Abstract
FIVE isotopic forms of the element carbon are known, having atomic weights ranging from 10 to 14. Two of them, C12 and C13, exist stably in Nature, while the others are radioactive, and are known to us only through their production in various nuclear reactions. The recent great development in the techniques of isotope separation have made it possible to produce substantial quantities of carbon compounds in which the ratio of C3 to C12 has been increased far beyond the 1.1 to 98.9 characteristic of natural carbon. This will be important in chemical and biological research, for C13, being chemically the same as natural carbon, but distinguishable from it by the sensitive techniques of massspectrography, may be used as a 'tracer to follow the history of carbon atoms in their passage through chemical and biochemical reactions. For example, if a small quantity of C13-enriched sugar is eaten by or injected into an animal, the distribution and state of chemical combination of the carbon of this particular dose may be determined by measuring the C13-C12 ratio of appropriate specimens taken from the animal at a later date. The importance of C13 is all the greater because two of the three radioactive isotopes of carbon decay too rapidly to be suitable tracers, while the remaining one (C14) has so long a life (3,000 years) that its detection by radioactive methods is relatively insensitive.
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Carbon-13. Nature 157, 71 (1946). https://doi.org/10.1038/157071a0
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DOI: https://doi.org/10.1038/157071a0