An absolute dating technique that depends on measuring the chemical composition of a specimen. Chemical dating can be used when the specimen is known to undergo slow chemical change at a known rate. For instance, phosphate in buried bones is slowly replaced by fluoride ions from the ground water. Measurement of the proportion of fluorine present gives a rough estimate of the time that the bones have been in the ground. Another, more accurate, method depends on the fact that amino acids in living organisms are l-optical isomers. After death, these racemize and the age of bones can be estimated by measuring the relative amounts of d- and l-amino acids present.
Subjects: Chemistry — Biological Sciences.