Lead used in metallurgy is extracted from ore containing radioactive elements, especially uranium. It generates lead 210 which has a half life of 22.3 years. Thus, during the extraction process, lead contains lead 210, whose quantity decreases by half every 22.3 years. Therefore, its content is virtually undetectable after about 130 years. It results from this phenomenon that “old” leads no longer contain enough lead 210 to be detected. This method thus allows to determine whether lead in an alloy comes from a modern metallurgy or not.
A fragment of low mass (less than one hundred of milligrams) is prepared to extract the lead analyzed by alpha spectrometry (indirect measurement of lead 210 from the activity of polonium 210). The measurement is compared with a marquor of calibration to quantify the lead 210 present in the alloy and thus, determine the antiquity of the fabrication of the alloy.
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