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27 Nov

It is expected then, for a 5,570 year (1 half-life) or 11,140 year old (2 half-lives) sample that 125 or 63 counts per second would be obtained.

Ages are calculated using 5568 years as the half-life of radiocarbon and are reported without reservoir corrections or calibration to calendar years.Plant/wood and charcoal samples undergo a series of heated acid-base-acid leaches to remove inorganic carbon and mobile organic acid phases. We will repeat up to 20 base leaches; even if the solution is not clear after 20, we stop the base treatment and move on to a final acidification.Sediment samples undergo the acid pretreatment only.For small samples, blank contribution as a fraction of sample mass becomes a more important term, so a mass balance blank correction is applied.This correction is performed as follows: $$Fm_ = Fm_ ( Fm_ - Fm_b)\frac$$ Where $$M$$ is sample mass, and $$M_b$$ and $$Fm_b$$ are the mass and Fm of the blank.At the present time, for a 1 milligram sample of graphite, this limiting age is about ten half-lives, or 60,000 years, if set only by the sample size.However, limiting ages or "backgrounds" are also determined by process blanks which correspond to the method used to extract the carbon from the sample.While the three carbon isotopes are chemically indistinguishable, lighter C, reflecting the difference in mass.Fractionation must be corrected for in order to make use of radiocarbon measurements as a chronometric tool for all parts of the biosphere.The Fraction Modern corrected for δC of a sample 10 separate times over the course of a run.The final reported error is the larger of the internal or external error, propagated with errors from the normalizing standards and blank subtraction.