Madame Lucia Galcazzi Galvani was, according to the general belief, a very remarkable beauty and ones this lady got a very strong cold. The physicians prescribed her to eat frog-soup. Her husband, professor of anatomy Luigi Aloisio Galvani once noticed, that the frog legs jerk as soon as a flake flares up out of the friction-electricity. The legs had to be not far from this electricity. Galvani gathered from this, that there must be some “animal electricity” in the frog muscles. Another coincidence confirmed his belief: the legs were jerking even during a storm, when they were hanged up with cuprous hangers to a metal handrail. Later legs were put on a zinced dissection table and they moved when the scalpel touched them. This happened in Italian Bologna in 1780. He published his “discovery” 11 years later.
One of the enthusiasted admirers of Galvani was a university professor in Padova Alessandro Guiseppe Antonio Anastasio Volta. He learned about Galvani´s experiments even before their publishing. He repeated them many times with many alternates. He came to the conclusion in 1791: The electricity arises with the contact of two metals. He immediately imparted this fact to the Royal London Association and to Galvani, whom he respected a lot. For Galvani it was a very bitter truth …
However it was Galvani, who discovered this mysterious power. And therefore Volta named it in honour of its discoverer the galvanic current. This happened in 1796. But soon he realised, that he can do the experiments much better when he replaces the natural galvanic cell (steel scalpel and zinced dissection table) with the whole battery of cells composed by superimposing the silver and zinc strips of tin. These strips had to be inter-leafed with leafs of leather moisted with acidified solution (1800). And the first dry cell was born! Today the physics know it under the name Volt´s pillar. Also Napoleon Bonaparte knew it. He was very impressed by this invention. They say, that once he visited the Parisian National Library and stayed at the wreath under which this was written: “Au grant Voltaire”, he had been thinking for a while and then he cleared the three last letters …
Alessandro Volta demonstrates his battery (the sitting
man on the right is Napoleon Bonaparte)
(from page http://www.physics.lsa.umich.edu/106/content/battery/battery.html)
Today many kinds and types of galvanic dry cells do exist, some change the chemical energy into the electric energy. But the most often produced and used are so called Leclanche´s dry cells. These have got a depolisator and are irreturnable (they can’t be recharged, it is only possible to regenerate them with very low current). In these dry cells the negative electrode is the zinc pot, positive electrode is the carbon stick. The electrolyte is the chloride ammoniac thickened with a paste so that it could not be spilled. The depolisator is the mixture of manganese oxide and graphite, pressed in a bag around the carbon electrode. Its purpose is to clear away the polarising effects of the hydrogen, which is being eliminated on the carbon electrode. The hydrogen would cover the whole surface of the electrode and as an insolent it would corrupt the function of the cell (the amount of the removed current would decrease). The depolisator oxidises with its oxidising effects the hydrogen. This happens during the creation of water.
Except these cheapest and widely used dry cells, there also exist more efficient, but also more expensive ones, e.g. the alkaline dry cells.
Zincchloride mono-cell PRIMA
(from page http://www.bateria.cz/)