Baghdad Battery
The Baghdad Battery is what appears to be a fully functional battery from somewhere between 250 BC and 250 found in Khujut Rabu outside Baghdad. It consists of a jar, inside which a copper cylinder and an inner iron bar, isolated from the copper by asphalt resides.In 1938, the German archaeologist Wilhelm Konig discovered a five inch long (or 13 cm) clay jar containing a copper cylinder (some reports say it was found in the collections of the National Museum of Iraq). The cylinder covered and protected a iron rod. The Battery had been exposed to the weather and had suffered corrosion. It was located in Khujut Rabu, near Baghdad, Iraq. Konig thought the mechanism looked like a battery and published a paper about it in 1940. Upon publication, his discovery was discounted by the scientific community and soon disregarded.
After the second world war, Willard Gray built a reproduction of the battery and proved it to work if filled with some sour substance like grape juice. Subsequent tests indicated acidic substances in the item. These substances that may have exerted some effect were analysed as having been vinegar, wine, or another electrolytic solution.
More recently, the batteries of Baghdad have attracted new interest. Some regard the Baghdad Battery as an anachronism, in the sense that the Baghdad Battery appears to be out of place in time.
The practical uses of this battery is uncertain. The most common guess is that the Parthians living in this area used it to electroplate metallic items, i.e. put a thin layer of e.g. gold over an object made out of some other metal. It also appears that similar batteries can be located around ancient Egypt, where objects with traces of precious metal electroplating have been discovered at different locations.
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