All language subtitles for 13 TheCarbon1414Cdatingmethod

for this segment

I like to introduce Doctor Stuart Fallon

who is the head of the Radiocarbonating Laboratory

at the Australian National University

the first step is to drill a bone

and collect the powder

we then do tests that verify

the bone is suitable for dating

though in the chemistry laboratory

um we dissolve the bones with the dilute acid

so we can isolate the collagen

the collagen is the organic protein in bone

that is the most robust

and most suitable for radiocarbon dating

the next step is we take the cleaned collagen sample

and we freeze dry it to remove

all of the water from the sample

after freeze drying we end up with nice pure

clean fluffy collagen

the next step is

we have to convert the collagen to carbon dioxide

and to do this

we weigh out 2 milligrams of collagen

and we load it into a quartz tube

inside the quartz tube

we add copper oxide and silver

copper oxide provides oxygen

to generate the carbon dioxide

now we load the sample on a vacuum line

or evacuate all of the air out of the quartz tube

we then use a flame torch to seal the tube

with our pure collagen sample inside

we next put the samples into the oven at 900 degrees

for six hours

this is to make CO2 inside the quartz tubes

the first step is to load the quartz tube

onto the vacuum line

we evacuate

or remove all of the air from around the tube

and then we crack the sample

we isolate the carbon dioxide using liquid nitrogen

which is cold enough to freeze

carbon dioxide into a solid

we transfer the carbon dioxide

into an individual reactor

we then add hydrogen to the carbon dioxide

we heat it at 560 degrees

and after two hours

the carbon dioxide has turned into elemental carbon

or graphite

we then take the graphite

and we press it into our small aluminium sample holders

now we will load

the samples into the accelerator msptrometer

our sample wheel holds 39 samples

inside we have a mixture of standards

secondary standards

blank samples and our unknown samples

let me show you

how the accelerator mass spectrometer works

our graphite samples are inside our iron source

in the ion source

we heat up cesium

which is a metal

the positive cesium ions interact with the graphite

and generate negative carbon ions

these ions are accelerated to 44,000 volts

the ions are then separated in a magnetic field

or a mass spectrometer

where we can separate out carbon 12

carbon 13 and carbon fourteen

the ions and molecules

which are also in the beam

are further accelerated to 245,000 volts

the ions and molecules then go through

a cloud of helium gas

where all the molecules are broken up

the beam then goes through another magnetic field

or the second maspektrometer

in the accelerator maspektrometer

where we can measure carbon 12 and carbon 13

carbon 14 is further filtered by an energy filter

and we measure each carbon 14 atom as it hits a

silicon detector