Electrochemistry

Electrochemistry started in 1786 with the discovery by the anatomist, Galvani, that a dead frog's leg would twitch when touched by two different metals at the same time! His fellow Italian, Volta, replaced the frog's leg with salty water and produced the first chemical cell which would drive an electric current in 1800. Mr. Volta used silver and zinc discs separated by a cloth soaked in salt solution. He stacked them in a pile to make a battery with a high voltage! A battery is called a pila in Italy, and means a set of electric cells.

Volta tried all the metals he could lay his hands on, touching them in pairs on his tongue and estimating the electrical effect by the unpleasantness of the sensation! He was thus able to arrange the metals in an electrochemical series, according to how much voltage they produced when separated by an acid or salt solution. Cells work by chemical reactions between the metals and the conducting liquid (electrolyte) where they are in contact. The reactions only occur when electrons (the bits of atoms responsible for their chemical behaviour) are conveyed from one metal to the other. The metals must be connected somehow for the electrons to get from one to the other, and it is this flow of electrons which is the useful electric current.

Michael Faraday advanced our knowledge of electrochemistry enormously in the 1840s. Look on the back of a £20 note to see a picture of him and a list of electrochemical terms he introduced. You can also see a picture there of an electromagnetic generator he invented, which then took over from batteries as the most important way of making electric currents flow! Designing successful electric cells is a difficult business - people have been trying to improve them for the past 200 years. There are now rechargeable cells, where the chemical reactions can be reversed by passing an electric current from somewhere else through the cell, making it ready to work again. There are also fuel cells which convert fuels and oxygen into electricity without burning them together. What we haven't produced yet is a battery which is light enough and powerful enough to run an electric car as far as a tank of petrol will. There is a fortune to be made by the person who manages it!

Electrochemistry

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