Secrets hidden in a jar
The Baghdad Battery (or Parthian Battery) is believed to be an artifact dating back to the dynasty of the Parthians (247 AC -224 AD) discovered in 1936 in the village of Khuyut Rabbou'a in Iraq, and found in 1938 by Wilhelm König, amid a pile of abandoned finds in the basement of the National Museum of Iraq.
It was König himself, once returned to Berlin (1940) to write a booklet in which he hypothesized that he could treat a primitive galvanic cell, perhaps used to plaque with a subtle golden patina some silver objects, forerunner, therefore, of the electrochemical cell by Alessandro Volta of about 1800 years. This possibility raised two great questions: Were the Parthians to invent the battery? Are we face an OOPArt?
How is the Baghdad Battery made?
The artifact looks like a terracotta jar of about 13 cm of height containing a cylinder consisting of a thin rolled copper sheet, which in turn contains an iron bar, isolated from the cylinder through an asphalt cap.
As the cylinder was not watertight, the electrolyte solution could reach no obstacles in contact with the iron bar. The level of corrosion of the internal components has led some scholars to suppose that, as an electrolytic solution, vinegar, lemon juice or grape juice could be used.
Most battery components are not directly datable as the thermoluminescence could reveal only the date of cooking of the ceramic vessel and not its assembly, while the study of the dissemination of the ions would only indicate the date of burial.
König assumed that the object could have been built during the domain of the Parthians, as the portion of the village where he had been found back at that time, but Dr. St. John Simpson, of the Department of the Near East of the British Museum, believes not only that there were errors in his stratigraphy and in the consideration of the original context of the site but also that the style of ceramics is Sasanide therefore attributable to a more recent dating.
The tests on operation
Many experiments have tried to demonstrate the electrical capabilities of this artifact:
as any object composed of two different metals immersed in an acidulous solution can function as a rudimentary pile but, in this way, the generated current is minimal and not sufficient to make the pile work more than a few minutes if the two metals are copper and iron, unless you use acid solutions unknown at the time.
Various types of electrolytes were proposed, based on known substances at that time but, being the object found by König a hermetically closed cylinder, could have worked at most for a few minutes.
The experiments carried out by W.F.M. Gray with copper sulphate and Jansen and other researchers with benzochinone (a substance found in secretions of some centipedes and beetles) mixed with vinegar, do not work satisfactorily with the Battery of Baghdad because there is something missing in it that separates the electrolytes that react with the two electrodes.
In 1980, Egyptologist Arne Eggebrecht created a voltaic cell using a vessel filled with grape juice, obtaining the production of half volt of electricity and demonstrating that it is possible to plated a figurine of silver in two hours, using a solution of gold and cyanide.
In the program "Mythbusters", ten terracotta jar replicas were connected in series, acted by batteries producing 4 volts of electricity thanks to the lemon juice used as an electrolyte to activate the electrochemical reaction between copper and iron. The transmission suggested three possible uses for the artifact: galvanization, medical use (electro-acupuncture) and religious experience.
To "test" the religious experience was built a replica of the Ark of the Covenant with cherubs whose wings were connected to an electric generator: those who touched the ark felt a strong sense of oppression to the chest. Even if the "Baghdad Batteries" were not used, it could be assumed that their low power would still generate in the faithful, who had no idea of electric current and its effects, the feeling of a "divine presence".
The possibility that the object was a rudimentary battery exists and is not unthinkable for the technical possibilities of time although, today, the theory of its use for plating objects is considered unlikely: Paul Craddock of the British Museum, remembers from this region have survived only objects with conventional gilding and mercury gilding.
Against the electrical thesis
Even the test cited by König, i.e. that even today the craftsmen of Baghdad use a particular galvanic gilding technique, was excluded as the technique used in Iraq is very different from the electrochemistry present in the Battery as it contains zinc, much more oxidable than Iron, and salts of cyanide, unknown in ancient times.
Tests performed by Arne Eggebrecht have shown that "many" cells are needed to make a plating of just a micrometer: the power generated by the artifact would be too low to fulfill this function.
The asphalt that covers the "vessel" is totally so much that the object must be changed to ensure that the electrons can circulate; it also would also need constant maintenance to work.
Archaeologist Ken Feder points out how the artifact does not own external conductive wires that can indicate links between the vessels for their use.
Many noted the similarity between the artifact and the containers used in nearby Seleucia near the Tigris River to carry the sacred scrolls, whose decomposition, creating an acidic environment, would have been the cause of the deterioration of the internal elements.
Paul Keyser hypothesized that a priest could use the cell to amaze the faithful by electrifying metal statues or for a kind of electro-acupuncture therapy: in ancient times the current produced by eels was used to soothe pain or anesthetize an area of the body for medical care.
In the light of the discovery of some bronze and iron needles in Seleucia together with the batteries, it can be assumed that the device has been used for acupuncture sessions, a very common practice also in China of that period.
OOPArt: Yes or no?
Some claimed that the Baghdad battery is proof of how electricity was already known in antiquity. Others however stress that, even being able to verify its actual nature of the electrical device, the knowledge of the existence of electrical phenomena does not necessarily involve a real understanding. In the texts of the parts there were no references to these phenomena or to their direct use have not been identified. It may be that the "batteries" were used only in a mystical context.
"A battery by definition is a collection of cells. So the cell is a little can of chemicals. And the challenge is taking a very high-energy cell, and a large number of them, and combining them safely into a large battery."
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