1. Archaeological studies of underwater sites have special considerations for id
ID: 631719 • Letter: 1
Question
1.
Archaeological studies of underwater sites have special considerations for identifying artifacts. For objects that cannot be brought up to the surface for analysis, atomic emission using a high powered laser as the excitation source is a useful technique. On one exploratory dive, a field worker discovered a large piece of yellowish-brown colored metal on the seafloor and used a portable laser spectrometer to take a spectrum, which is shown below.
Based on the location and other artifacts nearby, the team believes this artifact to be composed of one of four possible metals:
Table 1: Suspected Metals
Alloy
Primary Components
Trace Components
Jewelry Gold
Cu, Au
Zn
Sterling Silver
Ni, Ag
Mg, Cu
Electrum
Au, Ag
Cu
Bronze
Cu, Sn, Zn
Pb, Mg
BAg-37
Cu, Ag, Zn
Sn
Using the spectrum above and the reference table below, determine which of the possible metals this sample is made of.You can click on the image to open it in a new window. You may find it helpful to zoom in on it, depending on your monitor size.
Table 2: Major Emission Lines, 268-288 nm
Element
Emission Line Wavelength(nm)
Cu
270 (b)
276.6
282.4
Au
274.8
280.2
282 (b)
288.4
Pb
280.2
283.3
Mg
279.6
Ni
280.5
282.1
286.4
Ag
272.2
276.8
282.5
Sn
284.0
286.3
Zn
275.6
277.1
280.1
(b) indicates a broad peak or band.
(HINT: Watch out for spectral interference!)
Which metal has the diver found?
Au
274.8
280.2
282 (b)
288.4
Answer
Jewelry gold
Sterling silver
Electrum
Bronze
BAg-37
More than one choice is possible; further analysis is required.
Table 1: Suspected Metals
Alloy
Primary Components
Trace Components
Jewelry Gold
Cu, Au
Zn
Sterling Silver
Ni, Ag
Mg, Cu
Electrum
Au, Ag
Cu
Bronze
Cu, Sn, Zn
Pb, Mg
BAg-37
Cu, Ag, Zn
Sn
Explanation / Answer
Jewelry gold with alloy of bronze
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