The Baghdad Battery or Parthian Battery is a set of three artifacts which were found together: a ceramic pot, a tube of copper, and a rod of iron. It was discovered in modern Khujut Rabu, Iraq, close to the metropolis of Ctesiphon, the capital of the Parthian (150 BC – 223 AD) and Sasanian (224–650 AD) empires, and it is considered to date from either of these periods.

Its origin and purpose remain unclear. It was hypothesized by some researchers that the object functioned as a galvanic cell, possibly used for electroplating, or some kind of electrotherapy, but there is no electroplated object known from this period. An alternative explanation is that it functioned as a storage vessel for sacred scrolls.

Physical description and dating The artifacts consist of a terracotta pot approximately 130 mm (5 in) tall (with a one-and-a-half-inch mouth) containing a cylinder made of a rolled copper sheet, which houses a single iron rod. At the top, the iron rod is isolated from the copper by bitumen, with plugs or stoppers, and both rod and cylinder fit snugly inside the opening of the jar. The copper cylinder is not watertight, so if the jar were filled with a liquid, this would surround the iron rod as well. The artifact had been exposed to the weather and had suffered corrosion.

Theories concerning operation Its origin and purpose remain unclear. Wilhelm König was an assistant at the National Museum of Iraq in the 1930s. He had observed a number of very fine silver objects from ancient Iraq, plated with very thin layers of gold, and speculated that they were electroplated. In 1938 he authored a paper offering the hypothesis that they may have formed a galvanic cell, perhaps used for electroplating gold onto silver objects.[1] This interpretation is rejected by skeptics.

Some believe that wine, lemon juice, grape juice, or vinegar was used as an acidic electrolyte solution to generate an electric current from the difference between the electrode potentials of the copper and iron electrodes.

Supporting experiments After the Second World War, a man named Willard Gray demonstrated current production by a reconstruction of the inferred battery design when filled with grape juice. W. Jansen experimented with benzoquinone (some beetles produce quinones) and vinegar in a cell and got satisfactory performance.

In 1978, Arne Eggebrecht reportedly reproduced the electroplating of gold onto a small statue. There are no (direct) written or photographic records of this experiment. The only records are segments of a television show.

Controversies over Battery hypothesis

The artifacts do not form a useful battery for several reasons:     

1.    Gas is evolved at an iron/copper/electrolyte junction. Bubbles form a partial insulation of the electrode. Thus the battery's functionality decreases the more it is used.     

2.    Although several volts can be produced by connecting batteries in series, the voltage generated by iron/copper/electrolyte cell is below 1 volt. Also the jar was sealed with asphalt, making it enormously difficult to refill the liquid electrolyte, and the presumed “battery” also has no terminals. The iron rod did project outside of the asphalt plug, but the copper tube did not, making it impossible to connect wires to make a circuit.

Electroplating hypothesis

König himself seems to have been mistaken on the nature of the objects he thought were electroplated. They were apparently fire-gilded (with mercury). Paul Craddock of the British Museum said "The examples we see from this region and era are conventional gold plating and mercury gilding. There’s never been any irrefutable evidence to support the electroplating theory".

Paul T. Keyser of the University of Alberta noted that Eggebrecht used a more efficient, modern electrolyte, and that using only vinegar, or other electrolytes available at the time assumed, the battery would be very feeble, and for that and other reasons concludes that even if this was in fact a battery, it could not have been used for electroplating. However, Keyser still supported the battery theory, but believed it was used for some kind of mild electrotherapy such as pain relief, possibly through electroacupuncture.

Bitumen as an insulator

A bitumen seal, being thermoplastic, would be extremely inconvenient for a galvanic cell, which would require frequent topping up of the electrolyte (if they were intended for extended use).

Alternative hypothesis

The artifacts strongly resemble another type of object with a known purpose – storage vessels for sacred scrolls from nearby Seleucia on the Tigris. Since these vessels were exposed to the elements, it is possible that any papyrus or parchment inside had completely rotted away, perhaps leaving a trace of slightly acidic organic residue. Although the Seleucia vessels do not have the outermost clay jar, they are otherwise almost identical.

The object was looted along with thousands of other artifacts from the National Museum during the 2003 invasion of Iraq.

In March 2012, Professor Elizabeth Stone of Stony Brook University, an expert on Iraqi archaeology, returning from the first archaeological expedition in Iraq after 20 years, stated that she does not know a single archaeologist who believed that these were batteries.

Despite the skepticism though, there is no reason why a battery couldn't have existed 2000 years ago. We like to think that we are smarter than any other civilization before us. But that's just not the case. People may have used different technology before, but this technology solved their problems as much as our technology solves ours. Maybe the 1.5 volts was enough for what this device was made for? Maybe there were other devices like this which we haven't discovered.


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