Baghdad Battery

Drawing of the three pieces.^[1]

The Baghdad Battery, sometimes referred to as the Parthian Battery, is the common name for a number of artifacts created in Mesopotamia, during the dynasties of Parthian or Sassanid or Persian Empire period (the early centuries AD), and probably discovered in 1936 in the village of Khuyut Rabbou'a, near Baghdad, Iraq. These artifacts came to wider attention in 1938 when Wilhelm König, the German director of the National Museum of Iraq, found the objects in the museum's collections. In 1940, König published a paper speculating that they may have been galvanic cells, perhaps used for electroplating gold onto silver objects.^[2][3] This interpretation is far from having widespread acceptance, but continues to be considered as at least a hypothetical possibility by some scientists.^[2] It is frequently cited by believers in extraterrestrial visitation, ancient astronaut theories and advocates of pseudoarchaeology theories,^[4] in particular, a chapter on the batteries appeared in Erich von Däniken's discredited book Chariots of the Gods?, leading to the theory being publicly described as a myth, and considered impossible or irrelevant.^[2][5][6] Along with other theories and explanations presented by von Däniken, it is considered by the mainstream archaeological academy as fringe science or even charlatanism, assuming von Däniken knows his presentations are skewed and mostly not true, but still advocating the theories for money or fame.^[7] Von Däniken, and other fringe science theorists further claimed that electricity was used in ancient times, for lighting the tower of Alexandria, the tunnels of the Egyptian pyramids and for other sites and uses, besides coin plating.^[8] If correct, the artifacts would predate Alessandro Volta's 1800 invention of the electrochemical cell by more than a millennium.^[2]

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.^[9][10]

Description and dating

The artifacts consist of terracotta pots approximately 130 mm (5 in) tall (with a one-and-a-half-inch mouth) containing a copper cylinder made of a rolled-up copper sheet, which houses a single iron rod. At the top, the iron rod is isolated from the copper by bitumen plugs or stoppers, and both rod and cylinder fit snugly inside the opening of the jar, which bulges outward toward the middle. 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, although mild given the presence of an electrochemical couple. This has led some to 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 electrochemical potentials of the copper and iron electrodes.^[2][11]

König thought the objects might date to the Parthian period (between 250 BC and AD 224). However, according to St John Simpson of the Near Eastern department of the British Museum, their original excavation and context were not well-recorded (see stratigraphy), so evidence for this date range is very weak. Furthermore, the style of the pottery (see typology) is Sassanid (224-640).^[2][11]

Most of the components of the objects are not particularly amenable to advanced dating methods. The ceramic pots could be analysed by thermoluminescence dating, but this has not yet been done; in any case, it would only date the firing of the pots, which is not necessarily the same as when the complete artifact was assembled.

Electrical

Copper and iron form an electrochemical couple, so that, in the presence of any electrolyte, an electric potential (voltage) will be produced. This is not a very efficient battery as gas is evolved at an electrode, the bubbles forming a partial insulation of the electrode so that although several volts can be produced in theory by connecting them in series, their internal resistance from the formation of the gas bubbles becomes so great that it severely limits the electrical current that can be produced from such a simple wet cell.

König had observed a number of very fine silver objects from ancient Iraq that were plated with very thin layers of gold, and speculated that they were electroplated using batteries with these as the cells. After the Second World War, Willard Gray demonstrated current production by a reconstruction of the inferred battery design when filled with grape juice.^[3] W. Jansen experimented with benzoquinone (some beetles produce quinones) and vinegar in a cell and got satisfactory performance.^[3]

However, even among those believing the artifacts to be electrical devices, electroplating as a use is not well-regarded today. 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."^[2] The gilded objects that König thought might be electroplated are now believed to have been fire-gilded (with mercury). Reproduction experiments of electroplating by Arne Eggebrecht consumed "many" reproduction cells to achieve a plated layer just one micrometre thick. There is no record of Eggebrecht's experiments,^[12] although in "Ancient Wisdom", episode 3 of The Arthur C. Clark's Mysterious World series, Eggebrecht seemingly shows a small silver statue immersed in a cyanide-gold solution. The statuette and solution are connected to a Baghdad Battery replica, "and indeed, in a matter of minutes, the bottom half of this silver statuette acquires the sheen of gold."^[13] Paul T. Kayser 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.^[11][14]

