Electrochemistry

Electrochemistry - Electrochemistry A little history Some...

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Electrochemistry A little history: Some of you will be familiar with the story of Luigi Galvani and his discovery of “animal electricity”. The phenomenon of “static” electricity had been known for centuries – insulating materials such as amber or glass, rubbed vigorously with rabbit’s fur, for example, became electrically charged and could deliver a mild electric shock or a tiny spark – we still experience this today. (Incidentally, you need about 10,000 volts per centimeter to drive a spark through the air, so a spark of about 1 mm that you can generate by scuffling your feet on the carpet on a dry day means that you have charged yourself up to 1,000 volts or so.) The reason that voltages of several kilovolts are just mildly interesting rather than acutely shocking is that the associated currents are very low. By the mid-18th century various static electricity machines had been invented that could generate significant voltage. Galvani was a physician and President of the University of Bologna in Italy. In 1783 while dissecting a frog Galvani’s assistant happened to touch a nerve that caused the frog leg to twitch. Later a similar effect was shown to occur when a scalpel attached to a static electricity machine touched a nerve. Galvani took these observations to build a theory of “animal electricity” – something different from static electricity and, he thought, intrinsic to the animal. Using static electricity to deliver stronger jolts, Galvani found that he could stimulate nerves and cause muscles to contract in larger animals – the tails of dead dogs or cats could be made to twitch, for example, and this soon became the subject of public displays to theaters full of people. The ultimate animal of course was human, and enterprising scientific entertainers went so far as to obtain the corpses of freshly-executed criminals. Placed on a table in front of the audience, clever application of electrical stimulus to the right nerve point could cause an arm or a leg to rise and – the climax – stimulating the stomach muscles could actually cause the corpse to begin to sit up: the motion compressed the diaphragm and so this ghastly motion was accompanied with an unearthly groan as air was forced out of the lungs. Box office gold! Mary Shelley was influenced by such exhibitions to write the novel “Frankenstein” (first published in 1818) about the mad scientist who constructs an electrically animated monster. Galvani’s colleague and competitor Alessandro Volta was Professor of Physics at the University of Pavia. Volta was skeptical about the idea of animal electricity, suspecting instead that the effect arose from the dissimilar metals used in the dissection – steel scalpel, copper sheeting covering the dissecting table – when they were connected through the saline fluid in the frog leg.
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Electrochemistry - Electrochemistry A little history Some...

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