thus the first depiction of many base elements , in particular the metals sodium , potassium , barium , strontium , calcium and magnesium by Humphry Davy in 1807 and 1808. Also the first attempts to transmit messages by means of electrical telegraphy were only possible with the invention of Volta.

Application in technology

With the help of the Voltaic column or successors and the arcs generated with it, electrical lighting with arc lamps was implemented. Arc lamps are the oldest sources of electrical light. Johann Samuel Halle (1792) and the British Humphry Davy (1802) observed the effect of the arc and used it for lighting. Brass or graphite electrodes were used, the graphite electrodes burning off relatively quickly.

One of the first applications in ship technology came from Moritz Hermann von Jacobi , who propelled the first electric boat in Saint Petersburg in 1839 with the help of a lying Voltaic column and an electric motor developed and built by him . The tests were carried out on the St. Petersburg canals and the Neva and approved by a state commission.

Use in medicine

As early as 1801, a large number of attempts to use the voltaic column medicinally were reported. For example, it has been suggested to use them to distinguish dead and seemingly dead . Despite some alleged successes, the therapeutic application, galvanotherapy , remained limited at the time because of the effects that were still largely not understood. Galvanotherapy was later developed by Golding Bird and Robert Remak .

functionality

The voltaic column is a series of galvanic cells connected in series . At the negative pole, which is the anode here , since the oxidation takes place here, the less noble metal dissolves: The zinc platelet dissolves: Every zinc atom that goes into solution as a zinc ion releases two electrons; This creates an excess of electrons in the zinc electrode , which is why it forms the negative pole.

Several reactions are possible on the positive electrode, the cathode , since the reduction takes place here. In the case of copper plates that have not been polished, they are covered with an oxide layer. Then the reduction takes place first. This can also occur if the copper has dissolved due to the presence of atmospheric oxygen.

The voltaic column also works when polished copper or silver are used as electrodes, i.e. when there are no copper or silver ions at all. Then oxygen from the air is reduced on copper or silver: If you use an acidic electrolyte (e.g. vinegar or dilute sulfuric acid or hydrochloric acid) instead of a neutral electrolyte (e.g. salt water), hydrogen ions are reduced on copper or silver . There is little hydrogen evolution at the zinc electrode because it is inhibited there: hydrogen has a significantly greater overvoltage on zinc than on copper or silver.

A major disadvantage of the Voltaic column is due to the vertical structure in the form of a column. Due to the dead weight of the stacked metal plates, the soft pieces of cardboard or leather that are inserted between the metal plates and soaked with electrolyte are pressed together. As a result, the liquid electrolyte, in particular in the lower region of the column, is pressed outwards and the battery capacity of the entire arrangement is reduced. The technical advancement of the Voltaic column from 1802, which avoids this disadvantage, is the trough battery by William Cruickshank .

Reaction equations

As with all batteries with a zinc electrode, zinc dissolves from this anode when it is discharged:

There is always a layer of oxidation products such as B. copper oxides if the copper was in contact with air. Thus there are copper ions on the surface that can be discharged:

In the Daniell element , the same reactions take place, but much longer, as the addition of copper salts results in a much larger supply of copper ions. These will soon be used up in the voltaic column. The main reaction then takes place on the copper electrode

from. But it delivers a lower voltage. The overall reaction results

.

To a lesser extent, there is also a reaction of the oxygen in the air at the copper electrode

possible, especially if the electrolyte of a freshly built column is saturated with air. Since the oxygen is consumed and only slowly diffuses into the interior of the cell, this reaction is of secondary importance when the cell is operated for a long time and with higher currents. Nevertheless, according to the reaction equation, the column consumes oxygen from the surrounding air during operation. Oxygen helps make the column more efficient. On the other hand, oxygen is dispensable for the effectiveness of the column, since the hydrogen evolution indicated above can also take place instead of the oxygen reduction. Oxygen can also consume zinc from the zinc electrodes due to corrosion and destroy them in this way:

Volta's structure

Volta's original cells each had a further copper or zinc plate at the end, which are not shown in the schematic picture above and which did not contribute to the tension in the column.