Non-electrical

Elizabeth Stone, archaeologist at Stony Brook University, says modern archaeologists do not believe the object was a "battery".^[9] Skeptic scientists such as Dr. Jonathan Reed, and archaeologist Ken Feder, see the electrical experiments as embodying a key problem with experimental archaeology, saying that such experiments can only show that something was physically possible, but do not confirm that it actually occurred. Further, there are many difficulties with the interpretation of these artifacts as galvanic cells:^[6][15][16]

• The bitumen completely covers the copper cylinder, electrically insulating it, so no current can be drawn without modifying the design.
• There are no wires or conductors with them.
• No electrical equipment is associated with them.
• A bitumen seal, being thermoplastic, is excellent for forming a hermetic seal for long-term storage. It would be extremely inconvenient, however, for a galvanic cell, which would require frequent topping up of the electrolyte (if they were intended for extended use).

The artifacts strongly resemble another type of object with a known purpose – storage vessels for sacred scrolls from nearby Seleucia on the Tigris. Those vessels do not have the outermost clay jar, but are otherwise almost identical. Since these vessels were exposed to the elements,^[2][17] it is possible that any papyrus or parchment inside had completely rotted away, perhaps leaving a trace of slightly acidic organic residue.^[6]

In the media

The idea that the terracotta jars in certain circumstances could have been used to produce usable levels of electricity has been put to the test at least twice. On the 1980 British Television series Arthur C. Clarke's Mysterious World, Egyptologist Arne Eggebrecht created a voltaic cell using a jar filled with grape juice, to produce half a volt of electricity, demonstrating for the programme that jars used this way could electroplate a silver statuette in two hours, using a gold cyanide solution. Eggebrecht speculated that museums could contain many items mislabelled as gold when they are merely electroplated.^[4][18] However, doubt has recently been cast on the validity of these experiments, which were not documented and which other researchers have been unable to replicate.^[2][19]

The Discovery Channel program MythBusters built replicas of the jars to see if it was indeed possible for them to have been used for electroplating or electrostimulation. On MythBusters' 29th episode (March 23, 2005), ten hand-made terracotta jars were fitted to act as batteries. Lemon juice was chosen as the electrolyte to activate the electrochemical reaction between the copper and iron. Connected in series, the batteries produced 4 volts of electricity. When linked in series the cells had sufficient power to electroplate a small token.^[5]

Archaeologist Ken Feder commented on the show noting that no archaeological evidence has been found either for connections between the jars (which were necessary to produce the required voltage) or for their use for electroplating.^[20] In fact, plating of the era in which the batteries are claimed to be have been used, have been found to be fire-gilded (with mercury).^[2]

See also

• Dendera light
• Galvanization
• History of electromagnetism
• History of the battery
• Leyden jar

References

Further reading

• Von Handorf, D E., Crotty, D. E., The Baghdad battery - myth or reality?. Plating and Surface Finishing (USA). Vol. 89, no. 5, pp. 84–87. May 2002
• Brian Haughton, "The Baghdad battery", Hidden History: Lost Civilizations, Secret Knowledge, and Ancient Mysteries, pages 129-132, Career Press, 2007 ISBN 1564148971.
• [0:4:25] (4 minutes 25 seconds) in Video of Arthur C Clark's Mysterious World - Episode 3: Ancient Aliens, showing Prof. Arno Eggebrecht experiments with a Baghdad Battery. Prof. Eggebrecht shows a hand-sized vessel filled with a half a cup of grape juice produced on the spot, as an acid, and the iron rod inserted in a copper tube, producing half a volt, and used to electro-plate a small finger sized silver statue with gold when immersed in a cyanide-gold solution, a plating thick enough to deceive museum curators, to mistake the artifact as being made of solid gold.

External links

• "Battery, Baghdad, 250 BC" at the Smith College Museum of Ancient Inventions