The Baghdad Battery

Galvanic cell
The Baghdad battery in the Museum 

With good reasons i can say that archaeology has helped us have an in-depth understanding about a lot of things around us, at some point it also gives us some sort of a hint on how to improve them let's say Electricity. When we think of electricity, we recall Benjamin Franklin and his metal key-kite discovery in 1752 but what if electricity existed before the Benjamin Franklin's discovery like about 2000 years earlier, that's a very big time difference and that brings up this summary facts about the Baghdad battery.

Discovered in Khujut Rabu, Iraq near the metropolis of Ctesiphon , the capital of the Parthian around 250 BC and 224 AD which the battery was said to be originated from but has the pottery style of the Sassanid period 224-640 AD. The artifact was a 130mm terracotta pot, in it was a cylinder made of rolled copper sheets with a single iron rod in the middle. The top of the iron rod was isolated from the cylinder by bitumen and had stoppers, the cylinder wasn't watertight so any liquid added to the pot will eventually touch the rod as well. Researchers hypothesized that this artifact was a galvanic cell used for electrotherapy or electroplating but there wasn't any electrogilded object from the time period it was built.

Baghdad battery
The artifact's main components: the terracotta pot, cyclinder copper sheets and the Iron rod

In 1938, an assistant in the National Museum of Iraq wrote a book explaining his hypothesis on how the artifact was a galvanic cell used for electroplating gold onto silver objects. His explained hypothesis was rejected by skeptics, Sad. Many other speculations from people about the artifact been a battery believed that as it wasn't watertight, grape juice and vinegar (and other natural acidic substance) was used to used as an acidic electrolyte solution to create an electric current due to the difference between the electrode potentials of the copper and iron

Battery hypothesis and research proved the artifact wasn't useful as a battery because bubbles form a partial insulation of electrode due to the gas evolved in the iron,copper, electrolytes junction so the battery's efficiency decreases the more it is used and the voltage created by that combination is below 1 volt. Again, if the bitumen seal was supposed to serve as an insulator it would be very inconvenient for a galvanic cell because it's thermoplastic and require constant topping if they planned to use it for long. This artifact was initially mistaken to be another known artifact, The Seleucia vessels used for storing sacred scrolls because they looked identical. No one has fully understood this Baghdad artifact, its actual origin and purpose is still unclear. Let me hear your speculations in the comment section.


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