Carbon dating example
It is possible to detect if there has been any degradation of the sample by comparing the relative volume of each amino acid with the known profile for bone.
If so, separating the amino acids may be necessary to allow independent testing of each one—agreement between the results of several different amino acids indicates that the dating is reliable.
The gas was then condensed, and converted to calcium carbonate in order to allow the removal of any radon gas and any other combustion products such as oxides of nitrogen and sulphur.
The calcium carbonate was then converted back to again, dried, and converted to carbon by passing it over heated magnesium.
The recrystallized calcium carbonate is generally in the form of calcite, and often has a powdery appearance; samples of a shiny appearance are preferable, and if in doubt, examination by light or electron microscope, or by X-ray diffraction and infrared spectroscopy, can determine whether recrystallization has occurred.
In cases where it is not possible to find samples that are free of recrystallization, acid washes of increasing strength, followed by dating part of the sample after each wash, can be used: the dates obtained from each sample will vary with the degree of contamination, but when the contaminated layers are removed, consecutive measurements will be consistent with each other. The process takes about a month, and requires a sample about ten times as large as would be needed otherwise, but it allows more precise measurement of the For samples in liquid form, for use in liquid scintillation counters, the carbon in the sample is converted to benzene, though other liquids were tried during the early decades of the technique.
Hydrochloric acid was added to the resulting mixture of magnesium, magnesium oxide and carbon, and after repeated boiling, filtering, and washing with distilled water, the carbon was ground with a mortar and pestle and a half gram sample taken, weighed, and combusted.
Before this can be done, however, the sample must be treated to remove any contamination and any unwanted constituents.
It is also possible to test conchiolin, which is an organic protein found in shell, but this only constitutes 1-2% of shell material. Libby's first measurements were made with lamp black, The steps to convert the sample to the appropriate form for testing can be long and complex.
To create lamp black, Libby began with acid washes if necessary to remove carbonate, and then converted the carbon in the sample to , and then dried to remove any water vapour.
Wood contains cellulose, lignin, and other compounds; of these, cellulose is the least likely to have exchanged carbon with the sample's environment, so it is common to reduce a wood sample to just the cellulose component before testing.
However, this can reduce the volume of the sample down to 20% of the original size, so testing of the whole wood is often performed as well.Carbon-14 dating is a way of determining the age of certain archeological artifacts of a biological origin up to about 50,000 years old.