Web links

Commons : Voltaic Pillar  - Collection of Images

literature

  • Bern Dibner: Alessandro Volta and the electric battery . Verlag F. Watts, 1964, LCCN  64-011915 , p. 135 ( limited preview in Google Book search).

Individual evidence

  1. a b Alexander Volta: On the Electricity excited by the mere Contact of conducting Substances of different kinds. In a Letter from Mr. Alexander Volta, FRS Professor of Natural Philosophy in the University of Pavia, to the Rt. Hon. Sir Joseph Banks Bart. KBPRS Read June 26, 1800. In: Royal Society (Ed.): Philosophical Transactions of the Royal Society of London . tape 90 , no. 2 (Part II). W. Bulmer, 1800, ISSN  0261-0523 , OCLC 7134330 , XVII: Philosophical Transactions, p. 403–431 , doi : 10.1098 / rstl.1800.0018 , JSTOR : 107060 (French, ia600307.us.archive.org [PDF; 3.7 MB ; retrieved on July 17, 2016] stated letter date: March 20, 1800): “mon premier appareil a column […] les plateaux métalliques […] l'appareil d'un nombre tres-grand de plateaux, au-dela, par example , de 60, 80, 100 […] »
  2. Alexander Volta: On the Electricity excited by the Mere Contact of Conducting Substances of Different Kinds . In a Letter from Mr. Alexander Volta, FRS Professor of Natural Philosophy in the University of Pavia, to the Rt. Hon. Sir Joseph Banks Bart. KBPRS Read June 26, 1800. In: Royal Society of London (Ed.): Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London . From 1800 to 1830 inclusive. 1 (1800 to 1814). Richard Taylor, London 1832, p. 27–29 , JSTOR : 109515 (English, biodiversitylibrary.org [accessed on July 17, 2016] French: ds . 1800.): “The object of the present paper is to describe this apparatus […] It consists of a long series of alternate succession of three conducting substances, either copper, tin and water; or, what is much preferable, silver, zinc, and a solution of any neutral or alkaline salt. "
  3. a b Leopold Franz Herrmann: System der practical Arzeneymittellehre . First volume, Allgemeine Arzeneymittellehre. tape 1 . Ghelen, Vienna 1824, Part I, § 7. Physical Remedies, p. 25–26 ( limited preview in the Google book search [accessed on July 15, 2016]. Works by Karl Johann Christian Grapengiesser Berlin 1801, Franz Heinrich Martens 1803 and JA Heidemann Vienna 1808) are cited : “Significant gaps […] only permitted a more restricted arbitrary application of some of them for the sake of the healing business. "
  4. ^ Joh. Anton Heidmann: Results from my experiments with the composite, dissimilar metal compound, or with the Voltaic column . In: Ludwig Wilhelm Gilbert (Ed.): Annalen der Physik . tape 10 , no. 1 . Renger, Hall 1802, p. 50–56 , doi : 10.1002 / andp.18020100105 ( online at Gallica [accessed on July 24, 2016]): “The easiest and most reliable determination of true death and the differentiation between it and apparent death from the application of reinforced galvanism to people who have only died can be expected "
  5. a b c Jean-Baptiste Biot , Frédéric Cuvier : About the ingestion of oxygen gas through the voltaic column . In: Ludwig Wilhelm Gilbert (Ed.): Annalen der Physik . tape 10 , no. 2 . Renger, Hall 1802, p. 161–165 , doi : 10.1002 / andp.18020100203 ( online at Gallica ): “You can see from this experiment that the oxygen which the column removes from the atmospheric air helps to increase the effectiveness of the column. [...] We conclude from this that the voltaic column has a peculiar effectiveness that is independent of the external air. "