May 28, 2009 at 4:06 pm (Metallurgy, Technology, The Ancient World, The Arab World) (alessandro volta, ancient technology, babylonian, babylonian technology, baghdad battery, early battery, history of electricity, irrational geographic, museum of baghdad)
In the mid 1930s a series of curious objects, believed to date from the 3rd century BC, were unearthed in Khujut Rabu, near Baghdad. These earthenware jars, measuring about 5 inches high, contained copper cylinders and iron rods. This strange group of objects, not given any special attention, found its way into the collection of the National Museum of Iraq. It was not until several years later that Wilhelm Konig, the museum’s director, came across these jars and pieces of metal and, upon analyzing them, drew a startling conclusion.
In 1940 Konig published a paper contending that when the pieces of these artifacts were fitted together correctly and the jars were filled with an acidic solution, they formed functional electrochemical cells capable of generating electricity. While modern historians attribute the invention of the battery to Italian physicist Alessandro Volta in 1800, Volta may have simply recreated a 2,000 year-old lost technology. (Cultures dating as far back as 2,750 BC made written mention of electricity, although only regarding electricity that occurs naturally. It wasn’t until the 17th and 18th centuries that serious academic inquiries into electricity were conducted by Western scientists, notably William Gilbert and Benjamin Franklin.)
The Baghdad batteries, Konig believed, worked in the same way as the Voltaic pile. This theory is supported by the fact that the iron rods discovered inside the earthenware jars do in fact show evidence of acidic corrosion, perhaps having been submerged in vinegar. Konig suggested that when the iron rods were inserted into the copper cylinders, fitted into the jars’ mouths with asphalt stoppers, and the jars were filled with vinegar, the resulting cells were in fact capable of producing an electrical current. This claim was proved in 1940 by Willard F. M. Gray of the General Electric High Voltage Laboratory in Pittsfield, MA. Making an exact replica of the devices unearthed at Khujut Rabu and using a copper sulfite solution, Gray generated a half a volt of electricity.
Later experiments using grape juice and vinegar produced similar results. Even the popular television program Mythbusters successfully recreated Gray’s experiment in 2005. While the voltage generated by these batteries is meager (never more than 1V), it has been hypothesized that if several of them were wired together as were the zinc and copper rods in Voltaic piles, higher voltage could be achieved.
Konig cited examples of artifacts electroplated with gold, dating from the same era as the batteries, as evidence of the use of low-voltage electricity in the 3rd century BC. By negatively charging a piece of metal with an electrical current and submerging it in a solution of metal salt, it becomes coated with a layer of positive metal ions. This technique has been used, for example, in the process of gold plating. Gold-coated Egyptian artifacts dating contemporaneously with the Baghdad batteries might support this interpretation of the batteries’ use.
In the years since Konig published his paper in 1940, there has been much debate about the batteries in the scientific community. With some factions contending that the notion of ancient electricity is farcical and others going so far as to claim that the Baghdad batteries explain the legendary powers of the Biblical Ark of the Covenant, a wide range of viewpoints have been expressed. Since ancient texts never explicitly confirm knowledge of usable electrical energy, modern historians are doomed to continue speculating about the role, if any at all, that controlled electricity played in ancient Babylonia. But when pondering objects that have the potential to drastically redefine our conception of ancient history, as with the Piri Reis map discussed in a previous entry, an open mind is certainly the most suitable tool.
Some Further Reading: