Carbon-14 measurements are made by taking a known amount of carbon,
reducing it to a gas, and then counting the ¹⁴C disintegrations in the
gas. This may sound simple, but in reality the measurement process is a
formidable undertaking, because the amount of the ¹⁴C isotope in the
carbon is so extremely small. (The remainder of the carbon, of course,
consists of other isotopes—¹²C or ¹³C, which are stable.)
There are two basic techniques. The carbon can be: