Send charcoal for carbon dating

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How It Works: Carbon has 3 isotopic forms: Carbon-12, Carbon-13, and Carbon-14.

The numbers refer to the atomic weight, so Carbon-12 has 6 protons and 6 neutrons, Carbon-13 has 6 protons and 7 neutrons, and Carbon-14 has 6 protons and 8 neutrons.

But most archaeologists are not chemists or physicists, so we often collect and send our samples to specialist laboratories, and then wait weeks or months before we receive an email with results of the analysis with limited understanding of what goes on in the meantime.

Sometimes these samples are sent off accompanied by a whispered prayer to the universe: I’ve collected and sent many samples for analysis before, but this week I was fortunate enough to travel to ANSTO to meet their researchers and learn how charcoal samples are prepared and pre-treated for analysis.

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It’s a fairly straightforward process – even for a non-chemistry-minded person such as myself – similar to following a recipe (albeit one that involves sterile facilities and acids! Pre-treatment involves scraping the outside off the charcoal sample, then treating it with acid, then an alkali solution, and then acid again.

The sample is then dried and repackaged into small glass vials before being combusted at around 900°C.

So that’s been my work for this week: travel to a facility on the other side of the country, and a week in a small, sterile lab learning a new skill. As I post this, I’m packing up and getting ready to head back to the airport to fly home.

This opportunity is courtesy of an AINSE research grant, and means that I’ve been able to work on samples I collected during my fieldwork last year.

ANSTO uses an isotope analysis technique called “Accelerator Mass Spectrometry”, or AMS, for radiocarbon analysis, which involves firing a sample of carbon through a particle accelerator to measure carbon isotope ratios.

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