This blog is written for my Materials Science students back at UAkron, who are busy learning some chemistry essentials with my co-instructor, Prof. Richard Elliott of our Department of Chemical and Biomolecular Engineering. A few days ago, we hosted two visiting scholars for a two day visit to Ziyaret Tepe: Prof. Thomas Zimmerman, the head of the archaeology department at Bilkent University and Dr. Latif Özen, a chemist and conservator in the Laboratory for Restoration and Conservation at the Museum of Anatolian Civilisations, both in Ankara. Thomas and Latif brought a portable x-ray fluorescence unit (p-XRF) to study the elemental composition of some of our artifacts.
In particular, we were interested in the metal artifacts found in the cremation burials in the Bronze Palace, which we assumed were made of copper alloys, most likely bronze (an alloy of bronze and tin). An artifact is placed on the sensor of the p-XRF and is subjected to a high energy x-ray beam. The sensor monitors the emission of energy by excited atoms on the surface of the artifact (to a depth of 3 microns); the specific characteristics of the energy emitted tells us what atoms are present.
In initial tests, we found that some of our ancient metal artifacts (not from the cremation burials) were nearly pure copper, while others were copper-tin bronze, and at least one was made of an alloy of copper and arsenic (called “arsenical bronze”). We also found that one team member’s “white gold” ring was nickel plated and that my 18K gold wedding band is actually 14K gold since the p-XRF provides a weight percent so we not only what elements are present, but their relative percentages.
Here’s the question for the Materials Science class. All of the artifacts tested initially by Thomas and Latif from the burials had very, very low concentrations of the element vanadium (V, atomic number 23). In their previous analyses of 1500+ artifacts from ancient Anatolia, they did not have evidence for the presence of vanadium in any artifacts and yet it was consistently present in all the artifacts from the cremation burial at Ziyaret Tepe that they initially tested. This was an unanticipated surprise. We subsequently tested earth samples of the burnt lining of two of the cremations and they too had a very, very low vanadium concentration, a few parts per million. In other words, this element is present in the edges of the cremation pits, not just in the metal artifacts.
So, UAkron students, what are some possible explanations for the presence of vanadium in these archaeological contexts and artifacts? What can you tell me about vanadium’s properties, occurence in nature, and the various states in which it occurs? The concentrations are a fraction of a percent, so it is a trace element in these artifacts.
Disclaimer: these results are only very preliminary and need statistical analysis to verify and to provide us with more precise estimates of the concentration. Likewise, Thomas and Latif continued their analyses after leaving the dig house, working in the museum until their flight home to Ankara, so there are some analyses for which I have no information about at all. It’s an interesting little chemistry puzzle for the beginning of the semester. I’ll pass along any other details as they emerge.